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Title

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 2Lecture

Slides

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Chapter 2

The Chemical Basis of LifeThe Chemical Basis of Life

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Atomic Structure

Atoms: composed ofsubatomic particles

Neutrons: no electrical

charge

Protons: one positive charge

Electrons: one negative

charge

Nucleus: formed by protons

and neutrons

Most of the volume of an

atom occupied by electrons

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Isotopes and Atomic Mass Isotopes: two or more forms of same element with same

number of protons and electrons but different neutronnumber For example; there are three types of hydrogen

Denoted by using symbol of element preceded by mass number as1H, 2H, 3H

Atomic Mass: average mass of naturally occurringisotopes

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Electrons and Chemical Bonding Intramolecular bonding occurs

when outermost electrons are eithershared with or transferred toanother atom

Ionic Bonding: atomsexchange electrons

Covalent Bonding: two ormore atoms share electron pairs

Ion: an atom loses or gainselectrons and becomes charged

Cation: positively charged ion Anion: negatively charged ion

In an ionic bond, cations andanions are attracted to each otherand remain close to each other

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Intermolecular Forces:

Solubility and Dissociation

Solubility: ability of onesubstance to dissolve in another

For example, sugar or saltdissolves in water

DissociationorSeparation: inionic compounds, cations areattracted to negative end andanions attracted to positive endof water molecules; the ions

separate and each becomessurrounded by water molecules

Electrolyte: dissociation of anionic compound in water

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Electrolytes and Nonelectrolytes

Electrolytes: solutions made by the

dissociation of cations (+) and anions (-) in

water

Have the capacity to conduct an electric current

Currents can be detected by electrodes

Nonelectrolytes: solutions made by

molecules that dissolve in water, but do notdissociate; do not conduct electricity

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2.2 Chemical Reactions and Energy

Atoms, ions, molecules or compounds interact

to form or break chemical bondsReactants: substances that enter into a chemical

reaction.

Products: substances that result from the reaction

Chemical bonds are made (synthesis;anabolism) and broken (decomposition;catabolism) during chemical reactions

Metabolism: collective term used for the sumof all of the anabolic and catabolic reactions inthe body

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Synthesis Reactions Two or more reactants chemically combine to form a new and larger

product. Anabolism.

Chemical bonds made; energy stored in the bonds.

Responsible for growth, maintenance and repair

Dehydration: synthetic reaction where water is a product

Produce chemicals characteristic of life: carbohydrates, proteins, lipids, and

nucleic acids

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Decomposition Reactions A large reactant is broken down to form smaller products.

Catabolism. Chemical bonds broken; energy released.

Hydrolysis: water is split into two parts that contribute to theformation of the products

Example: the breakdown of ATP to form ADP and inorganicphosphate with a concomitant release of free energy

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Oxidation-Reduction Reactions

Oxidation: lossof an electron by a substance

Reduction: gainof an electron by a substance

Oxidation-Reduction Reactions: the complete or

partial loss of an electron by one substance isaccompanied by the gain of that electron by another

substance

Synthetic/decomposition reactions can be oxidation -

reduction reactions

Reactions can be described in more than one way

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ATP and Potential Energy

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Heat Energy

When a chemical bond is broken and

energy is released, only some of that energy

is used to manufacture ATP. Energy that is released but not captured is

released as heat.

Heat is used by mammals to maintain bodytemperature.

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Activation Energy and Enzymes

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2.3 Inorganic Chemistry

Inorganic Chemistry: generally,substances that do not contain carbon

Water, oxygen, calcium phosphate, metal ions

Exceptions: CO, CO2

, and HCO3

-

Organic Chemistry: study of carbon-

containing substances. Those that are

biologically active are called biochemicals.

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Acids and Bases; Salts and Buffers

Acid: a proton donor or any substance thatreleases hydrogen ions

Base: a proton acceptor or any substance

that binds to or accepts hydrogen ions Salt: a compound consisting of a cation

other than a hydrogen ion and an anion

other than a hydroxide ion. Example: NaCl Buffer: a solution of a conjugate acid-base

pair in which acid and base components

occur in similar concentrations

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Oxygen and Carbon Dioxide

Oxygen (O2): required in the final step in

the series of reactions used to extract energy

from food.

Carbon dioxide (CO2): produced during the

catabolism of organic compounds.

Metabolic waste product.

Combines with water in plasma and forms H+

thus affecting acid/base balance

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2.4 Organic Chemistry Carbohydrates: composed of carbon, hydrogen, oxygen.

Divided into monosaccharides, disaccharides, polysaccharides

Energy sources and structure

Lipids: composed mostly of carbon, hydrogen, oxygen. Relatively insoluble in water.

Functions: protection, insulation, physiological regulation,

component of cell membranes, energy source Proteins: composed of carbon, hydrogen, oxygen,

nitrogen, sometimes iodine. Functions: regulate processes, aid transport, protection, muscle

contraction, structure, energy

Nucleic Acids: composed of carbon, hydrogen, oxygen,nitrogen, phosphorus. Examples: ATP, DNA, RNA

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Carbohydrates: Monosaccharides Simple sugars.

Six-carbon sugars like glucose, fructose, and galactose are

important in the diet as energy sources.

Five-carbon sugars are components of ATP, DNA and RNA

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Carbohydrates: Disaccharides

Two simple sugars bound together by dehydration Examples: sucrose, lactose, maltose

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Carbohydrates: Polysaccharides

Long chains of many monosaccharides. Storage molecules for monosaccharides and form part ofcell surface markers

Glycogen formed by animals.

Starch and cellulose formed by plants Starch in food is used as a source of monosaccharides

Cellulose in food acts as fiber (bulk) in the diet

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Lipids: Fats Ingested and broken down by hydrolysis

Triglycerides: composed of glycerol and fatty acids Functions: protection, insulation, energy source

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Lipids: Phospholipids

Polar (hydrophilic) at one end; nonpolar (hydrophobic) at the

other.

Function: important structural component of cell membranes

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Lipids: Eicosanoids and

Fat-soluble Vitamins Eicosanoids: Derived from fatty acids.

Function: Important regulatory molecules

Include thromboxanes, leukotrienes, and

prostaglandins

Fat-soluble Vitamins: nonpolar molecules

essential for normal functioning.

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Lipids: Steroids

Cholesterol, bile salts, estrogen, testosterone. Carbon atoms arranged in four rings

Functions: physiological regulators and component of cell

membranes

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Enzymes Lower the activation energy necessary for a

reaction to occur; bring reactants into closeproximity

Three-dimensional shape contains an active sitewhere reactants attach.

Induced Fit Hypothesis: enzymes change shapeto accommodate the shape of specific reactants

Enzyme names usually end in ase and often havethe same word stem as the reactant; for example alipid is a reactant for lipase.

Cofactors: combine with active site and makenonfunctional enzymes functional

Organic cofactors called coenzymes

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Nucleic Acids DNA and RNA

Nucleotides Composed of a five-carbon sugar, a nitrogenous base, and a phosphate

Include the nucleic acids (DNA and RNA) and ATP

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DNA: Deoxyribonucleic acid

Genetic material of cells copied from one generation to next Composed of 2 strands of nucleotides

Each nucleotide contains one of the organic bases of adenine or guanine (which

are purines) and thymine or cystosine (which are pyrimidines).

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