3

042-18-25.1.55/03-2016

"Basis of biochemistry "

1

8 2016 .

-

"Basis of biochemistry "

5BB080100 Agronomy

5B080700 Forests and forestry

5B080300 Hunting study and fur-farming

5B080200 Technology of production animal products

5B060800 Ecology

5B073100 Health and safety and protection of environment

5B120100 Veterinary medicine

5B120200 Veterinary Sanitation

-

2016

1 3

2 5

3 154

4 194

5 218

1. The conceptual apparatus

"Rule of 10%" (rule of the pyramid energy R. Lindemann): from one trophic level ecological pyramid moves to another higher its level (the "ladder" producer - consumer), on average, about 10% received the previous uroven energy .

Abiotic factors - factors of inanimate nature (cosmic, geophysical, climatic, spatial, temporal, etc.) that have a direct or indirect impact on living organisms.

Act of tolerance (V.Shelford): environmental factors, with specific conditions pessimal (unfavorable as a minimum, and excess) value that limits the ability of the species in these conditions, in spite of and in spite of the optimal combination of certain other conditions.

Agrocenoses - community of organisms cultured and accompanying them in agriculture.

Amensalizm - type of interspecies relationships, in which in a joint environment, one kind of organism suppresses suschestvovanie another species without experiencing resistance.

Anthropogenic factors - factors that have arisen as a result of human activity.

Autotrophs - organisms can synthesize organicheskoe agent of carbon dioxide, water and salts mineralnyh. energy sources are used for the biosynthesis of light (in photoautotrophs) or oxidation of a number of inorganic substances (in chemoautotrophs).

Bio-accumulation - the accumulation of substances (man-made pollutants) in the body increasing trophic levels.

Biogen - a nutrient; nutrients, nutrients essential chemical elements that make up the substance of living organisms, carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus.

Boreal zone - the zone of temperate forests.

Chemosynthesis - synthesis of organic substances in chemoautotrophic bacteria using as power sources of certain inorganic oxidizing substances.

Co-evolution - in parallel, the joint conjugate evolution of mankind and nature.

Consuments - heterotrophic organisms (mostly animals) who consume organic matter other plant organisms (herbivores - herbivores) and animals (carnivores - zoophages).

Cryostasis - temporary total suspension of the body's vital functions associated with the onset of unfavorable conditions or with extreme phase of individual development.

Depopulation - a reduction in population, population.

Desertification (aridity) - the process of depletion of vegetation associated with a persistent reduction in moisture areas, its transformation in the arid zone, topically, followed by the previous member of the chain.

Detritophages - organisms that feed on detritus (saprophagous).

Detritus - dead organic matter, isolation and decay organisms products.

Disadaptation - violations of vital activity caused by the incompleteness of acclimation, the inability to fully adapt to changing environmental conditions.

Dissimilation - the disintegration of complex organic substances in the body, accompanied by the release of energy, which is used in the processes of life.

Ecological culture - system of scientific knowledge about the human interaction of society and nature; environmental value orientations, rules and regulations; moral and aesthetic attitude towards nature; skills for the study of nature and its protection.

Edafon - a set of soil animal population of the Earth's thermal radiation air.

Education - a relatively meaningful and purposeful nurturing person in accordance with the specific objectives of groups and organizations, in which it is carried out.

Ektotermy - organisms, the body temperature is a little different from the temperature of the environment and follow its changes: lower organisms, plants, cold-blooded animals.

Emergence - the emergence of completely new properties of the interaction of two or more objects or phenomena, properties that are not simply the sum of the original.

Endotherm - warm-blooded animals birds and mammals, are capable of using the internal mechanisms of thermoregulation to maintain a relatively constant body temperature, to a certain extent independent of the ambient temperature. "

Environmental - trudnosti crisis, environmental problems due to anthropogenic human activities.

Environmental education - the formation of the human conscious perception of the environment, the conviction of the need for respect for nature, rational use of its wealth of natural resources.

Environmental education - tselenapravlennaya specially organized, systematic educational activities aimed at the development of environmental education and upbringing of children, on the formation of environmental awareness and skills for the study of nature and its protection.

Environmental education and training of students - pedagogical process, which ultimately should provide insight into the importance of proper behavior in the natural environment, the ability to anticipate and assess the impact of its activities, the realization that the man part of nature /

Environmental upbringing - purposeful human development, including the formation of its ecological culture, the perception of not only the public, but also of environmental norms and values;

Eurybionts (evrieki) - organisms that exist in a wide range of changes in environmental conditions: temperature (evritermy), humidity (evrigidridnye organisms), food choices (euryphages), etc.

Eutrophication - the excessive enrichment of water with nutrients.

Gene flow - the process of undirected random changes in gene frequency in a population.

Heterotrophic organisms - organisms that feed on organic matter ready.

Hibernation - a significant reduction in the level of life upon the occurrence of adverse external conditions (for example, hibernating animals).

Homeostasis - the ability of an organism or organisms of the system to maintain stable dynamic equilibrium in a changing environment.

Humid Zone - area or natural-climatic zone with high

Law of constancy of the amount of living matter of the biosphere (Vernadsky): The number of living matter (biomass of all organisms) for the biosphere of the geological eras.

Noogenesis (noospherogenesis) - the process of formation of the noosphere.

optimality law: any system with the highest efficiency in the functioning of some specific spatio-temporal limits to her.

Phenotype - a set of genetically determined characteristics and properties of the organism.

Photoperiodism - change the state of biological systems due to the natural rhythm of light exposure, the change of day and night, seasonal changes in the length of daylight.

Phytocoenosis - multispecies plant community.

Phytophagy - herbivorous animals.

Phytoplankton - a set of micro-algae, small plant organisms that live in the water column

Rule D.Allena: increase protruding body parts of one species or closely related species of warm-blooded animals (limbs, tail, ears) when moving from north to south.

Rule K.Bergmana: warm-blooded animals, subject to geographical variation, the body size of individuals statistically (on average) more than in populations living in colder parts of its range.

Security Environment - the degree of protection of the territorial complex ecosystems, the human potential of the eco-logical lesions derived from the magnitude of environmental risk.

Technosphere - "technical envelope" - artificially transformed space of the planet, being under the influence of human industrial activity products.

The capacity of the ecosystem - the maximum size of the population of one species, this ecosystem which is capable of supporting in certain environmental conditions for a long time.

The law of irreversibility of evolution (L. Dollo): evolution is irreversible; organism (population, species) can not return to their previous state, already implemented in a number of his ancestors.

The noosphere - the letters "thinking envelope", the scope of reason; according to Vernadsky - a qualitatively new, higher stage of development of the biosphere under the control of a reasonable human activity.

The ontogenesis - the individual development of the organism; multicellular egg from fertilization to aging and death.

Valence Environment - (tolerance limits) the characteristic type of ability, populations exist in different

Valeology - science for the preservation and strengthening of health, healthy lifestyles.

Zoophages - carnivorous organisms that feed on other animals or their species (cannibalism).

Environmental education - process of mastering by students the system of scientific knowledge about the natural environment as the reality of human life, about the impact of industrial activity on the environment of society, as well as the knowledge and skills of environmental activities.

Environmental awareness -environmental knowledge (information, conclusions and generalizations) about the natural environment and interacting with her man, ecological thinking, feeling and will.

Environmental science is a generic of the relation of organisms in the environment (Haeckel), the science of organization and functioning supraorganismal systems at various levels: the populations of species, biocenoses (communities), ecosystems and the biosphere.

2.Lectures

Module 1.Introduction.

Biochemistry subject

The main principles of chemical logic of a live condition. The concept about macro- and microelements.

I. Basic Chemical Concepts

A. Atoms

1. Def.- the smallest unit of an element that can combine chemically with other elements

Structure

a. Proton (+) charged

b. Neutron (not charged)

c. Electron (-) charged

1. Electrons exist in distinct orbital clouds

2. s, p, and dorbitals

3. Orbitals combine to form energy levels: K, L, M, N, etc

d. Protons and neutrons are the same mass and make up the nucleus

2. Identification

a. Atomic number: number of protons

b. Atomic mass number: number of protons + neutrons

c. Atoms are organized into groups in theperiodic table

3. Isotopes

a. Two atoms with the same atomic number but different atomic mass numbers

b. Differ only in the number of neutrons

c. Some are radioactive (radioisotopes)

B. Compounds

4. Def: a combination of two or more elements which are joined chemically

5. Chemical bonding

a. Ionic: when an atom will eithergive or takean electron from another atom

1. Cation: positive ion

2. Anion: negative ion

3. Electrostatic forces hold the atoms together

b. Covalent: when atoms share electrons

1. Forms single or multiple bonds

2. Sharingof electrons hold the atoms together

c. Hydrogen bonds: weak links between the hydrogen (+) end of onepolar moleculeand the negative end of another polar molecule

C. Acids and Bases

6. Acid: a substance which releases a H+ ion

7. Base: a substance which releases an OH- ion

8. pH scale

a. A method of determining how acidic or basic a solution is

b. Negative logarithmic scale: 0 (acidic) to 14 (basic) (alkaline)

c. pH 7.0 is neutral (water)

9. Buffers: a substance which limits the change of pH

D. Basic chemical reactions

10. Synthesis: two or more atoms or molecules are combined

11. Decomposition: molecules are broken down into simpler forms

12. Reduction

a. The addition of electrons to a molecule

b. Often accompanied by a gain of a hydrogen nucleus (proton)

13. Oxidation

a. The removal of electrons from a molecule

b. Often accompanied by a loss of a proton

c. Oxidized atoms are more reactive than reduced atoms

II. Basic Biochemistry Concepts

A. Building Materials of Life

1. Inorganic compounds

2. Organic compounds

a. All contain some form of carbon

b. Biosynthesis: the manufacture of things by a living organism

3. Carbohydrates

a. Structure

1. Contain only C, H, and O

2. Ratio of O:H is 1:2 (same as water H2O)

b. Reactions involving carbohydrates

1. Dehydration synthesis: joining two molecules by removing water

2. Hydrolysis: splitting two molecules by adding water

c. Types

1. Monosaccharides (simple sugars)

a. 5-carbon: ribose

b. 6-carbon: C6H12O6(Glucose, Galactose, Fructose)

2. Disaccharides

a. Two monosaccharides joined together (dehydration synthesis)

b. Sucrose (table sugar): Glucose + Fructose

c. Maltose (malt sugar): Glucose + Glucose

d. Lactose (milk sugar): Glucose + Galactose

3. Polysaccharides

a. Starch: straight chain of glucose (food storage in plants)

b. Glycogen: branched chain of glucose (food storage in animals)

c. Cellulose: Zig-zag chain of glucose (non-digestible roughage)

4. Lipids

a. Fats (triglycerides)

1. 3 fatty acid molecules + 1 glycerol joined by dehydration synthesis

2. Saturated: no double bonds between carbons

3. Unsaturated: at least one double bond

b. Phospholipids

1. 2 fatty acids + 1 glycerol + 1 phosphate

2. Hydrophobic end (fat): water fearing (non-polar)

3. Hydrophilic end (phosphate): water loving (polar)

4. Used extensively incell membranes

c. Sterols: multi-ringed compounds

1. Cholesterol

a. HDL: High density lipoprotein ("good" cholesterol)

b. LDL: Low density lipoprotein ("bad" cholesterol)

2. Hormones: i.e. prostaglandins, cortisone, etc

5. Proteins

a. Structure: composed of 20 basicamino acids

b. Protein synthesis

1. Two amino acids are brought together anddehydration synthesisbetween the amino acids forms a peptide bond

2. Protein =polypeptide chain

3. Theorderof the amino acids is critical to the function of a protein

c. Enzymes: large proteins which catalyze reactions

1. Structure

a. Active site: attachment site for substrates

b. Substrate: molecule which reacts with the enzyme and is changed

c. Coenzyme: non-protein which helps to complete the active site (vitamins)

2. Enzyme action

a. Enzyme & substrate bind at the active site

b. Reaction proceeds (lytic- splitting apart, synthetic - putting together)

c. Enzyme and product(s) separate

6. Nucleic acids

a. Consist of long chains of repeating subunits (nucleotides)

b. Nucleotide structure

1. 5-carbon sugar (ribose)

2. Phosphate group (PO4)

3. Organic nitrogen-containing base

c. DNA: Deoxyribonucleic acid

1. Used to store biological information

2. DNA base pairs

a. Guanine - Cytosine (G - C)

b. Adenine - Thymine (A - T)

3. Double-stranded helix shape formed byhydrogen bonds

d. RNA: Ribonucleic acid

1. Used as working blueprints for protein synthesis

2. RNA base pairs

a. Guanine - Cytosine (G - C)

b. Adenine - Uracil (A - U)

3. Single strand

III. Energy and its Changes

A. Kinetic energy: energy of motion

B. Potential energy: energy of position (stored energy)

C. Kinetic and potential energy are interconvertable

D. Energy in chemical reactions

1. Exothermic: reactions which release energy (heat)

2. Endothermic: reactions which require energy

3. Activation energy: energy needed to start a chemical reaction

Module 2.Aminoacids.

Amino acids: classification, structure, stereochemistry, physical and chemical properties and classification amino acids forming proteins.

Properties of the 20 amino acids that occur in peptides and proteins are crucial to the structure and function of proteins.

stereochemistry

relative hydrophobicity or polarity

hydrogen bonding properties

ionization properties

other chemical properties

Condensation of 2 amino acids forms the peptide bond, the amide linkage holding amino acid residues in peptide and protein polymers.

Properties of the peptide bond have major consequences in terms of the 3-dimensional structures of proteins

There's an excellentwebsite on amino acidsbeing developed here in the Department of Biochemistry and Molecular Biophysics; parts of it are still under construction, but there are links to various very useful parts of it here in these notes, and indeed parts of it may be used in class.

BASICS

Proteins are polymers of-amino acids:

There are 20 different amino acids found in proteins and they differ by the nature of the R group.

Both the-amino group (amino group substituent on theC) and the-carboxyl group (carboxyl substituent on theC) areionizable.

-COOH group: a weak acid, can DONATE its proton, with a pKa of about 2-3.What's the conjugate base form of the carboxyl group? Which form is charged, and is it a positive or a negative charge?

-NH2group: a weak base (there's an unshared pair of electrons on the N; the neutral amino group can ACCEPT a proton).What's the conjugate acid form of the amino group? Which form is charged, and is it a positive or a negative charge?

pKas of-amino and-carboxyl groups are different for different amino acids, and also are altered if they're the terminal groups on a chain of amino acids, i.e., a peptide or protein.

Predominant form in H2O is thezwitterion:.

Stereochemistry of the amino acids

-carbon is asymmetric (has four different substituents) except for one amino acid, for which the R group is a hydrogen atom.

amino acids occur asenantiomers (nonsuperimposable complete mirror images)

L-amino acidsare the naturally occurring enantiomers found in allproteins

There are naturally occurringD-amino acids, butnot in proteins(found in some bacterial cell wall peptide structures, in some peptide antibiotics, etc.)(D_L)

Perspective formulas show stereochemistry; projection formulas CAN be written "correctly", with convention that horizontal bonds project out of paper and vertical bonds behind plane of paper, but often biochemists use projection formulas casually (inaccurately), knowing that if it's in a protein, it's always anL-amino acid.

Absolute configurations of D-glyceraldehyde as the reference compound for-amino acids.D- and L- apply only to the absolute configuration around the chiralcarbon; 2 of the 20 amino acids (threonine and isoleucine) have a second chiral center, requiring the RS system to describe their structures accurately, but we aren't going to worry about using the RS system here.

Which of the amino acids does NOT have a chiral center, so has no D/L isomers?

Amino Acid Abbreviations

amino acid (or residue in protein)

3-letter abbreviation

1-letter abbreviation

Mnemonic for 1-letter abbreviation

Glycine

Gly

G

Glycine

Alanine

Ala

A

Alanine

Valine

Val

V

Valine

Leucine

Leu

L

Leucine

Isoleucine

Ile

I

Isoleucine

Proline

Pro

P

Proline

Methionine

Met

M

Methionine

Phenylalanine

Phe

F

Fenylalanine

Tryptophan

Trp

W

tWyptophan (or tWo rings)

Tyrosine

Tyr

Y

tYrosine

Serine

Ser

S

Serine

Threonine

Thr

T

Threonine

Cysteine

Cys

C

Cysteine

Aspartic Acid

Asp**

D

asparDic acid

Glutamic Acid

Glu*

E

gluEtamic acid

Asparagine

Asn**

N

asparagiNe

Glutamine

Gln*

Q

Q-tamine

Histidine

His

H

Histidine

Lysine

Lys

K

(beforeL)

Arginine

Arg

R

aRginine

* Glx= either acid or amide (when it isn't known which it is)**Asx= either acid or amide (when it isn't known which it is)

Properties of Amino Acid Side Chains

Side chains ("R groups") provide proteins with unique structural and functional properties.Additional C atoms in R groups (after theC) designated by successive Greek letters:as shown in the structure of the amino acid LYSINE (Nelson & Cox:Lehninger Principles of Biochemistry, 3rd ed., p. 116):

Side chain classes

The side chains of the amino acids play an essential role in determining the properties of proteins.

There is a wide diversity in the chemical properties of amino acid side chains, but they can be grouped into classes, sometimes with overlapping "membership" (e.g., tyrosine is both aromatic and hydroxyl-containing). Other classifications are also possible (for example, the 5 classes in textbook, Fig. 5-5, discussed below). You are expected to know all 20 amino acid structures and their R group properties, including ionization properties (see table below with "generic" pKavalues for groups in peptides and proteins and links to titration curves, and thePDFof proton dissociation reactions).

Side Chain Class

Amino Acids

Aliphatic

glycine, alanine, valine, leucine, isoleucine

Cyclic

proline

Aromatic

phenylalanine, tyrosine, tryptophan

Hydroxyl-Containing

serine, threonine, tyrosine

Sulfur-Containing

cysteine, methionine

Basic

histidine, lysine, arginine

Acidic and Their Amides

aspartic acid, glutamic acid, asparagine, glutamine

Nonpolar, aliphatic R groups

Gly: quite water-soluble (as is Pro)

Ala,Val,LeuandIle: increasinghydrophobicitywith increasing number of C atoms in hydrocarbon chain

Pro:cyclic(--> unusual properties)

shares many properties with the aliphatic group

rigidity of ring plays critical role in protein structure (more about that later)

Met: methylthioether (S-containing)

quitehydrophobic

Met's terminal methyl group important in metabolism

Aromatic R groups

Phe:phenylgroup (linked to-CH2, so Phe = alanine with a phenyl substituent on the methylene C)

VERYhydrophobic.

Trp:indolefunctional group onC

electronegative atom in ring system

not as hydrophobic as Phe

hydrogen bonding capability(donor? acceptor? how many hydrogen bonds?)

Tyr:phenylalanine with aromatic OH group (phenolic OH)=p-hydroxyphenylalanine

ionizable(pKaaround 10; loss of proton gives phenolate anion)

hydrogen bonding capability(donor? acceptor? how many hydrogen bonds?)

Tyr R group is the least hydrophobic of the 3 aromatic amino acid side chains.

Polar, uncharged R groups

SerandThr:aliphaticOH groups, not ionizablein pH range 1-13

pKa values so high that under any biologically reasonable pH conditions they'repolar butnotionizable.

hydrogen bonding capability(donor? acceptor? how many hydrogen bonds?)

AsnandGln:amidefunctional groups

VERY polar, butNOT ionizable

hydrogen bonding capability(donor? acceptor? how many hydrogen bonds?)

Cys:thiol(also called asulfhydrylgroup) --notvery polar, andISionizable

sulfur atom makesprotonated -SH groupmore hydrophobic than an aliphatic OH group

thiol DOESlose its protonin physiologically relevant pH range (pKaabout 8.5)

generates-S-(thiolate anionis quite hydrophilic due to the charge).

Positively charged R groups(sometimes called "basic" R groups)

Arg:guanidinogroup

VERY high pKa(~12+), so a very weak acid (stronger base)

carries+ chargeall across physiological pH range

resonance forms of guanidino group stabilize protonated form (charge is delocalized)

hydrogen bonding capability(donor? acceptor? how many hydrogen bonds?)

Lys:-aminogroup (a primary amine)

pKaabout 10

protonated form(predominates at physiological pH) carries+ charge

hydrogen bonding capability(donor? acceptor? how many hydrogen bonds?)

His:imidazolefunctional group (has 2 N atoms in 5-membered unsaturated ring)

pKa about 6-6.5

protonated form carries+ charge, butat pH 7 predominant form is neutral(despite textbook's categorization as "positively charged")

very important player in catalytic activity of many enzymes

hydrogen bonding capability, andalso proton donor/acceptor

Negatively charged R groups(sometimes called "acidic" R groups)

AspandGlu: side chaincarboxyl groups

pKavalues around 4

predominant form at physiological pH =carboxylate anion

hydrogen bonding capability(donor? acceptor? how many hydrogen bonds?)

Relative hydrophobicity/hydrophilicity of amino acid R groups

Table 12.2 : Polarity scale for amino acid residues based on free energy changes for moving a residuefrom a hydrophobic environment (dielectric constant = 2) into H2O.

Similar trends for relative hydrophobicities in text Table 5-1 (diff. numerical scale, and not arranged in order of relative polarity)

Depending on how transfer experiments are done, different absolute numbers can be obtained, but the general trends of relative polarity are clear

Phe, Met, Ile, Leu, Val are very hydrophobic

Arg, Asp, Lys, Glu, Asn, Gln, and His are quite hydrophilic

The rest are in between -- neither very polar nor very hydrophobic

Reversible oxidation of 2 cysteine side chain thiolsto form cystine, or re-reduction to 2 thiols

disulfide bonds between 2 Cys residues in a (usually extracellular) protein

often a critical structural feature in extracellular proteins (stabilize folded structures, in interior of protein structure)

When found inintracellular proteins, usually have afunctional role.

Ionization Properties of Amino Acid Functional Groups (in PEPTIDES AND PROTEINS)

weak conjugate acid/base groups in peptides and proteins crucial to functions

onlyone-aminoandone-carboxylgroup on a peptide or proteins (at the termini of the chain) because the rest of the-amino and-carboxyl groups are tied up in amide bonds holding monomers together in polymer (more later)

side chain ionizable groups (only 7 of the 20 amino acids)

PDFof the acid dissociation reactions for functional groups of amino acid residues in peptides and proteins

ionization states of side chain weak acid groups control charges on protein

Note:local environmentin peptide or protein determinesactualpKa of that specific group, so the ranges shown below (and the rather arbitrary "generic" values, rounded off for simplicity) are only theusualexpected ranges for pKavalues for the functional groups in peptides and proteins; the pKa of a specific group in a specific protein can lie significantly outside the expected range if the local environment is unusual.

linksin table below are totitration curvesfor that amino acid or functional group

Group

usual pKarange, inpeptides & proteins(approx."generic"pKa )

a-Carboxyl(terminal group ofpeptide or protein)

~3.0 - 4.0(generic 3.0)

Asp, Glu(side chain carboxyl)

~4.0 - 4.5(generic 4.0)

His(imidazole)

~6.0 - 7.4(generic 6.5)

Cys(thiol, SH)

~8.5 - 9.0(generic 8.5)

Tyr(phenolic OH)

~9.5 - 10.5(generic 10.0)

a-Amino(terminal group ofpeptide or protein)

~8.0 - 9.0(generic 8.0)

Lys(-amino)

~9.8 - 10.4(generic 10.0)

Arg(guanidino)

~12.0 - 12.5(generic 12.0)

Isoelectric point (pI)

pI= "isoelectric pH" = "isoelectric point" =pHat which theNETcharge on a molecule isZERO.

If pH < pI, net charge ispositive(more + than - charges)

If pH > pI, net charge isnegative(more - than + charges)

pI = the pH exactly halfway between the two pKavalues surrounding the zero net charge equivalence point on the titration curve(examples to be analyzed in class: Gly and His)

Fig. 5-10. Titration curve of glycine (Nelson & Cox:Lehninger Principles of Biochemistry, 3rd ed.)

Molecular separations based on charge properties (paper electrophoresis of amino acids as an example)

paper strip soaked in buffer, in contact with 2 reservoirs with electrodes connected to a power supply

Buffer reservoir #1+(anode; anions move toward it)

O

Buffer reservoir #2_(cathode; cations move toward it)

^Ultraviolet absorbance of amino acid side chains

Aromatic amino acids(Trp, Tyr, Phe)absorb light in the near ultraviolet region of the spectrum (250-300 nm).

Trphas highest molar absorptivity, followed byTyr, withPhemaking only a small contribution.

Disulfide bonds (between Cys residues in proteins) also absorb in the uv range, but much less than the aromatics.

Fig. 5-6(Nelson & Cox,Lehninger Principles of Biochemistry, 3rd ed.): Absorbance of ultraviolet light by aromatic amino acids

Posttranslational modifications of amino acid side chains

chemical modificationsAFTER biosynthesisof proteins

occur for a few amino acid residues insomeproteins

Some examples (see also Fig. 5-8, Nelson & Cox:Lehninger Principles of Biochemistry, 3rd ed.)):

O-Phosphoserine

4-Hydroxyproline

5-Hydroxylysine

-carboxyglutamate

reversible phosphorylation and dephosphorylation of Ser, Thr, and Tyr residues very important in covalent regulation of activity of some enzymes and many biosignalling proteins, including some hormone receptors and transcription factors

4-hydroxyproline & 5-hydroxylysine important in structure of collagen (fibrous protein in connective tissue)

-carboxyglutamate important in a number of proteins whose function involves Ca2+binding, including several proteins involved in blood clotting

Chemical Reactions of Amino Acids

All amino acids have at least two reactive groups: theamino and-carboxyl groups and these groups can react with a variety of reagents. Here are two examples:

A particularly interesting example is thegreen fluorescent protein (GFP) from the Pacific Northwest jellyfishAequorea victoria,which has generated intense interest as a marker for gene expression and localization of gene products. The chromophore, which results from the spontaneous cyclization and oxidation of the sequence -Ser65-Tyr66-Gly67- , is unusual because it does not involve a non-protein chromophore, as is usually the case for colored proteins. The chromophore is buried in the interior ofGFP.

The Peptide Bond

Peptides and proteins:polymers of amino acids joined bypeptide bonds

amidelinkages from condensation of-carboxyl groupof one amino acid with-amino groupof another amino acid

process repeated many times --> linear chain of amino acids, apolypeptide chain

convention: sequence written from left to right starting withresiduewith free-amino group (theN-terminalor amino terminal amino acid residue) and ending with the residue containing the free-carboxyl group (theC-terminalor carboxyl terminal residue),e.g., NH2-Glu-Gly-Ala-Lys-COOH = EGAK

average residue mass ~110 (average Mrof the 20 amino acids minus Mr of H2O)

a polypeptide chain with 100 amino acid residues would have a Mrofabout11,000)

small peptides (a "few" amino acid residues) =oligopeptides

Peptide bond formation endergonic (Go' ~21 kJ/mol)

(How would a cell make the reaction go in the direction of condensation in an aqueous environment? no details needed here for biochemical mechanism -- that's covered in BIOC 411)

peptide bondsmetastablein aqueous environment -- equilibrium lies far in direction of hydrolysis, but RATE of hydrolysis very slow in absence of catalyst

Enzymes that catalyze peptide bond hydrolysis =peptidasesorproteases,e.g., (specific examples of proteases) your digestive proteases like trypsin and pepsin

Ionization properties of peptides

analyzed the same way as for free amino acids

one-amino group (pKaapprox.8)andone-carboxyl group (pKaapprox.3), plus anyionizable side chainson residues in the peptide

To figure out approximate net charge of a peptide at a given pH:

make yourself notes on the sequence to keep track of what you're doing

add up charges on all the ionizable groups

Example:Fig. 5-14(Nelson & Cox:Lehninger Principles of Biochemistry, 3rd ed.): pentapeptide SGYAL = Ser-Gly-Tyr-Ala-Leu= Serylglycyltyrosylalanylleucine

Amino Acid Analysis

Sequence of amino acids in a protein is dictated by the sequence of nucleotides in the gene encoding that protein:

(from Berg, Tymoczko & Stryer, Biochemistry, 5th ed., p. 28)

Each protein (unique sequence) has uniqueamino acid composition.

Can chemically hydrolyze (hot 6N HCl) a pure protein to generate the free amino acids and determine its amino acid composition chromatographically

Because side chains of the amino acids have different properties, can separate and quantitate all 20 amino acids using a variety of chromatographic techniques, as illustrated below.

Peptide bond has resonance structures --> partial double bond character

Due to the partial double bond character of the peptide bond, theO, C, N and H atomsare nearly planar and there is no rotation about the peptide bond (peptide). As we shall see later, the planarity of the these elements has important consequences for the three dimensional structure of proteins.

Generally, the two Cgroups are in a trans configuration, which minimizes steric interaction(cis/trans).

Modul 3. Proteins.

Primary structure of proteins. Secondary, tertiary and quaternary structures. Chemical properties and methods of definition of primary structure of proteins. Classification of proteins. The role of proteins in a food.

Peptides and Protein Primary Structure

Peptide bond formation: Note that a peptide bond is simply an amide bond between the alpha carboxyl and amino groups of amino acids. If we write the reacting groups in their unionized (acid and amine) forms, then we can see the reaction takes place with the loss of the elements of water, via an attack of the lone-pair electrons of the amine on the carbonyl carbon of the carboxyl group:

Now that we have looked at peptide bond formation, we next want to look at the structure of this bond and the sequence of amino acid residues (primary structures) of proteins. (Note that "residue" refers to the remainder of a molecule after it is incorporated into a polymer.)

The peptide bond is formed with the elimination of water, giving a planar bond between the carboxyl carbon and the amino nitrogen. [overhead 5.8 MvH] This is due to the partial double bond character on the amide/peptide bond as seen in the shorter bond length (0.133 nm vs. 0.146 nm). [overhead 7-2, V&V] This bond is nearly always trans in proteins due to steric interactions of the amide hydrogen and oxygen, except for proline.

Linear peptides will have free amino- and carboxy- terminal groups. Thus they will exhibit titration curves similar to a free amino acid, but with the pKavalues shifted closer to simple acid and amine values (there will be no charge stabilization).

By convention the amino terminal residue is written on the left progressing to the carboxyl terminal residue on the right:+H3N-aa-aa-aa-aa-CO2-.

Can determine the composition of a peptide by acid hydrolysis and amino acid analysis.

Can sequence proteins by specific enzyme and chemical hydrolysis to give peptides which can then be run through sequenators (up to about 100 aa's).

Amino acid sequences have been used to help determine relatedness of organisms.

3-D Structure of Proteins

Overview: Proteins are commonly large (MW > 6,000), globular molecules serving many functions.

Proteins are complex systems - difficult to understand at a fundamental structural level. Thus we search for patterns using normal perceptual tools: regularity, clustering, cleavage/separation/emptiness.

We are then able to discern alpha helices, beta sheets, beta turns, and "random" regions. 310helical regions show up with computer searches. None of these is necessarily more or less random than others, they are simply easier or more difficult for us to perceive as ordered. They exist through our rationalization. Often structural elements also appear to serve a functional role, thou this is through our dissection of the molecular machine.

Look at theoretical possibilities resulting from the available bond angles around the peptide bond system

Most peptide bonds are trans because of reduced steric hindrance. Most exceptions are with proline which has nearly equal hindrance in both cis and trans [overhead 5.8 P]

Any rotation in the peptide chain will therefore take place around the two bonds of the alpha carbon, referred to as the phi (f) and psi (y) bonds. There are a restricted number of angles which these bonds can achieve (Figure 4.8) [overhead 5.9 P, V&V 7.6]. Of course the range of angles will be further reduced due to side chains.

If we assume hard spherical atoms with van der Waals radii, we can determine the accessible phi (f) and psi (y) angles. This procedure was followed by Ramachandran to produce theRamachandran plot, an example is seen in Figure 4.9 of your text [overhead 6.2, MvH; 7.7 V&V].

There are only a few regions of possible angles available to the alpha carbon bonds as shown on this plot.

Note that the common secondary structures, the alpha helix, the beta strand, and the collagen triple helix all occur in these regions.

Of course real atoms are somewhat compressible and real bonds can bend a little, so we might wonder how this plot stacks up to reality. A study of the distribution of conformation angles of a thousand amino acid residues in eight proteins as determined by x-ray diffraction showed that most of the values do indeed fall in the predicted regions. Most of the residues outside of these regions are glycines, with the least restriction.

Let's go back and look at overall shape and interpret it. Look for substructures that recur in various molecules. Perhaps we see a globule is made of subglobules. Look closer and we see alpha helices and beta structures. Finally we can discern aa residues.

In order to understand and categorize their organization, protein structure has been divided into four hierarchical levels and a couple of sublevels:

Primary structure(1) : the linear order or sequence of peptide bonded amino acid residues, beginning at the N-terminus. (Characteristic bond type: covalent.)

Secondary structure(2): the steric relations of residues nearby in the primary structure which give rise to local regularities of conformation. These structures are maintained by hydrogen bonds between peptide bond carbonyl oxygens and amide hydrogens. The major secondary structural elements are the alpha helix and the beta strand. (Characteristic bond type: hydrogen.)

Tertiary structure(3): the steric relations of residues distant in the primary sequence; the overall folding pattern of a single covalently linked molecule. (Characteristic bond type: hydrophobic; others: hydrogen, ion-pair, van der Waals, disulfide.)

Super secondary structure(motifs): defined associations of secondary structural elements. (Characteristic bond type: hydrogen & hydrophobic.)

Domains: independent folding regions within a protein. The group/pattern of secondary structures forming a Domain's tertiary structure is called aFold. (Characteristic bond type: hydrophobic; others: hydrogen, ion-pair, van der Waals.)

Quarternary structure(4): the association of two or more independent proteins via non-covalent forces to give a multimeric protein. The individual peptide units of this protein are referred to as subunits, and they may be identical or different from one another. (Characteristic bond type: hydrophobic; others: hydrogen, ion-pair, van der Waals.)

3-D Structure of Proteins 2

Secondary Structure

Tertiary structure(3): the steric relations of residues distant in the primary sequence; the overall folding pattern of a single covalently linked molecule. (Characteristic bond type: hydrophobic; others: hydrogen, ion-pair, van der Waals, disulfide.)

Super secondary structure(motifs): defined associations of secondary structural elements. (Characteristic bond type: hydrogen & hydrophobic.)

Domains: independent folding regions within a protein. The group/pattern of secondary structures forming a Domain's tertiary structure is called aFold. (Characteristic bond type: hydrophobic; others: hydrogen, ion-pair, van der Waals.)

Last time looked at what is possible given the bond angles etc. between amino acid residues. Now can look at specific structures.

Alpha helix:(Figure 4.10, pg 90 of your text) [overhead 2.31 S, 5.15 P] The most frequent secondary structure is the right-handeda-helix.

In this cylinder-like structure the amino acid residues curl around in a spring/rod-like structure.

There is a rise/residue (movement along the axis) of 0.15 nm and a pitch (rise/turn) of 0.54 nm.

There are 3.6 residues per turn and 13 atoms/H-bonded "ring" - this makes it a 3.613helix.

Very importantly, the H-bonds are nearly linear and therefore of near maximum strength. The side chains of the helix stick out from the sides.

The stability of the helix is determined in part by the side chains. Thus glycine allows too much rotational freedom to favor this structure, while very large or like charged side chains can also destabilize it.

As you might expect a proline residue stops a helix abruptly since proline' s angles are not accommodated in the helix.

Beta Strand:(Figure 4.15, pg 93 of your text) [overhead 5.19 P] The next secondary structural element is the beta-strand, which is seen in the supersecondary structures called parallel and anti-parallel beta sheets [overheads 7.16 & 17 V&V].

The beta strand is in a sense an abstract structure, since, unlike thea-helix, a beta-strand does not exist alone, there is always another strand to make a sheet.

In the older literature beta-sheets are considered secondary structures, but they are more consistently considered super secondary with the current nomenclature.

Beta strands are nearly fully extended, thus they have very little extensibility (stretch).

Beta strands are stabilized by hydrogen bonding to adjacent beta-strands. Thus they are stabilized by inter-strand H-bonds whereasa-helices are stabilized by intra-strand H-bonds.

Aside: Fibrous proteins:alpha-keratin (hair etc., alpha-helix based) [overhead 7-11 V&V, 7-25 & 26]; stretched alpha-keratin (parallelb-pleated sheet) [overhead, Figure 7-26].

3-D Structure of Proteins 3

Secondary Structure, cont.

Collagen strand:This is a specialized structure occurring in only a particular family of fibrous proteins. It does not occur in globular proteins that I am aware of.

Collagen triple helix. Note repeating sequence of -(gly-x-y)- where x is usually proline and y is usually hydroxyproline. (Fig 4.36) [overheads: 11-8&10, S; 4-10 to 12]

Non-repetitive secondary elements:Proteins can also have non-repetitive secondary structures which consist of a few residues in a turn or loop. Among these are:

beta-turns:

Type I turns: Fig. 4.18, left [overhead 7.22, V&V] four amino acid residues in a 180 turn, usually H-bonded between the carbonyl O of the first residue and the amide N of the fourth. Proline is often the second residue. [overhead, 7-22 V&V]

Type II turns: Fig. 4.18 [overhead 7.22, V&V] four amino acid residues in a 180 turn, usually H-bonded between the carbonyl O of the first residue and the amide N of the fourth. Glycine is most frequently the third residue and proline is often the second residue. [overhead, 7-22 V&V]

A partial turn of a 310helix. Short sections of this helix often occur at the ends of alpha-helixes as transitional elements.

Tertiary Structures

TheTertiary structuredescribes the overall folding of a single covalent structure.

Lysozyme model [overhead, model]

As the number of known protein structures increased additional patterns became obvious within the tertiary level of structure: Motifs & Domains.

Super Secondary structures (Motifs)

Recall the two classical structures based on the beta-strand:

Anti-parallelb-pleated sheet: strong,linear H-bondsspaced adjacent, then R grp, then single, then R grp, then adjacent etc. (Fig 4.15b) [overhead 7-17 V&V, 5.19 P]

Parallelb-sheet: evenly spaced, butslanted H-bonds(less stable), (Fig 4.15a) [overhead 5.19 P]

Let's next look at some of the other more common motifs found in globular proteins (Fig 4.19 of your text):

Hairpin -b-strand-short loop-b-strand

b-meander - an anti-parallel beta sheet with short connecting loops

aamotif - two successive alpha-helixes with slightly inclined axis to give better contact between side chains

babunit: alternate pattern of beta-strands and alpha-helixes

Greek Key

b-sandwich

Domains

Large proteins (>200 aa's) usually fold up in smaller pieces of 100-200 aa's called domains. Recall that we define a Domain as an independent folding region in a protein. Often defined by clefts in 3D structure giving globular elements connected by "hinges" (single strand segments connecting the domains). Domains have the advantages of speeding up the folding process (fold domains independently, then assemble resultant folded domains - effectively processing folding of domains in parallel). Another advantage of domain structure is that nature can take bits of DNA specifying particular domains with particular functions and assemble them in new combinations to get new activities (e.g. combine an ATP binding site and a sugar binding site to give a sugar phosphorylating protein).

Example: IgG , domains, exons and evolution. [overheads: IgG/proteins; 7.23 MvH]

IgG made up of four independently synthesized proteins, 2 heavy chains with 4 domains each, and 2 light chains with 2 domains each.

Domain types:b-meander [anti-parallelb-sheet],b-barrel. (Note that Motifs and Domains often use the same nomenclature, and indeed often overlap. Can in fact have Motif = Domain = Tertiary structure!)

Domains correspond to exons of DNA (frequently, but not always the case)

The domains are all apparently related through gene duplication in the remote past.

The active site of IgG (2/IgG) is made up between two domains, one from a heavy chain and one from a light chain.

When immune system is developing individual cells express single IgG molecules made from randomly expressed heavy and light chains.

In a similar manner we see that many enzymes have active sites created between two domains, often one domain binds one substrate while the second binds a second substrate.

Its as if these proteins were designed by taking "off-the-shelf" components, assembling them, and then over time (and generations) tuning the combination up.

3-D Structure of Proteins 4

Domains, cont.

Note that domains will have their own tertiary structures, made up of secondary and frequently supersecondary elements. Domains can be categorized into four main groups:

1. All alpha

2. All beta

3. alpha/beta (have alternating alpha and beta structures, such as in the beta-alpha-beta motif)

4. alpha + beta (local clusters of alpha and beta in same chain with each cluster consisting of contiguous primary structure).

Groups of motifs forming the core of the tertiary structures of domains are referred to asFolds. (p 99) Over 600 folds have been discovered, with an expectation that about 1,000 exist. (a bunch, but well below the infinite number possible!) Common examples include (Fig 4.24) [overhead]:

Parallel twisted sheet.

Beta barrel.

Alpha/Beta barrel.

Parallel twisted sheet .

Folds/Motifs are often more highly conserved than sequences, and so are used along with sequences to trace relatedness among molecules and thus organisms. An example of conservation for a domain is seen in Cytochrome c as shown in your text in Figure 4.21.

Quaternary Protein Structure

ternary (4) structures(Fig. 4.25; overheads: MvH 6.26, Fig 25): Geometrically specific associations of protein subunits; the spatial arrangement of protein subunits.

Folding Hierarchy Overview

Rationale for quaternary:There are a variety of advantages to large structures:

Increasing the size of a protein allows better "fits" for catalysis and binding - many weak bonds are needed to maintain specific structures.

Can bring sequential active sites of metabolic pathways into close proximity.

However, large peptides have some problems:

The process of folding slows tremendously with increasing size, thus folding individual subunits, and assembling these subunits can greatly enhance folding efficiency.

Get about 1 error / 103aa residues due to the precision of the translation of messenger RNA to protein. Thus need to keep residue number down.

Interacting subunits provide mechanisms for regulation.

Quaternary structures allows the assembly of large to extremely large structures.

Protein Folding

Primary structure specifies tertiary (& therefore quaternary) structure. This is known fromin vitrodenaturation/renaturationstudies of small proteins.

Denaturationmeans to unfold to non-functional state, often achieve a "random coil" in solution,

Renaturationmeans to return to the properly folded, natural, and functional state.)

The classic study involved Ribonuclease: Reduce (break) -S-S- bonds, denature with urea to random coil. Now can renature by gently removing denaturant (urea) and oxidize -S-S- bonds. [overhead 5.41, P] Enzyme activity fully recovered. X-ray diffraction image same! Note - no gremlins, no magic, done in "test tube."

Other small proteins, such as Myoglobin and proinsulin, fold up spontaneously in the same manner as Ribonuclease. However, insulin fails to fold correctly, since a peptide essential to folding has been cleaved off.

Accesory Folding Proteins.The ribonuclease renaturation-type experiment has not been repeated with large proteins, which seem to require the participation of "folding catalysts," the chaperones, to aid their folding.

Modul 4. Enzymes.

The nomenclature and classification of ferments. Frame and catalytic properties of ferments. Temperature effect, , concentration of ferment and substrate for speed of enzymatic reactions. Regulation of activity of ferments

Enzymes are found all around us, they are found in every plant and animal. Any living organismneeds enzymes for its functioning. All living beingare controlled by chemical reactions. Chemical reactions that are involved ingrowth, blood coagulation,healing, combating disease,breathing, digestion,reproduction, and everything elseare catalyzed by enzymes. Our body contains about 3,000 enzymes that are constantly regenerating, repairing and protecting us.

Enzymes are powerhouses that are able to perform variety of functions in the human body. Enzymes are wondrous chemicals of nature. Enzymes are used in supplement form in medical arena. Although our bodies can make most of the enzymes, our body can wreak havoc the body's enzyme system and cause enzyme depletiondue to poor diet, illness, injury and genetics.

Enzymes Definition

Enzymes are large biomolecules that are responsible for many chemical reactions that are necessary to sustain life. Enzyme is a protein molecule and are biological catalysts. Enzymes increase the rate of the reaction. Enzymes are specific, they function with only one reactant to produce specific products. Enzymes have a three-dimensional structure and they utilize organic molecules like biotinand inorganic molecules like metal ions (magnesium ions) for assistance in catalysis.

Substrate is the reactant in an enzyme catalyzed reaction. The portion of the molecule that is responsible for catalytic action of enzyme is the active site.

Characteristics of Enzymes

Characteristics of enzymes are as follows:

Enzymes possess great catalytic power.

Enzymes are highy specific.

Enzymes show varying degree of specificities.

Absolute specificity where the enzymes react specifically with only one substrate.

Stereo specificity is where the enzymes can detect the different optical isomers and react to only one type of isomer.

Reaction specific enzymes, these enzymes as the name suggests reacts to specific reactions only.

Group specific enzymes are those that catalyze a group of substances that contain specific substances.

The enzyme activity can be controlled but the activity of the catalysts can not be controlled.

All enzymes are proteins.

Like the proteins, enzymes can be coagulated by alcohol, heat, concentrated acids and alkaline reagents.

At higher temperatures the rate of the reaction is faster.

The rate of the reaction invovlving an enzyme is high at the optimum temperature.

Enzymes have an optimum pH range within which the enzymes function is at its peak.

If the substrate shows deviations larger than the optimum temperature or pH, required by the enzyme to work, the enzymes do not function such conditions.

Increase in the concentration of the reactants, and substrate the rate of the reaction increase until the enzyme will become saturated with the substrate; increase in the amount of enzyme, increases the rate of the reaction.

Inorganic substances known as activators increase the activity of the enzyme.

Inhibitors are substances that decrease the activity of the enzyme or inactivate it.

Competitive inhibitors are substances that reversibly bind to the active site of the enzyme, hence blocking the substrate from binding to the enzyme.

Incompetitive inhibitors are substances that bind to any site of the enzyme other than the active site, making the enzyme less active or inactive.

Irreversible inhibitors are substances that from bonds with enzymes making them inactive.

Enzyme Classification

The current system of nomenclature of enzymes uses the name of the substrate or the type of the reaction involved, and ends with "-ase". Example:'Maltase'- substrate is maltose.'Hydrolases'- reaction type is hydrolysisreaction.

Classification of enzymes

Enzymes areclassified based on the reactions they catalyze into 6 groups:Oxidoreductases, transferases, hydrolases, lyases, isomearses, ligases.

Oxidoreductases -Oxidoreductase are the enzymes that catalyze oxidation-reduction reactions. These emzymes are important as these reactions are responsible for the production of heat and energy.

Transferases -Transferases are the enzymes that catalyze reactions where transfer of functional group between two substrates takes place.

Hydrolases -Hydrolases are also known as hydrolytic enzymes, they catalyze the hydrolysis reactions of carbohydrates, proteins and esters.

Lyases - Lyases are enzymes that catlayze the reaction invvolving the removal of groups from substrates by processes other than hydrolysis by the formation of double bonds.

Isomerases - Isomerases are enzymes that catalyze the reactions where interconversion of cis-trans isomers is involved.

Ligases -Ligases are also known as synthases, these are the enzymes that catalyze the reactions where coupling of two compounds is involved with the breaking of pyrophosphate bonds.

Structure of Enzymes

Enzymes are proteins, like the proteins the enzymes contain chains of amino acids linked together. The characteristic of an enzyme is determined by the sequence of amino acid arrangement.When the bonds between the amino acid are weak, they may be broken by conditions of high temperatures or high levels of acids. When these bonds are broken, the enzymes become nonfunctional. The enzymes that take part in the chemical reaction do not undergo permanent changes and hence they remain unchanged to the end of the reaction.

Enzymes are highly selective, they catalyze specific reactions only.Enzymes have a part of a molecule where it just has the shape where only certain kind of substrate can bind to it, this site of activity is known as the 'active site'.The molecules that react and bind to the enzyme is known as the 'substrate'.

Most of the enzymes consists of the protein and the non protein part called the 'cofactor'. The proteins in the enzymes are usually globular proteins. The protein part of the enzymes areknown 'apoenzyme', whilethe non-protein part is known as the cofactor.Together the apoenzyme and cofactors are known as the 'holoenzyme'.

Cofactors may be of three types: prosthetic groups, activators and coenzymes.

Prosthetic groups are organic groups that are permanently bound to the enzyme.Example: Heme groups of cytochromes and bitotin group of acetyl-CoA carboxylase.

Activators are cations- they are positively charged metal ions. Example: Fe - cytochrome oxidase,CU - catalase,Zn - alcohol dehydrogenase, Mg - glucose - 6 - phosphate, etc.

Coenzymes are organic molecules, usually vitamins or made from vitamins. they are not bound permanently to theenzyme, but they combine with the enzyme-substrate complex temporarily. Example:FAD - Flavin Adenine Dinucleotide, FMN - Flavin Mono Nucleotide, NAD - Nicotinamide Adenine Dinucleotide, NADP - Nicotinamide Adenine Dinucleotide.

Functionof Enzymes

Biological Functions of Enzymes:

Enzymes perform a wide variety of functions in living organisms.

They are major components in signal transduction and cell regulation, kinases and phosphatases help in this function.

They take part in movement with the help of the protein myosin which aids in muscle contraction.

Also other ATPases in the cell membrane acts as ion pumps in active transport mechanism.

Enzymes present in the viruses are for infecting cell.

Enzymes play a important role in the digestive activity of the enzymes.

Amylases and proteases are enzyme sthat breakdown large molecules into absorbable molecules.

Variuos enzymes owrk together in a order forming metabolic pathways. Example: Glycolysis.

Industrial Application of Enzymes:

Food Processing - Amylases enzymes from fungi and plants are used in production of sugars from starch inmaking corn-syrup.

Catalyze enzyme is used in breakdown of starch into sugar, and in baking fermentation process of yeast raises the dough.

Proteases enzyme help in manufacture of biscuits in lowering the protein level.

Baby foods - Trypsin enzyme is used in pre-digestion of baby foods.

Brewing industry - Enzymes from barley are widely used in brewing industries.

Amylases, glucanases, proteases, betaglucanases, arabinoxylases, amyloglucosidase, acetolactatedecarboxylases are used in prodcution of beer industries.

Fruit juices - Enzymes like cellulases,pectinases help are used in clarifying fruit juices.

Dairy Industry - Renin is used inmanufacture of cheese. Lipases are used in ripening blue-mold cheese. Lactases breaks down lactose to glucose and galactose.

Meat Tenderizes - Papain is used to soften meat.

Starch Industry - Amylases, amyloglucosidases and glycoamylases converts starch into glucose and syrups.

Glucose isomerases - production enhanced sweetening properties and lowering calorific values.

Paper industry - Enzymes like amylases, xylanases, cellulases and liginases lower the viscosity, and removes lignin to soften paper.

Biofuel Industry - Enzymes like cellulases are used in breakdown of cellulose into sugars which can be fermented.

Biological detergent - proteases, amylases, lipases, cellulases, asist in removal of protein stains, oily stains and acts as fabric conditioners.

Rubber Industry - Catalase enzyme converts latex into foam rubber.

Molecular Biology - Restriction enzymes, DNA ligase and polymerases are used in genetic engineering, pharmacology, agriculture, medicine, PCR techniques, and are also important in forensic science.

Examples of Enzymes

A few well known examples of enzymes are as follows: Lipases, Amylases, Maltases, Pepsin, Protease, Catalases, Maltase, Sucrase, Pepsin, Renin, Catalases,

A few examples of foods that are rich in enzymes:

Enzymes are available in the food we eat. Foods that are canned, or processed food like irradiation,drying, and freezing make the foods enzyme dead. Refined foods are void of any sort of nutrition. Food that is whole, uncooked and unpasteurized milk will provide enough enzymes. There are two basic ways to increase enzyme intake. First is to eat more fresh foods, cooking tends to kill enzymes. Raw fruits and vegetables are a good source of enzymes. Fermented food like yoghurt, intake improves body's enzyme status. The other way to increase enzyme status of the body is by intake of enzyme supplements.

Here is a list of foods rich in enzymes - Apples, apricots, asparagus, avocado, banana, beans, beets, broccoli, cabbage, carrots, celery, cherries, cucumber, figs, garlic, ginger, grapes, green barley grass,kiwi fruit, etc.

Modul 5. Vitamins

The definition, constitution and classification of vitamins and their role in enzymatic reactions and in exchange processes.

Vitamins are natural substances found in plants and animals and known as Essential nutrients for human beings. The name vitamin is obtained from "vital amines" as it was originally thought that these substances were all amines. Human body uses these substances to stay healthy and support its many functions. There are two types of vitamins: water-soluble and fat-soluble.The body needs vitamins to stay healthy and a varied diet usually gives you all the vitamins you need. Vitamins do not provide energy (calories) directly, but they do help regulate energy-producing processes. With the exception of vitamin D and K, vitamins cannot be synthesized by the human body and must be obtained from the diet. Vitamins have to come from food because they are not manufactured or formed by the body.

There are several roles for vitamins and trace minerals in diseases:

Deficiencies of vitamins and minerals may be caused by disease states such as mal absorption;

Deficiency and excess of vitamins and minerals can cause disease in and of themselves (e.g., vitamin A intoxication and liver disease);

Vitamins and minerals in high doses may be used as drugs (e.g., niacin for hypercholesterolemia).

Vitamins are essential for the normal growth and development of a multi-cellular organism. The developing fetus requires certain vitamins and minerals to be present at certain times. If there is serious deficiency in one or more of these nutrients, a child may develop a deficiency disease. Deficiencies of vitamins are classified as either primary or secondary.

Primary Deficiency:A primary deficiency occurs when you do not get enough of the vitamin in the food you eat.

Secondary Deficiency:A secondary deficiency may be due to an underlying disorder that prevents or limits the absorption or use of the vitamin.

Types of Vitamins

Vitamins, one of the most essential nutrients required by the body and can be broadly classified into two main categories i.e., water-soluble vitamins and fat-soluble vitamins.

Water-Soluble VitaminsB-complex Vitamins

Eight of the water-soluble vitamins are known as the vitamin B-complex group: thiamin (vitamin B1), riboflavin (vitamin B2), niacin (vitamin B3), vitamin B6 (pyridoxine), folate (folic acid), vitamin B12, biotin and pantothenic acid. The B vitamins are widely distributed in foods,and their influence is felt in many parts of the body. They function as coenzymes that help the body obtain energy from food. The B vitamins are also important for normal appetite, good vision, and healthy skin, nervous system, and red blood cell formation.

Thiamin: Vitamin B1

What is Thiamin. Thiamin, or vitamin B1, helps to release energy from foods, promotes normal appetite, and is important in maintaining proper nervous system function.

Food Sources for Thiamin. Sources include peas, pork, liver, and legumes. Most commonly, thiamin is found in whole grains and fortified grain products such as cereal, and enriched products like bread, pasta, rice, and tortillas. The process of enrichment adds back nutrients that are lost when grains are processed. Among the nutrients added during the enrichment process are thiamin (B1), niacin (B3), riboflavin (B2), folate and iron.

Thiamin Deficiency. Under-consumption of thiamin is rare in the United States due to wide availability of enriched grain products. However, low calorie diets as well as diets high in refined and processed carbohydrates may place one at risk for thiamin deficiency. Alcoholics are especially prone to thiamin deficiency because excess alcohol consumption often replaces food or meals. Symptoms of thiamin deficiency include: mental confusion, muscle weakness, wasting, water retention (edema), impaired growth, and the disease known as beriberi. Thiamin deficiency is currently not a problem in the United States.

Too much Thiamin. No problems with overconsumption are known for thiamin.

Riboflavin: Vitamin B2

What is Riboflavin. Riboflavin, or vitamin B2, helps to release energy from foods, promotes good vision, and healthy skin. It also helps to convert the amino acid tryptophan (which makes up protein) into niacin.

Food Sources for Riboflavin. Sources include liver, eggs, dark green vegetables, legumes, whole and enriched grain products, and milk. Ultraviolet light is known to destroy riboflavin, which is why most milk is packaged in opaque containers instead of clear.

Riboflavin Deficiency. Under consumption of riboflavin is rare in the United States. However, it has been known to occur with alcoholism, malignancy, hyperthyroidism, and in the elderly. Symptoms of deficiency include cracks at the corners of the mouth, dermatitis on nose and lips, light sensitivity, cataracts, and a sore, red tongue.

Too much Riboflavin. No problems with overconsumption are known for riboflavin.

Niacin: Vitamin B3, Nicotinamide, Nicotinic Acid.

What is Niacin. Niacin, or vitamin B3, is involved in energy production, normal enzyme function, digestion, promoting normal appetite, healthy skin, and nerves.

Food Sources for Niacin. Sources include liver, fish, poultry, meat, peanuts, whole and enriched grain products.

Niacin Deficiency. Niacin deficiency is not a problem in the United States. However, it is known to occur with alcoholism, protein malnourishment, low calorie diets, and diets high in refined carbohydrates. Pellagra is the disease state that occurs as a result of severe niacin deficiency. Symptoms include cramps, nausea, mental confusion, and skin problems.

Too much Niacin. Consuming large doses of niacin supplements may cause flushed skin, rashes, or liver damage. Over consumption of niacin is not a problem if it is obtained through food.

Vitamin B6: Pyridoxine, Pyridoxal, Pyridoxamine

What is Vitamin B6. Vitamin B6, otherwise known as pyridoxine, pyridoxal or pyridoxamine, aids in protein metabolism and red blood cell formation. It is also involved in the bodys production of chemicals such as insulin and hemoglobin.

Food Sources for Vitamin B6. Sources include pork, meats, whole grains and cereals, legumes, and green, leafy vegetables.

Vitamin B6 Deficiency.Deficiency symptoms include skin disorders, dermatitis, cracks at corners of mouth, anemia, kidney stones, and nausea. A vitamin B6 deficiency in infants can cause mental confusion.

Too much Vitamin B6. Over consumption is rare, but excess doses of vitamin B6 over time have been known to result in nerve damage.

Folate: Folic Acid, Folacin

What is Folate. Folate, also known as folic acid or folacin, aids in protein metabolism, promoting red blood cell formation, and lowering the risk for neural tube birth defects. Folate may also play a role in controlling homocysteine levels, thus reducing the risk for coronary heart disease.

Food Sources for Folate. Sources of folate include liver, kidney, dark green leafy vegetables, meats, fish, whole grains, fortified grains and cereals, legumes, and citrus fruits. Not all whole grain products are fortified with folate. Check the nutrition label to see if folic acid has been added.

Folate Deficiency. Folate deficiency affects cell growth and protein production, which can lead to overall impaired growth. Deficiency symptoms also include anemia and diarrhea. A folate deficiency in women who are pregnant or of child bearing age may result in the delivery of a baby with neural tube defects such as spina bifida.

Too much Folate. Over consumption of folate offers no known benefits, and may mask B12 deficiency as well as interfere with some medications.

Vitamin B12: Cobalamin

What is B12. Vitamin B12, also known as cobalamin, aids in the building of genetic material, production of normal red blood cells, and maintenance of the nervous system.

Food Sources for Vitamin B12. Vitamin B12 can only be found only in foods of animal origin such as meats, liver, kidney, fish, eggs, milk and milk products, oysters, shellfish. Some fortified foods may contain vitamin B12.

Vitamin B12 Deficiency. Vitamin B12 deficiency most commonly affects strict vegetarians (those who eat no animal products), infants of vegan mothers, and the elderly. Symptoms of deficiency include anemia, fatigue, neurological disorders, and degeneration of nerves resulting in numbness and tingling. In order to prevent vitamin B12 deficiency, a dietary supplement should be taken. Some people develop a B12 deficiency because they cannot absorb the vitamin through their stomach lining. This can be treated through vitamin B12 injections.

Too much Vitamin B12. No problems with overconsumption of vitamin B12 are known.

Biotin

What is Biotin. Biotin helps release energy from carbohydrates and aids in the metabolism of fats, proteins and carbohydrates from food.

Food Sources for Biotin. Sources of Biotin include liver, kidney, egg yolk, milk, most fresh vegetables, yeast breads and cereals. Biotin is also made by intestinal bacteria.

Biotin Deficiency. Biotin deficiency is uncommon under normal circumstances, but symptoms include fatigue, loss of appetite, nausea, vomiting, depression, muscle pains, heart abnormalities and anemia.

Too much Biotin. No problems with overconsumption are known for Biotin.

Pantothenic Acid

What is Pantothenic Acid. Pantothenic Acid is involved in energy production, and aids in the formation of hormones and the metabolism of fats, proteins, and carbohydrates from food.

Food Sources for Pantothenic Acid. Sources include liver, kidney, meats, egg yolk, whole grains, and legumes. Pantothenic Acid is also made by intestinal bacteria.

Pantothenic Acid Deficiency. Pantothenic Acid deficiency is uncommon due to its wide availability in most foods.

Too much Pantothenic Acid. No problems with overconsumption are known for Pantothenic Acid. Rarely, diarrhea and water retention will occur with excessive amounts.

Vitamin C: Ascorbic Acid, AscorbateWhat is Vitamin C

The body needs vitamin C, also known as ascorbic acid or ascorbate, to remain in proper working condition. Vitamin C benefits the body by holding cells together through collagen synthesis; collagen is a connective tissue that holds muscles, bones, and other tissues together. Vitamin C also aids in wound healing, bone and tooth formation, strengthening blood vessel walls, improving immune system function, increasing absorption and utilization of iron, and acting as an antioxidant.

Since our bodies cannot produce or store vitamin C, an adequate daily intake of this nutrient is essential for optimum health. Vitamin C works with vitamin E as an antioxidant, and plays a crucial role in neutralizing free radicals throughout the body. An antioxidant can be a vitamin, mineral, or a carotenoid, present in foods, that slows the oxidation process and acts to repair damage to cells of the body. Studies suggest that vitamin C may reduce the risk of certain cancers, heart disease, and cataracts. Research continues to document the degree of these effects.

Food Sources for Vitamin C. Consuming vitamin C-rich foods is the best method to ensure an adequate intake of this vitamin. While many common plant foods contain vitamin C, the best sources are citrus fruits. For example, one orange, a kiwi fruit, 6 oz. of grapefruit juice or 1/3 cup of chopped sweet red pepper each supply enough vitamin C for one day.

Vitamin C Deficiency. Although rare in the United States, severe vitamin C deficiency may result in the disease known as scurvy, causing a loss of collagen strength throughout the body. Loss of collagen results in loose teeth, bleeding and swollen gums, and improper wound healing. More commonly, vitamin C deficiency presents as a secondary deficiency in alcoholics, the elderly, and in smokers.

The following conditions have been shown to increase vitamin C requirements (Table 1):

Environmental stress, such as air and noise pollution

Use of certain drugs, such as oral contraceptives

Tissue healing of wounds

Growth (children from 0- 12 months, and pregnant women)

Fever and infection

Smoking.

Too Much Vitamin C. Despite being a water-soluble vitamin that the body excretes when in excess, vitamin C overdoses have been shown to cause kidney stones, gout, diarrhea, and rebound scurvy.

Fat-Soluble Vitamins

The fat-soluble vitamins, A, D, E, and K, are stored in the body for long periods of time and generally pose a greater risk for toxicity when consumed in excess than water-soluble vitamins. Eating a normal, well-balanced diet will not lead to toxicity in otherwise healthy individuals. However, taking vitamin supplements that contain megadoses of vitamins A, D, E and K may lead to toxicity. The body only needs small amounts of any vitamin.

While diseases caused by a lack of fat-soluble vitamins are rare in the United States, symptoms of mild deficiency can develop without adequate amounts of vitamins in the diet. Additionally, some health problems may decrease the absorption of fat, and in turn, decrease the absorption of vitamins A, D, E and K. Consult a medical professional about any potential health problems that may interfere with vitamin absorption.

Vitamin A: RetinolWhat is Vitamin A

Vitamin A, also called retinol, has many functions in the body. In addition to helping the eyes adjust to light changes, vitamin A plays an important role in bone growth, tooth development, reproduction, cell division, gene expression, and regulation of the immune system. The skin, eyes, and mucous membranes of the mouth, nose, throat and lungs depend on vitamin A to remain moist. Vitamin A is also an important antioxidant that may play a role in the prevention of certain cancers.

Food Sources for Vitamin A

Eating a wide variety of foods is the best way to ensure that the body gets enough vitamin A. The retinol, retinal, and retinoic acid forms of vitamin A are supplied primarily by foods of animal origin such as dairy products, fish and liver. Some foods of plant origin contain the antioxidant, betacarotene, which the body converts to vitamin A. Beta-carotene, comes from fruits and vegetables, especially those that are orange or dark green in color. Vitamin A sources also include carrots, pumpkin, winter squash, dark green leafy vegetables and apricots, all of which are rich in beta-carotene.

Compared to vitamin A, it takes twice the amount of carotene rich foods to meet the bodys vitamin A requirements, so one may need to increase consumption of carotene containing plant foods.

Recent studies indicate that vitamin A requirements may be increased due to hyperthyroidism, fever, infection, cold, and exposure to excessive amounts of sunlight. Those that consume excess alcohol or have renal disease should also increase intake of vitamin A.

Vitamin A Deficiency

Vitamin A deficiency in the United States is rare, but the disease that results is known as xerophthalmia. It most commonly occurs in developing nations usually due to malnutrition. Since vitamin A is stored in the liver, it may take up to 2 years for signs of deficiency to appear. Night blindness and very dry, rough skin may indicate a lack of vitamin A. Other signs of possible vitamin A deficiency include decreased resistance to infections, faulty tooth development, and slower bone growth.

Too much Vitamin A

In the United States, toxic or excess levels of vitamin A are more of a concern than deficiencies. The Tolerable Upper Intake Level (UL) for adults is 3,000 mcg RAE (Table 2). It would be difficult to reach this level consuming food alone, but some multivitamin supplements contain high doses of vitamin A. If you take a multivitamin, check the label to be sure the majority of vitamin A provided is in the form of beta-carotene, which appears to be safe. Symptoms of vitamin A toxicity include dry, itchy skin, headache, nausea, and loss of appetite. Signs of severe overuse over a short period of time include dizziness, blurred vision and slowed growth. Vitamin A toxicity also can cause severe birth defects and may increase the risk for hip fractures.

Vitamin DWhat is Vitamin D

Vitamin D plays a critical role in the bodys use of calcium and phosphorous. It works by increasing the amount of calcium absorbed from the small intestine, helping to form and maintain bones. Vitamin D benefits the body by playing a role in immunity and controlling cell growth. Children especially need adequate amounts of vitamin D to develop strong bones and healthy teeth.

Food Sources for Vitamin D

The primary food sources of vitamin D are milk and other dairy products fortified with vitamin D. Vitamin D is also found in oily fish (e.g., herring, salmon and sardines) as well as in cod liver oil. In addition to the vitamin D provided by food, we obtain vitamin D through our skin which produces vitamin D in response to sunlight.

Vitamin D Deficiency

Symptoms of vitamin D deficiency in growing children include rickets (long, soft bowed legs) and flattening of the back of the skull. Vitamin D deficiency in adults may result in osteomalacia (muscle and bone weakness), and osteoporosis (loss of bone mass).

Recently published data introduces a concern that some adults and children may be more prone to developing vitamin D deficiency due to an increase in sunscreen use. In addition, those that live in inner cities, wear clothing that covers most of the skin, or live in northern climates where little sun is seen in the winter are also prone to vitamin D deficiency. Since most foods have very low vitamin D levels (unless they are enriched) a deficiency may be more likely to develop without adequate exposure to sunlight. Adding fortified foods to the diet such as milk, and for adults including a supplement, are effective at ensuring adequate vitamin D intake and preventing low vitamin D levels.

Vitamin D deficiency has been associated with increased risk of common cancers, autoimmune diseases, hypertension, and infectious disease. In the absence of adequate sun exposure, at least 800 to 1,000 IU of vitamin D3 may be needed to reach the circulating level required to maximize vitamin Ds benefits.

Who is at Risk These populations may require extra vitamin D in the form of supplements or fortified foods:

Exclusively breast-fed infants: Human milk only provides 25 IU of vitamin D per liter. All breast-fed and partially breast-fed infants should be given a vitamin D supplement of 400 IU/day

Dark Skin: Those with dark pigmented skin synthesize less vitamin D upon exposure to sunlight compared to those with light pigmented skin.

Elderly: This population has a reduced ability to synthesize vitamin D upon exposure to sunlight, and is also more likely to stay indoors and wear sunscreen which blocks vitamin D synthesis.

Covered and protected skin: Those that cover all of their skin with clothing while outside, and those that wear sunscreen with an SPF factor of 8, block most of the synthesis of vitamin D from sunlight.

Disease: Fat malabsorption syndromes, inflammatory bowel disease (IBD), and obesity are all known to result in a decreased ability to absorb and/or use vitamin D in fat stores.

Vitamin E: Tocopherol

Vitamin E benefits the body by acting as an antioxidant, and protecting vitamins A and C, red blood cells, and essential fatty acids from destruction. Research from decades ago suggested that taking antioxidant supplements, vitamin E in particular, might help prevent heart disease and cancer. However, newer findings indicate that people who take antioxidant and vitamin E supplements are not better protected against heart disease and cancer than non-supplement users. Many studies show a link between regularly eating an antioxidant rich diet full of fruits and vegetables, and a lower risk for heart disease, cancer, and several other diseases. Essentially, recent research indicates that to receive the full benefits of antioxidants and phytonutrients in the diet, one should consume these compounds in the form of fruits and vegetables, not as supplements.

Food Sources for Vitamin E

About 60 percent of vitamin E in the diet comes from vegetable oil (soybean, corn, cottonseed, and safflower). This also includes products made with vegetable oil (margarine and salad dressing). Vitamin E sources also include fruits and vegetables, grains, nuts (almonds and hazelnuts), seeds (sunflower) and fortified cereals.

Vitamin E Deficiency

Vitamin E deficiency is rare. Cases of vitamin E deficiency usually only occur in premature infants and in those unable to absorb fats. Since vegetable oils are good sources of vitamin E, people who excessively reduce their total dietary fat may not get enough vitamin E.

Too much Vitamin E

The Tolerable Upper Intake Level (UL) for vitamin E is shown in Table 2. Vitamin E obtained from food usually does not pose a risk for toxicity. Supplemental vitamin E is not recommended due to lack of evidence supporting any added health benefits. Megadoses of supplemental vitamin E may pose a hazard to people taking blood-thinning medications such as Coumadin (also known as warfarin) and those on statin drugs.

Vitamin KWhat is Vitamin K

Vitamin K is naturally produced by the bacteria in the intestines, and plays an essential role in normal blood clotting, promoting bone health, and helping to produce proteins for blood, bones, and kidneys.

Food Sources for Vitamin K

Good food sources of vitamin K are green, leafy-vegetables such as turnip greens, spinach, cauliflower, cabbage and broccoli, and certain vegetables oils including soybean oil, cottonseed oil, canola oil and olive oil. Animal foods, in general, contain limited amounts of vitamin K.

Vitamin K Deficiency

Without sufficient amounts of vitamin K, hemorrhaging can occur. Vitamin K deficiency may appear in infants or in people who take anticoagulants, such as Coumadin (warfarin), or antibiotic drugs. Newborn babies lack the intestinal bacteria to produce vitamin K and need a supplement for the first week. Those on anticoagulant drugs (blood thinners) may become vitamin K deficient, but should not change their vitamin K intake without consulting a physician. People taking antibiotics may lack vitamin K temporarily because intestinal bacteria are sometimes killed as a result of long-term use of antibiotics. Also, people with chronic diarrhea may have problems absorbing sufficient amounts of vitamin K through the intestine and should consult their physician to determine if supplementation is necessary.

Too much Vitamin K

Although no Tolerable Upper Intake Level (UL) has been established for vitamin K, excessive amounts can cause the breakdown of red blood cells and liver damage. People taking blood-thinning drugs or anticoagulants should moderate their intake of foods with vitamin K, because excess vitamin K can alter blood clotting times. Large doses of vitamin K are not advised.

Modul 6.Carbohydrates

Classification of carbohydrates and their most important reactions. Disaccharides and polysaccharides: lactose, maltose, sucrose, starch, glycogen, cellulose, quinine. The role of carbohydrates in a food.

CARBOHYDRATES

The carbohydrates, or sugars, are our third group of biomolecules. They are characterized by having a carbonyl carbon (aldehyde or ketone) and multiple hydroxyl groups. The smallest sugars are thus the three carbontrioses, glyceraldehyde (aldotriose) and dihydroxyacetone (ketotriose).

Note that sugars occur in both D and L forms. As we shall see the natural sugars are generally D.

CARBOHYDRATES, cont.

Note that sugars occur in both D and L forms. As we shall see the natural sugars are generally D. Let's look at the two families, aldoses and ketoses. The important aldoses (Figure 8.3, p 234) [overhead 9.4 P] include the five carbonaldopentose, ribose:

which commonly occurs in the cyclicfuranoseform.The six carbonaldohexoses, glucose, mannose, and galactose.

which commonly occur in the cyclicpyranoseform (as shown for glucose) [glucose model], and the six carbonketohexose, fructose.

which commonly occurs in a cyclicfuranoseform. The important ketoses include dihydroxyacetone, D-Xylulose, D-Ribulose, and D-Fructose [overhead 9.7 P]Note the relationship between the Fischer projections and the cyclic Haworth projections, using the example of glucose.

The ring is then sealed via a hemiacetal bond. [overhead 9.10 P] This would normally be quite unstable, however the closeness of the two reacting centers in the same chain makes them poor leaving groups, thus the hemiacetal is in fact the stable form of the six carbon aldoses. Thus the expected aldehyde chemistry for glucose is not seen (glucose is stable to oxygen etc.).Note that if drawn in the proper conformations (Figure 8.11, p 239), or if constructed as models it will be seen that the chair conformation should be more stable. In addition, the beta configuration of the hemiacetal -OH will be equatorial and should thus be preferred steriochemically as is in fact the case. Interestingly organisms can generally only use the alpha form, so isomerases are provide to interchange the two.

An important reaction is the Lobry-de-Bruyn-van Ekenstein Transformation. This base catalyzed reaction sequence interconverts three of the major hexoses, and will be used later in understanding some isomerase enzyme mechanisms. The mechanism is symmetrical. You should finish the second half on your own.

DISACCHARIDES

Can link sugars via acetal bonds, known as glycosidic bonds.

There are four common disaccharides (Fig 8.20, p 244) [overhead 9.24, P]:

maltose [-D-Glucopyranosyl-(1,4)--D-glucopyranose]

cellobiose [-D-Glucopyranosyl-(1,4)--D-glucopyranose]

lactose [beta-D-Galactopyranosyl-(1,4)-beta-D-glucopyranose], and

sucrose [alpha-D-Glucopyranosyl-(1,2)-beta-D-fructofuranoside]

The first three are reducing sugars, that is they have "free" aldehyde groups, whereas sucrose has both carbonyl groups tied up in the relatively stable g