2-1 Chapter 2 Lecture Outline See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes. Copyright (c) The McGraw-Hill.

2-1

Chapter 2

Lecture Outline

See PowerPoint Image Slides

for all figures and tables pre-inserted into

PowerPoint without notes.

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

2-2

The Chemistry of Life

• Atoms, Ions and Molecules• Water and Mixtures• Energy and Chemical

Reactions• Organic compounds

2-3

Atoms, Ions and Molecules

• The chemical elements

• Atomic structure

• Isotopes and radioactivity

• Ions, electrolytes and free radicals

• Molecules and chemical bonds

2-4

The Chemical Elements

• Element = simplest form of matter with unique chemical properties

• Atomic number = # of protons in nucleus– periodic table

• elements arranged by atomic number

– 24 elements have biological role• 6 elements = 98.5% of body weight • trace elements in minute amounts

2-5

2-6

Minerals

• Inorganic elements absorbed from soil by plants

• Equals 40% of body weight– structure (teeth, bones, etc)– enzymes

2-7

Structure of an Atom• Nucleus = center of atom

– protons: single + charge, mass = 1 amu– neutrons: no charge, mass = 1 amu

• Electron shells surround the nucleus– electrons: single negative charge, little mass– valence electrons in the outermost shell

• interact with other atoms• determine chemical behavior

2-8

Planetary Models of Elements

p+ represents protons, no represents neutrons

2-9

Isotopes and Radioactivity

• Isotopes– differ in # of neutrons– extra neutrons increase atomic weight– isotopes of an element are chemically

similar• have same valence electrons

• Atomic weight– average atomic mass of the isotopes

2-10

Radioisotopes and Radioactivity

• Isotopes – same chemical behavior, differ in physical behavior– breakdown gives off radiation

• Radioisotopes – unstable isotopes– every element has at least one radioisotope

• Radioactivity – radioisotopes decay to stable isotopes releasing

radiation– we are all mildly radioactive

2-11

Marie Curie

• First woman in world to receive a Ph.D.• First woman to receive Nobel Prize (1903)

– discovered radioactivity of radium– trained physicians in use of X rays and

radiation therapy as cancer treatment

• Died of radiation poisoning at 67

2-12

• Radiation ejects electrons forming ions• Destroys molecules and produces free radicals

– sources include:• UV light, X rays, nuclear decay (, , )

particle (dangerous if inside the body)– 2 protons + 2 neutrons can’t penetrate skin

particle (dangerous if inside the body)– free electron - penetrates skin a few millimeters

particle (emitted from uranium and plutonium) – penetrating; very dangerous gamma rays

Ionizing Radiation

2-13

• Physical half-life of radioisotopes– time needed for 50% to decay– nuclear power plants create radioisotopes

• Biological half-life of radioisotopes– time for 50% to disappear from the body– decay and physiological clearance

• Radiation exposure in sieverts (Sv)– background radiation = radon gas and

cosmic rays– sources = X rays and radiation therapy

Ionizing Radiation 2

2-14

• Ions - carry a charge due to an unequal number of protons and electrons

• Ionization = transfer of electrons from one atom to another ( stability of valence shell)

Ions and Ionization

2-15

• Anion – atom that gained electrons (net negative charge)

• Cation– atom that lost an electron (net positive charge)

• Ions with opposite charges are attracted to each other

Anions and Cations

2-16

Electrolytes

• Salts that ionize in water to form body fluids– capable of conducting electricity

• Electrolyte importance– chemical reactivity– osmotic effects (influence water movement)– electrical effects on nerve and muscle tissue

• Imbalances cause muscle cramps, brittle bones, coma and death

2-17

2-18

Free Radicals

• Particle with an odd number of electrons

• Produced by – normal metabolic reactions, radiation,

chemicals • Causes tissue damage

– reactions that destroy molecules– causes cancer, death of heart tissue and

aging

• Antioxidants– neutralize free radicals– in diet (vitamin E, carotenoids, vitamin C)

2-19

Molecules and Chemical Bonds

• Molecules– two or more atoms covalently bonded

• Compounds– two or more atoms of different elements

covalently bonded

• Molecular formula – elements and how many atoms of each

• Structural formula– location of each atom– structural isomers revealed

2-20

• Molecular formulae are identical, but structural formulas differ for grain alcohol and ether

Structural Formula of Isomers

2-21

Molecular Weight

• MW of compound = sum of atomic weights of atoms

• Calculate: MW of glucose (C6H12O6)

6 C atoms x 12 amu each = 72 amu

12 H atoms x 1 amu each = 12 amu

6 O atoms x 16 amu each = 96 amu

Molecular weight (MW) = 180 amu

2-22

Chemical Bonds

• Ionic bonds

• Covalent bonds

• Hydrogen bonds

• Van der Waals force

2-23

Ionic Bonds

• Attraction of oppositely charged ions • No sharing of electrons

• Weak bond (easily dissociates in water)

2-24

Covalent Bonds

• Formed by sharing of valence electrons

• Types of covalent bonds– single = sharing of single pair electrons– double = sharing of 2 pairs– nonpolar

• shared electrons (equal time around each nucleus)• strongest of all bonds

– polar• negative charge where electrons spend most time

2-25

Single Covalent Bond

• One pair of electrons are shared

2-26

Double covalent bonds: Two pairs of electrons are shared each C=O bond

2-27

electrons shared equally

electrons shared unequally

Nonpolar /Polar Covalent Bonds

2-28

Hydrogen Bonds• Weakest bond = no sharing of

electrons• Attraction between polar molecules

– positive hydrogen atoms to negative oxygen atoms in a 2nd molecule

• Physiological importance– properties of water created by shapes of

large complex molecules – determined by folding due to hydrogen

bonds

2-29

Hydrogen Bonding in Water

2-30

Van der Waals Forces

• Weak attractions between neutral atoms

• Fluctuations in electron density create polarity

• Only 1% as strong as a covalent bond– folding of large molecules– significant when 2 large surfaces meet

2-31

Mixtures and Water

• Substances physically but not chemically combined

• Mixtures in our bodies contain water

• Water 50-75% of body weight– depends on age, sex, percentage body fat,

etc.

2-32

Solvency

• Solvency - ability to dissolve other chemicals– Hydrophilic (charged substances) dissolve

easily in water– Hydrophobic (neutral substances) do not

easily dissolve in water

• Water = universal solvent– metabolic reactions and transport of

substances

2-33

Water as a Solvent

• Polar water molecules overpower the ionic bond in Na+Cl-

– forming hydration spheres around each ion – water molecules: negative pole faces Na+, positive

pole faces Cl-

2-34

Adhesion and Cohesion

• Adhesion – tendency of one substance to cling to another

• Cohesion – tendency of like molecules to cling to each other– water is very cohesive due to its hydrogen

bonds– surface film on water formed by surface

tension

2-35

Chemical Reactivity of Water

• Participation in chemical reactions– water ionizes into H+ and OH-

– water ionizes other chemicals (acids and salts)

– water involved in hydrolysis and dehydration synthesis reactions

2-36

Thermal Stability of Water

• Water stabilizes internal temperature – has high heat capacity

• hydrogen bonds inhibit temperature increases by inhibiting molecular motion

– water absorbs heat without changing temperature

– effective coolant• 1 ml of perspiration removes 500 calories

– calorie: amount of heat required to raise temperature of 1g of water by 1°C

2-37

Solutions

• Mixture of a solute into a solvent

• Small solute particles – pass through cell

membranes

• Solution transparent• Remains mixed

2-38

Colloids• Mixture of protein

and water– change from liquid

to gel state within and between cells

• Particles too large to pass through cell membranes

• Cloudy• Remains mixed

2-39

Suspensions and Emulsions

• Suspension– particles suspended in

a solvent– particles exceed 100nm

• too large to pass through a cell membrane

– cloudy or opaque appearance

– separates on standing• Emulsion

– suspension of one liquid in another

– fat in breast milk

2-40

2-41

Measures of Concentration• Weight per Volume

– weight of solute in given volume of solution

• IV saline: 8.5 grams NaCl/liter of solution

• Percentages– Weight/volume of solute in solution

• IV D5W (5% w/v dextrose in distilled water)– 5 grams of dextrose and fill to 100 ml water

• Molarity– moles of solute/liter in solution– physiologic effects based on number of

molecules in solution not on weight

2-42

Molarity

• Molecular weight in grams = 1 mole of molecules

• 1 mole = Avogadro’s number of molecules

• Molarity is the number of moles of solute/ liter of solution– MW of glucose is 180– one-molar (1.0M) glucose solution

contains 180g/L

2-43

• Molar– # of molecules equal– weight of solute

unequal

• Percentage– # of molecules

unequal– weight of solute

equal

Percentage vs. Molar Concentrations

2-44

Electrolyte Concentrations

• Effect the body chemically, physically and electrically– depends on charge and concentration

• Measured in equivalents– 1 Eq will electrically neutralize 1 mole of H+ or OH-

ions– multiply molar concentration x valence of the ion– 1 M Na+ = 1 Eq/L– 1 M Ca2+ = 2 Eq/L

2-45

Acids, Bases and pH

• An acid is proton donor (releases H+ ions)• A base is proton acceptor (accepts H+ ions)• pH = the concentration of H+ ions in

solution– a pH of less than 7 is acidic solution– a pH of greater than 7 is basic solution– a pH of 7.0 is neutral pH

2-46

pH

• pH = measurement of molarity of H+ [H+] on a logarithmic scale– pH = -log [H+] thus pH = - log [10-3] = 3– a change of one number on the pH scale

represents a 10 fold change in H+ concentration

• a solution with pH of 4.0 is 10 times as acidic as one with pH of 5.0

• Our body uses buffers to prevent change– pH of blood ranges from 7.35 to 7.45– tremors, paralysis or even death

2-47

pH Scale

2-48

Work and Energy

• Energy - capacity to do work

• Kinetic energy - energy of motion – heat is kinetic energy of molecular

motion

• Potential energy- energy due to object’s position (ions on one side only of cell membrane)– chemical energy - potential energy

stored in the molecular bonds

2-49

Chemical Reaction• Process that forms or breaks an

ionic or covalent bond

• Symbolized by chemical equation– reactants products

Classes of reactions

• Decomposition reactions

• Synthesis reactions

• Exchange reactions

2-50

Decomposition Reactions

• Large molecules broken down into smaller ones

• AB A + B

2-51

Synthesis Reactions

• Two or more small molecules combine to form a larger one

• A + B AB

2-52

Exchange Reactions• Two molecules collide and exchange

atoms or group of atoms

• AB+CD ABCD AC + BD

Stomach acid (HCl) and sodium bicarbonate (NaHCO3) from the pancreas combine to form NaCl and H2CO3.

2-53

Reversible Reactions

• Go in either direction (symbolized with double-headed arrow)

• CO2 + H2O H2CO3 HCO3- + H+

– most common equation discussed in this book

• Law of mass action determines direction– side of equation with greater quantity of

reactants dominates

2-54

Reaction Rates• Basis for reactions is molecular motion and

collisions– reactions occur when molecules collide with enough

force and the correct orientation

• Reaction Rates affected by:– concentration

• more concentrated, more collisions, faster rate

– temperature• higher temperature, greater collision force, faster rate

– Catalysts (enzymes)• speed up reactions without permanent change to itself• holds reactant molecules in correct orientation

2-55

Metabolism

• All the chemical reactions of the body• Catabolism

– energy releasing (exergonic) decomposition reactions

• breaks covalent bonds, produces smaller molecules, releases useful energy

• Anabolism– energy storing (endergonic) synthesis reactions

• requires energy input

2-56

Oxidation-Reduction Reactions

• Oxidation– molecule gives up electrons and releases

energy– accepting molecule is the oxidizing agent

• oxygen is often the electron acceptor

• Reduction– molecule gains electrons and energy– donating molecule is the reducing agent

• Oxidation-reduction (redox) reactions– Electrons are often transferred as hydrogen

atoms

2-57

2-58

Organic Chemistry

• Study of compounds containing carbon

• 4 categories of carbon compounds– carbohydrates– lipids– proteins– nucleotides and nucleic acids

2-59

Organic Molecules and Carbon

• Only 4 valence electrons– bonds readily to gain more valence

electrons

• Forms long chains, branched molecules and rings– serve as the backbone for organic

molecules

• Carries a variety of functional groups

2-60

• Atoms attached to carbon backbone

• Determines chemical properties

Functional Groups

2-61

Monomers and Polymers

• Macromolecules = very large molecules

• Polymers = macromolecules formed from monomers bonded together

• Monomers = an identical or similar subunit

2-62

Polymerization

• Bonding of monomers together to form a polymer

• Formed by dehydration synthesis– starch molecules are a polymer of 3000

glucose monomers– protein molecules are a polymer of amino

acids

2-63

Dehydration Synthesis• Monomers covalently bond together to form a

polymer with the removal of a water molecule– A hydroxyl group is removed from one monomer

and a hydrogen from the next

2-64

Hydrolysis• Splitting a polymer (lysis) by the addition of a water

molecule (hydro)– a covalent bond is broken

• All digestion reactions consists of hydrolysis reactions

2-65

Organic Molecules: Carbohydrates

• Hydrophilic organic molecule

• General formula – (CH2O)n n = number of carbon atoms

– for glucose, n = 6, so formula is C6H12O6

– 2:1 ratio of hydrogen to oxygen

• Names of carbohydrates– word root sacchar- or the suffix -ose often

used• monosaccharide or glucose

2-66

Monosaccharides

• Simple sugars

• General formula is C6H12O6

– structural isomers

• Major monosaccharides– glucose, galactose and

fructose– produced by digestion of

complex carbohydrates• glucose is blood sugar

2-67

Disaccharides• Sugar molecule

composed of 2 monosaccharides

• Major disaccharides– sucrose = table sugar

• glucose + fructose

– Lactose = sugar in milk• glucose + galactose

– Maltose = grain products• glucose + glucose

2-68

Polysaccharides• Chains of glucose subunits

• Starch: energy storage in plants– digestible by humans for energy

• Cellulose: structural molecule of plant cell walls– fiber in our diet

• Glycogen: energy storage in animals– liver synthesizes after a meal and breaks down

between meals

2-69

Carbohydrate Functions• All digested carbohydrates converted to glucose

and oxidized to make ATP• Conjugated carbohydrate = bound to lipid or

protein– glycolipids

• external surface of cell membrane

– glycoproteins• external surface of cell membrane• mucus of respiratory and digestive tracts

– proteoglycans• gels that hold cells and tissues together• joint lubrication• rubbery texture of cartilage

2-70

2-71

Organic Molecules: Lipids• Hydrophobic organic molecule

– composed of carbon, hydrogen and oxygen

• Less oxidized and thus has more calories/gram

• Five primary types in humans– fatty acids– triglycerides– phospholipids– eicosanoids– steroids

2-72

Fatty Acids

• Chain of 4 to 24 carbon atoms– carboxyl (acid) group on one end, methyl group on the other

and hydrogen bonded along the sides• Classified

– saturated - carbon atoms saturated with hydrogen – unsaturated - contains C=C bonds without hydrogen

2-73

Triglycerides (Neutral Fats)

• 3 fatty acids bonded to glycerol molecule (dehydration synthesis)

• At room temperature– when liquid called oils

• often polyunsaturated fats from plants

– when solid called fat• saturated fats from animals

• Function - energy storage, insulation and shock absorption

2-74

Phospholipids• Triglyceride with one fatty acid replaced by a

phosphate group• Amphiphilic character

– fatty acid “tails” are hydrophobic– Phosphate “head” is hydrophilic

2-75

Eicosanoids

• Derived from arachidonic acid (a fatty acid)• Hormone-like chemical signals between cells• Includes prostaglandins – produced in all

tissues– role in inflammation, blood clotting, hormone

action, labor contractions, blood vessel diameter

2-76

Steroids and Cholesterol

• Steroid = lipid with carbon atoms in four rings– all steroids are derived from cholesterol

• cortisol, progesterone, estrogens, testosterone and bile acids

• Cholesterol – important component of cell membranes – produced only in animal liver cells

• naturally produced by our body

2-77

2-78

Organic Molecules: Proteins• Protein = polymer of amino acids

• Combination determines structure and function

• Amino acid = carbon with 3 attachments– Amino (NH2), carboxy (COOH) and radical

group (R group)

• 20 unique amino acids– -R groups differ– properties determined by -R group

2-79

Naming of Peptides• Peptide = polymer of 2 or more amino

acids• Named for the number of amino acids

– dipeptides have 2, tripeptides have 3– oligopeptides have fewer than 10 to 15 – polypeptides have more than 15– proteins have more than 100

2-80

Dipeptide Synthesis

•Dehydration synthesis creates a peptide bond that joins amino acids

2-81

Protein Structure and Shape

• Primary structure – amino acid sequence

• Secondary structure– coiled or folded shape– hydrogen bonds between negative C=O and positive

N-H groups

• Tertiary structure – further folding and bending into globular and fibrous

shapes

• Quaternary structure– associations of two or more separate polypeptide

chains

2-82

2-83

• Contain a non-amino acid moiety

• Hemoglobin contains complex iron containing ring called a heme moiety

Conjugated Proteins

2-84

Protein Conformation and Denaturation

• Conformation – unique 3-D shape crucial to function– ability to reversibly change their conformation

• opening and closing of cell membrane pores

• Denaturation– conformational change that destroys function

• extreme heat or pH

2-85

Protein Functions• Structure

– collagen, keratin

• Communication– some hormones, cell receptors

• Membrane Transport– channels, carriers

• Catalysis– enzymes

2-86

Protein Functions 2

• Recognition and protection– antigens, antibodies and clotting proteins

• Movement– molecular motor = molecules that can change

shape repeatedly

• Cell adhesion– proteins bind cells together

2-87

Enzymes

• Proteins as biological catalysts – promote rapid reaction rates

• Substrate - substance an enzyme acts upon

• Naming Convention– named for substrate with -ase as the suffix

• amylase enzyme digests starch (amylose)

• Lowers activation energy = energy needed to get reaction started– enzymes facilitate molecular interaction

2-88

Enzymes and Activation Energy

2-89

Steps of an Enzyme Reaction

• Substrate approaches enzyme molecule

• Substrate binds to active site forming enzyme-substrate complex– highly specific

• Enzyme breaks bonds in substrate

• Reaction products released

• Enzyme repeats process over and over

2-90

Enzymatic Reaction Steps

2-91

• Reusability of enzymes– enzymes are unchanged by the reactions

• Astonishing speed– millions of molecules per minute

• Temperature and pH– change shape of enzyme and alter its ability to

bind– enzymes vary in optimum pH

• salivary amylase works best at pH 7.0• pepsin works best at pH 2.0

– temperature optimum for human enzymes = body temperature

Enzymatic Action

2-92

Cofactors and Coenzymes

• Cofactors– nonprotein partners (iron, copper, zinc,

magnesium or calcium ions) – bind to enzyme and change its shape– essential to function

• Coenzymes– organic cofactors derived from water-soluble

vitamins (niacin, riboflavin)– transfer electrons between enzymes

2-93

Coenzyme NAD+

• NAD+ transports electrons from one metabolic pathway to another

2-94

Metabolic Pathways• Chain of reactions, each catalyzed by an

enzyme• A B C D• A is initial reactant, B+C are intermediates

and D is the end product• Regulation of metabolic pathways

– activation or deactivation of the enzymes – cells can turn on or off pathways

2-95

Organic Molecules: Nucleotides

• 3 components– nitrogenous base– sugar (monosaccharide)– one or more phosphate groups

• Physiological important nucleotides – ATP = energy carrying molecule– cAMP = activates metabolic pathways– DNA = carries genetic code – RNA = assists with protein synthesis

2-96

ATP (Adenosine Triphosphate)

ATP contains adenine, ribose and 3 phosphate groups

2-97

ATP• Holds energy in covalent bonds

– 2nd and 3rd phosphate groups have high energy bonds ~

• ATPases hydrolyze the 3rd high energy phosphate bond– separates into ADP + Pi + energy

• Phosphorylation– addition of free phosphate group to another

molecule

2-98

Overview of ATP Production

• ATP consumed within 60 seconds• Continually replenished

2-99

Other Nucleotides

• Cyclic adenosine monophosphate (cAMP)– formed by removal of both high energy Pi’s

from ATP– formation triggered by hormone binding to cell

surface– cAMP becomes “second messenger” within

cell– activates effects inside cell

2-100

Nucleic Acids

• DNA (deoxyribonucleic acid)– 100 million to 1 billion nucleotides long– contains genetic code

• cell division, sexual reproduction, protein synthesis

• RNA (ribonucleic acid) – 3 types– transfer RNA, messenger RNA, ribosomal RNA– 70 to 10,000 nucleotides long– involved in protein synthesis coded for by

DNA