Chapter 2Chemical Basis of Life

Why study chemistry in an Anatomy and Physiology class?

- body functions depend on cellular functions

- cellular functions result from chemical changes

- biochemistry helps to explain physiological processes, and develop new drugs and methods for treating diseases

2-2

Structure of Matter

Matter –

Elements – composed of chemically identical atoms• bulk elements –•trace elements –

Atoms – smallest particle of an element

2-3

Molecules and Compounds

Molecules – particle formed when two or more atoms chemically combine

Compound – particle formed when two or more atoms of different elements chemically combine

Molecular formulas – depict the elements present and the number of each atom present in the molecule

H2 C6H12O6 H2O

2-7

Ionic Bond

• an attraction between a cation and an anionIonic Bond

• formed when electrons are transferred from one atom to another atom

Ionic.ram

Covalent Bond

Formed when atoms share electrons

•Hydrogen atoms form single bonds•Oxygen atoms form two bonds•Nitrogen atoms form three bonds•Carbon atoms form four bonds

H ― HO = ON ≡ NO = C = O

2-11

Covalent.ram

Structural Formula

Structural formulas show how atoms bond and are arranged in various molecules

2-12

Polar Molecules

Polar Molecule• • results when electrons are not shared equally in covalent bonds• water is an important polar molecule

2-13

Hydrogen Bonds

Hydrogen Bond• a weak attraction between the positive end of one polar molecule and the negative end of another polar molecule• formed between water molecules• important for protein and nucleic acid structure

2-14

Chemical Reactions

Chemical reactions occur when chemical bonds form or break among atoms, ions, or molecules

Reactants-

Products-

NaCl ’ Na+ + Cl-

Reactant Products2-15

Types of Chemical Reactions

Synthesis Reaction – A + B ’ AB

Decomposition Reaction – AB ’ A + B

Exchange Reaction – AB + CD ’ AD + CBReversible Reaction –

A + B AB

2-16

Acids, Bases, and SaltsElectrolytes – substances that release ions in water

Acids – electrolytes that release hydrogen ions in waterHCl H+ + Cl-

Bases – substances that release ions that can combine with hydrogen ions

NaOH Na+ + OH-

Salts – electrolytes formed by the reaction between an acid and a base

NaCl Na+ + Cl-

HCl + NaOH H2O + NaCl 2-17

Acid and Base Concentrations

pH scale - indicates the concentration of hydrogen ions insolution

Neutral – pH 7; indicates equal concentrations of H+ and OH-

Acidic – pH less than 7; indicates a greater concentration of H+

Basic or alkaline – pH greater than 7;indicates a greater concentration of OH- 2-18

Organic Versus InorganicOrganic molecules

• contain C and H• carbohydrates, proteins, lipids, and nucleic acids

Inorganic molecules • generally do not contain C•water, oxygen, carbon dioxide, and inorganic salts

2-19

Inorganic Substances

Water • • • major component of all body fluids• medium for most metabolic reactions• important role in transporting chemicals in the body• can absorb and transport heat

Oxygen (O2) •-• -necessary for survival 2-20

Inorganic Substances

Carbon dioxide (CO2)• • must be removed from the body

Inorganic salts• abundant in body fluids• sources of necessary ions (Na+, Cl-, K+, Ca2+, etc.)• play important roles in metabolic processes

2-21

Organic SubstancesCarbohydrates

• provide energy to cells• supply materials to build cell structures• water-soluble• contain C, H, and O• ratio of H to O close to 2:1 (C6H12O6)• monosaccharides – glucose, fructose• disaccharides – sucrose, lactose• polysaccharides – glycogen, cellulose

2-22

Organic SubstancesCarbohydrates

2-23

Organic SubstancesLipids

• soluble in organic solvents• fats (triglycerides)

• used primarily for energy• contain C, H, and O but less O than carbohydrates (C57H110O6)• building blocks are 1 glycerol and 3 fatty acids per molecule• saturated and unsaturated

2-24

Organic SubstancesLipids

• phospholipids • building blocks are 1 glycerol, 2 fatty acids, and 1 phosphate per molecule

• hydrophilic and hydrophobic

• major component of cell membranes

2-25

Organic SubstancesLipids

• phospholipids • building blocks are 1 glycerol, 2 fatty acids, and 1 phosphate per molecule

• hydrophilic and hydrophobic

• major component of cell membranes

2-25

Organic Substances Lipids

• steroids• connected rings of carbon• component of cell membrane• used to synthesize hormones• cholesterol

2-26

Organic SubstancesProteins

• structural material• energy source• hormones• receptors• enzymes• antibodies• building blocks are amino acids

• amino acids held together with peptide bonds

2-27

Organic Substances Proteins

Four Levels of Structure

2-28

Organic SubstancesNucleic Acids

• constitute genes• play role in protein synthesis• building blocks are nucleotides

• DNA (deoxyribonucleic acid) – double polynucleotide• RNA (ribonucleic acid) – single polynucleotide 2-29

Organic SubstancesNucleic Acids

2-30DNA 2.mov DNA 3.mov DNA 4.mov

Clinical ApplicationsRadioactive Isotopes Reveal Physiology

• can be detected in the body using a scintillation counter

• injected into the body• different types taken up by different organs

• can be used to destroy specific tissues• commonly used

• iodine-131 for thyroid function• thallium-201 for heart function• gallium-67 and cobalt-60 for cancer• others used to assess kidney functions, measure hormone levels and bone density changes 2-31