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Chapter 4: Chemical Composition of Cells

y Organics compound are large macromolecules that contains Carbon and HydrogenImportance of water

1) SupportMajor component of protoplasm Provide support to non-woody plants (turgor pressure)

2) Moisten surface moisture gaseous exchange structure to facilitate respiratory gas diffusion3) Universal solventmedium of biochemical reaction and transport medium in organisms4) Lubricantmain components of mucin which lubricates movement of food in digestive

tracts

5) Maintain body temperature water has high heat capacity which can buffer organismsagainst rapid temperature changes

Carbohydrates

1) Contain elements: Carbon, Hydrogen, Oxygen2) General formula: (CH2O)n3) The main classes ofCarbohydrates

a. Monosaccharides :i. Monomers ofCarbohydrates

ii. Example : Glucose, Fructose, Galactoseb. Disaccharides :

i. Formed by condensation of two monosaccharides with removal of amolecule of water

ii. Two monosaccharides units are bond via the formation of glycosidic bond.iii. Example: Maltose, Sucrose, Lactose

iv. All monosaccharide and disaccharides (except for sucrose) are reducingsugar.

v. Test for reducing sugar: Blue color of Benedicts reagent or Fehlingsolution will turn brick-red precipitate in presence of reducing sugar.

c. Polysaccharides:i. Polymer synthesized from the condensation of monosaccharides by

process of polymerization

ii. Examples: Starch, Glycogen, Cellulose, Chitin4) Function:

a. Provide energy in form of glucose. Energy is stored in form of Starch inplants and glycogen in animals

b. Structural components in cells. For example, cellulose is found in plants;and chitin is found in exoskeletons of insects.

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Protein

1) Elements: Carbon, Hydrogen, Oxygen, Nitrogen2) Monomer:Amino acids3) Amino acids are joined together by peptide bond.4) Two molecules of amino acid combine to form dipeptides5) Many molecules of amino acid combine to form polypeptide6) Two type of Amino Acids:

a. Essential:- Cannot be synthesized by our bodyb. Non-essential:- Can be synthesized by our body

7) Two class of protein:a. First class proteins:- Protein that supple all the essential amino acids ( e.g.

meat, milk protein, eggs)

b. Second class proteins:- Protein that lacks of one or more essential aminoacids (e.g. graindm seeds, nuts)

8) Four level of protein structurea. Primary structure: Linear sequence of amino acidsb. Secondary Structure: Protein coiled into either -helix or -pleeted (e.g.keratin)c. Tertiary structure: Coiled protein are folded to form globular protein (e.g.

hormones, antibodies, albumin)

d. Quartenary structure: More than one polypeptide chain are folded tp formcomplex protein molecule (e.g. haemoglobin)

9) Function:a. Component of protoplasm and plasma membraneb. Structural protein such as keratin provide supportc. Storage protein such as albumin and casein provide amino acid for cell

growth

d.

Transport protein such as haemoglobin transport molecules around bodye. Contractile protein such as actin and myosin allows movementf. Enzyme catalyses chemical reactiong. Hormonal protein coordinate metabolic reactionh. Antibodies helps in defense mechanisms by destroying antigens

Lipids

1) Characteristic:a. Naturally occurring organic compoundb. Soluble in non-polar organic solventc. Hydrophobicd. Contain Carbon, hydrogen and oxygen

2) Examples:a. Fats and oils:

i. Stored energy (in adipose tissue) and Fat soluble vitamins (i.evitamins A,D,E,K)

ii. Fat synthesis: 3 fatty acids molecules each join to glycerol by anester linkage (a bond between a hydroxyl group and a carboxyl

group)

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Table: Differences between Saturated (Fats) and unsaturated (oils)

b. Phospholipids:-i. Function:structural component of cell membranesii. Is similar to fat but has only 2 fatty acids attached to glycerol rather

than 3.

iii. The 3rd hydroxyl group of glycerol is joined to phosphate group,

c. Steroids :-i. Examples: cholesterol and the sex hormones

ii. progesterone, testosterone and oestrogen regulate development ofsexual characteristics and gamate formation

d. axes:- provide protection for plants against water loss

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Enzyme

1) Enzyme are biological catalysts that can increase the rate of a biochemical reaction

2) Two type of enzyme:a. IntracellularEnzyme:- enzyme produce in cell and function within cellb. Extracellular enzyme:-enzyme produce in cell but is secreted to function

outside cell

3) The production of extracellular enzyme

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4) Factor affecting Enzyme activities

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Uses of enzyme in industry

Enzyme Uses

Amylase

Lipase

Protease

Cellulase

Zymase