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Lecture Outline - Chapter 2

THE CHEMICAL BASIS OF LIFE

I. Basic Chemistry

A. A basic knowledge of chemistry is essential to understanding anatomy and

physiology

B. All of the functions of the body are the result of chemical reactions.

1. Digestion, muscle contrac tion, metabolism and generation of nerve

impulses can all be described as chemical reactions.

2. A review of basic chemical principles, terminology and symbols will

make anatomy and physiology more understandable.

II. Matter M ass and Weight

A. Matte r and the Elements

1. Matter = anything that occupies space and has mass.

2. Mass = the amount of matter in an object

3. Weight = is the gravitational force acting on an object of a given

mass.

4. Elements = simplest form of matter with unique chemical properties

a. 112 known elements (92 naturally occurring)

5. Atom = the smallest particle of an element that has the chemical

characteristics of that element and are the smallest units of matter that

can undergo chemical change.

a. An element is composed of atoms of only one kind.

b. Each element or atom is represented by a symbol

B. Atomic Structure

1. Three major subatomic structures make up a toms

a. Neutrons:

(1) no electric charge, mass = 1 Dalton

b. Protons :

(1) positive charge, 1 Dalton

c. Electrons

(1) negative charge

(2) equal in magnitude to positive charge of proton

(3) mass = 1/2000 Dalton

2. Atoms generally have equal numbers of protons and electrons thus

the charges cancel each other out leaving the a tom e lectrically

neutral.

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3. Protons and neutrons from the nucleus of the a tom.

a. the nucleus make up more than 99.9% of the mass.

4. Electron are located outside of the nucleus

a. Most of the volume of the atom is occupied by the electron

b. electron density diagram: predict where an electron is most

likely to be found at any given moment.

C. Atomic Number and mass

1. atomic number = the number of protons in its nucleus.

2. Each proton or neutron weighs one atomic mass unit or Dalton

3. mass number = the number of protons p lus the number of neutrons

for an element.

4. Electrons determine the chemical properties of the atom.

5. When the number of protons and number of neutrons are equal, the

atom is electrically neutral.

6. Electron shells - Electrons encircle the nucleus in electron shells or

energy levels.

a. Orbita l - an e lectron can occupy any position in a certa in

volume of space ca lled an orb ital.

b. Orbital is like a shell beyond which electrons don’t pass.

c. The innermost she ll can hold up to two electrons.

d. The oute rmost she ll, holding the valence electrons, can have

eight electrons.

D. Isotopes and Atomic Mass

1. Isotopes are two or more forms of the same element that have the

same number of protons and electrons but vary in their numbers of

neutrons.

a. Same atomic number but different mass numbers.

b. Eg. 3 isotopes of hydrogen:

(1) hydrogen - 0 neutrons written ( 1H) symbol with mass

number

(2) deuterium - 1 neutron (2H)

(3) tritium - 2 neutrons (3H).

2. All isotopes of the same element behave the same chemically.

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3. Atomic Mass

a. Individual atoms have very little mass.

(1) Eg. Hydrogen = 1.67 X 10 -24g.

b. To avoid us ing such small numbers w e use a system of relative

atomic mass

(1) Unified atomic mass units (u) or Dalton (D)

c. Each proton or neutron has an atomic mass of 1 .

(1) C12 is used as the standard

(a) One atomic mass unit Equals 1 /12 the mass of Carbon

(6 protons and 6 neutrons)

(2) The atomic mass = the average mass of its naturally

occurring isotopes taking into account the relative

abundance of each isotope.

(a) Ie. Carbon has the isotopes 12C, 13C and 14C.

(b) The atomic mass of Carbon is 12.01 D

(c) Slightly above 12 because of small amounts of 13C and14C.

E. Electrons and chemical bonding

1. The chemical behavior of an atom is de termined largely by its

outermost electrons (valence electrons ).

2. A chemical bond is an attrac tion between atoms usually to form

stable valence shells

a. An atom is most stable w hen the va lence shell is full.

3. Chemical bonding occurs w hen the outermost electrons a re

transferred or shared between atoms.

4. The number of bonds an atom can make depends on the number of

elec trons in its oute rmost orb ital.

5. Chemical bonding can be grouped into three categories

a. Ionic , covalent, and metallic

6. Ionic Bonding

a. If an atom loses or gains electrons it is no longer electrically

neutral (carries a charge) and is called an ion.

(1) Ions are charged particles.

(2) Eg. If an atom of Na loses an electron it becomes

positively charged (Na+). Or if an atom of Cl gains and

electron it will become negatively charged (Cl-).

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b. cations - Positively charged ions ( have lost an e lectron)

c. anions - Negatively charged ions are called(have gained an

electron)

d. Oppositely charged molecules are attracted to each other

and tend to remain close to each other.

e. Ionic bonding occurs w hen one or more valence e lectrons

from one atom are complete ly transferred to a second atom.

(1) electrons are not shared

(2) Eg. Na+ and Cl- ions are held toge ther by ionic

bonding to form an a rray of ions ca lled N aCl or table

salt.

(a) Na - 11 e- (2 + 8 + 1)

(b) Cl- 17 e- (2+ 8 + 7)

f. Common ions found in the body include:

(1) Ca++, Na+, K+, H+, OH-, Cl-

g. Ionic compounds readily form crystals.

h. Ionic bonds a re weak because ions tend to dissocia te in

water.

7. Covalent Bonding

a. Covalent bonding results when atoms share one or more

pairs of valence electrons to form stable valence shells.

(1) The resulting structure is called a molecule.

b. Eg. Two hydrogen molecules from a molecule. H-H

(1) Each H has one electron, as the two H move close

together the positive nucleus is attracted to the neg.

electrons.

(2) At an optimal distance the two H atoms begin sharing

electrons.

(3) The two atoms are now held together by a covalent

bond.

c. single covalent bond is formed when one elec tron pair is

shared between two atoms

d. A double covalent bond is formed when two atoms share 4

electrons, two from each atom

(1) Eg. O=O, CO2 (O=C=O)

e. Polar and non polar covalent bonds

(1) nonpolar covalent bond is formed when electrons are

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shared equally between atoms

(2) polar covalent bonds are formed when the electrons

are not shared equally but a re attracted more strongly

by one nucleus than the other.

(a) Eg. H2O – oxygen attracts elec trons more strongly

than H. (oxygen side of molecule is more

negative)

(b) Oxygen, nitrogen and phosphorus have a strong

tendency to pull electrons toward themselves.

8. Metalic bonding

a. In metalic bonding the outermost shell of electrons is shared

equally among all of the atoms in the sample.

b. The electrons form a “sea of electrons

c. Elec trons move freely between nucle i of atoms. For this

reason metals are excellent conductors of electricity.

F. Molecules and Compounds

1. Molecule - two or more atoms chemically combined form a

molecule.

2. Molecular formula’s - symbol of atom and subscript number of

that specific atom in the molecule.

a. Eg. C6H12O6 (sugar)

b. Molecule can be made of two atoms of the same kind (O2 or

H2) or of different kinds

3. Compound - is a substance composed of two or more different

types of atoms that are chemically combined.

a. H2 is not a molecule because it is not made or two or more

different kinds of atoms.

b. H2O is a compound

G. Intermolecular forces

1. Result form weak elec trostatic attractions betw een the

oppos itely charged parts of different molecules o r between ions

and molecules

a. These forces are much weaker than the chemical bonds we have

just talked about

b. Molecules with polar covalent bonds have positive and negative

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ends.

(1) The pos itive end of one molecule will be attracted to the

negative end of another. (Eg. H2O)

2. Hydrogen bonds are formed w hen oppositely charged ends of one

polar molecule are attracted to another polar molecule

a. A weak hydrogen bond forms be tween the slightly positive

hydrogen of one molecule and the slightly negative oxygen or

nitrogen portion of another.

b. Hydrogen bonds are important for maintaining the

three-dimensiona l structure of large, b iologically important

molecules.

H. Solubility and Dissoc iation

1. The ability of a substance to dissolve is called solubility.

a. Charged and polar substances ( Na+ , Cl-, glucose dissolve

readily in water.

b. Nonpolar substances such as oils do not dissolve.

2. Ionic compounds dissolve in water because their ions dissociate or

separate from each other

a. There cations are attracted to the negative ends of water

molecules

b. There anions are attracted to the positive ends of the water

molecule.

3. Covalent compounds generally remain intact in water even though

they are surrounded by water.

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CHEMICAL REACTIONS

I. Atoms, Ions molecules compounds interact to form or break chemical

bonds.

1. Reac tants: substances that enter a reac tions

2. Products : resulting products o f a reactions

a. Reactants º Products

J. Synthesis Reactions

1. 2 or more chemical combine to form new and larger produc ts

a. Eg. 2 amino acids ºdipeptide + H2O ( dehydration)

b. ADP + Pi º ATP

2. Synthesis reactions within the body are refereed to as anabolic.

(Anabolism).

K. Decom position Reactions

1. Large reactants are chemically broken down into two or more smaller

products .

a. Eg. Disacharide + H2O º 2 X glucose (Hydrolysis).

2. catabolism - Decomposition reactions that occur in the body are

refereed to as .

3. All of the anabolic and catabolic reactions in the body collective ly are

defined as Metabolism

L. Oxidation - R eduction Reactions

1. Chemical reaction that results from the exchange of electrons

a. Oxidation - loss of an elec tron by an atom.

b. Reduction - gain of an electron by an atom.

2. Because the loss of an electron by one atom is accompanied by the

gain of an electron in another atom these reactions are called

Oxidation - Reduction Reactions.

M. Reversible reactions

1. Chemical reactions in which the reaction can proceed from reactants

to produc ts and products to reactants

a. A + B º C + D

b. Equilibrium the point at which product formation is equal to the

rate of the reverse reac tion.

c. Eg. CO2 + H2O º H2CO3 º H+ + HCO3-

(1) H2CO3- carbonic acid; HCO3-- bicarbona te

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N. Rate of Chemical Reactions

1. Rate is influenced by several factors:

a. Reactants - differ in their ability to undergo chemical reactions.

b. Concentration - greater concentrations of reactants generally

cause reac tions to proceed faster.

c. Temperature - reaction speed increases with higher temps.

(Molecules move faster - bump into each other more.

d. Catalysts - substance that increases the rate at which a chemical

reaction proceeds.

(1) Enzymes - are prote in molecules that ac t as cata lysts in the

body.

III. ENERGY

A. Energy is defined as the capacity to do work.

B. Two forms of energy:

1. Potential energy - s tored energy

a. eg. coiled spring - has potential to do work but no work is

accomplished.

2. Kinetic energy - form of energy that actually does work.

a. eg. uncoiling spring pushing an object.

C. Energy can neither be created or destroyed

1. However potential energy can be converted to kinetic energy and vice

versa.

D. Energy can take several forms.

1. Electric Energy - movement of ions or electrons

a. Eg. nervous impulse - movement of ions across a membrane.

2. Electromagnetic Energy - energy that moves in waves (pebble in a

pond)

a. elec tromagnetic waves are dis turbances of elec tric o r magnetic

fields.

b. variety of wave types depending on wavelength.

(1) X- ray, ultraviolet, vis ible light, infrared, microwave, radio

waves.

3. Chemical Energy - result from the relative positions and interac tions

among charged subatomic particles.

a. Similarly charged particle close together have high potential

energy.

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b. Our bodies use chemical energy in the form of food. The

potential energy between food and waste products is used for

growth repair movement and heat prodution within the body.

c. Metabolism - in metabolism ionic and covalent chemical bonds

are formed and broken .

(1) The relative positions of electrons and nuclei changes

producing changes in chemical energy.(FIG 2.11)

(a) Formation of chemical bonds results in a increase of

potential energy and requires the input of energy.

i) ADP + Pi + energy ºATP

ii) energy comes from the chemical bonds in food.

(2) Breaking a chemical bond results in an decrease of potential

energy and results in the release of energy.

(a) ATP º ADP + Pi + energy

d. Photosynthesis - process by which plants capture energy in

sunlight and incorporate it into chemical bonds

4. Mechanical energy- energy resulting form the position or movement

of an objec t.

a. In the body, chemical energy is converted into mechanical

energy that results in body movement ie. walking, beating heart.

5. Heat energy

a. Heat is the energy that flows between objects that are at

different temperatures.

b. Heat is always transferred from a hotter object to a cooler object

c. All other forms of energy can be converted to heat energy.

(1) When a moving object comes to rest the kinetic energy of

the objec t is converted to heat energy by friction.

(2) Potential energy in chemical bonds can also be released as

heat energy during chemical reactions.

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IV. INORGANIC CHEMISTRY

Inorganic chemistry - deals with those substance that do not contain carbon

Organic chemistry - the study of carbon-containing substances

Exceptions: carbon monoxide and carbon dioxide are considered inorganic.

A. Water

1. 67% of body is water

a. Water is a polar molecule and forms hydrogen bonds.

b. These hydrogen bonds organize water molecules into a lattice

that holds the waster molecules together.

2. Water has properties that are well suited for many functions in living

organisms:

a. Stabilizing body temperature

(1) Water has a high specific heat

(a) A relatively large amount o f heat is required to change

the temperature.

(b) Tends to resist large temperature fluctuations.

(2) Water evaporates (changing from a liquid to a gas) - this

requires heat (540 calories/ gram)

(a) Evapora tion of swea t therefore effectively rids the

body of excess hea t.

b. Protection

(1) Water is an effective lubricant

(a) Prevents damage due to friction (eg. eye against

eyelid)

(b) Provides a cushion around organs (eg C SF and bra in)

c. Chemical reactions

(1) Water is an excellent so lvent.

(a) Many reacting molecules must be dissolved in water

within the body before they can react.

(2) Dehydration and hydrolysis reactions require water.

d. Mixing medium

(1) Water can mix with other solutions to form solutions,

suspensions and colloids

(a) solutions: any liquid that contains dissolved substances

(eg. Sweat contains NaCl etc.

(b) suspens ions: a liquid that contains non-dissolved

materials that set tle out of o f the liquid unlesss it is

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continually shaken. (Eg. Blood)

(c) colloid: a liquid tha t contains nondissolved materials

that do not settle out o f liquid. (Water and pro teins

inside the cell).

B. Solution Concentrations

1. Solutions are made up of a solvent (the liquid portion) and solutes

(substances dissolved in the solvent).

2. The concentration of a solution can be expressed in a number of

different ways:

a. As a percentage (ie. A 10% solution equals 10 g of solute in 100

ml of solution etc. )

b. As a osmolarity (1 osmole = 1 mole (Avegadros’s # of particles)

in 1 kilogram of water)

(1) Osmolarity is a re flection of the number of particles in a

solution and not the type of particle in a solution.

(2) The osmolarity of body fluids is important because it

influences the movement of water in and out of cells.

(3) Note: difference between molality and osmolality is that

osmolality takes into acount the number of particles a

molecule breaks into when it goes into solution. (A 1 molar

solution of NaCL = a 2 osmoler solution of NaCL because

the Na+ and Cl- are separated in water.)

C. Acids and Bases

1. Acid : defined as a proton donor.

a. A Hydrogen atom without its electron is a proton doner

(H+)–any substance tht releases H+ ion is therefore considered

and acid.

(1) eg. HCl º H+ + Cl- (HCl is an acid because it gives up H+

when put into solution.)

2. Base: defined as a proton acceptor

a. Any substance that binds to hydrogen ions is a base.

(1) eg. NaOH ºNa+ + OH- OH- + H+ ºH2O (hydroxide

ions are proton acceptors)

3. The more freely the acid or base dissociates the stronger it is.

a. Strong ac id : HC l ºH+ Cl-

(1) dissociates almost completely and therefore is a strong acid.

b. Weak Acid : Acetic acid CH3COOH º CH3COO- + H +

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(1) Some dissociates and some does not.

(2) An equilibrium is reached between the ions and the

undissociated weak acid.

4. The pH Scale

a. The pH scale is a means of referring to the H+ content of a

solution.

b. Pure water is defined as neutral and has a pH of 7.

(1) Has an equal concentration of H+ and OH- ions

c. Solutions with a pH less than 7 are acidic (have a higher

concentration of H+ than OH-)

d. Solutions wtih a pH greater than 7 are basic or alkaline ( have

lower concentration of H+ compared to OH-).

e. pH stands for the power or H concentration.

(1) logarithmic scale - a change of pH by one unit represents a

10 fold change in the concentra tion of H+.

(2) pH of 6 has a 10 times as many H+ ions than a solution

with a pH of 7 and 100 times as many H+ ions as pH 8.

5. Salts

a. A salt is compound consisting of a cation other than H+ and an

anion other than a hydroxide ion.

b. Typically, when salts such as NaCl dissociate in ater hey form

positively and negatively charged ions.

6. Buffers

a. The chemical nature of many molecules changes as the pH of a

solution in which they are dissolved changes.

(1) eg. Most enzymes work within a narrow pH range.

(2) Survival of an organism depends on its ability to mainta in it

pH level within a narrow range.

b. The body uses buffers to regulate pH levels.

c. Buffer: solution of a conjuga ted acid-base pair in w hich the acid

component and the base component occur in similar

concentra tions.

(1) A conjugate base is a ll that remains of an acid a fter the

hydrogen ion (pro ton) is lost.

(2) A conjuga te acid is formed when a hydrogen ion is

transfered to the conjugate base.

(3) Two substances related in this way make up a conjugate

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acid-base pair

(a) eg. Carbonic acid (conjugate acid) and bicarbona te

conjugate base) H2CO3 WH+ + HCO3-

(b) reversible reaction results in an equilbrium.

(4) The conjugated acid base pair can resist changes in pH

because of this equilibrium.

(a) If an acid is added to the buffer? H+ combine with the

base component — the concentration of H+ ions does

not increases as much as it would without this reaction.

(b) If a base is added to the buffer? The conjugate acid

can release H+ which combines w ith the OH- to form

water. The net result is that the H+ ion concetration

stays within a normal range.

(c) The greate r the buffer concentration the more e ffective

it is at resisting changes in the pH.

(d) Important buffers in the body Include: bicarbonate,

phosphates, amino acids, and proteins.

D. Oxygen

1. Another important inorganic molecule is oxygen.

2. Oxygen consists of two oxygen atoms bound by a double covalent

bond.

3. Oxygen is required in the final steps of changing food into usable

energy in our bodies.

E. Carbon dioxide

1. One carbon and two oxygen

2. Produce when organic molecules are metabolized

3. CO2 is eliminated from the cell, travels through the blood and then is

exhausted through the lungs.

4. CO2 accumulation in cells is toxic.

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V. ORGANIC CHEMISTRY

-Organic chemistry is carbon based.

-Carbons ability to form covalent bonds with other atoms makes possible the

formation of large diverse complicated molecules (Carbon forms the backbone of

many large molecules).

-Four major groups of o rganic molecules a re essential to living organisms:

carbohydrates

lipids

proteins

nucleic acids.

A. Carbohydrates

1. Characteristics

a. Composed of carbon, hydrogen, and oxygen

b. range in size from very small (simple sugars) to very large

(polysaccharides)

c. For each carbon there are genera lly 2 H+ and 1 O atom.

d. Carbo - hydrates = carbon + watered

(1) ie because they conta in so much oxygen they are soluble in

water.

2. Monosaccharides

a. Monosaccharides or simple sugars are the building blocks for large

carbohydrates.

(1) Commonly contain 3, 4, 5

or 6 carbons.

(2) Suffix -ose denotes a sugar

molecule

b. Common 6 carbon sugars

(hexose) such as glucose, fructose

and galactose are isomeres

(1) Isomeres are molecules

with the same chemical

formula but differ in the

arrangement of those

chemicals.

(2) Glucose is the major carb

in blood

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(3) Fructose and galactose are found in foods.

(4) Important 5 C sugars include ribose and deoxyribose found in

RNA and DN A. Respectively

3. Disaccharides

a. Composed of two simple

sugars combined through a

dehydra tion synthesis

reaction L(1) Glucose + fructose

= sucrose (tab le

sugar) + water.

(2) Glucose + galactose

= lactose (milk

sugar)

4. Polysaccharides

a. Consist o f many

monosaccharides bound

together to form long chains.

b. These chains are can be either straight or branched

c. Glycogen - composed of many glucose molecules (important storage

molecule.

(1) highly branched

(2) Glucose for muscle contrac tion is generally s tored as glycogen in

the liver or muscle.

d. Starch and cellulose (two other important polysaccharides) found in

plants.

(1) composed of long chains of glucose.

(2) fewer branches than glycogen.

(3) humans have the necessary enzymes to break down s tarch but

lack the enzymes to break down cellulose.

(4) broken down by a hydrolys is reaction.

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B. LIPIDS - the second major group of organic molecules common in living

things.

1. Composed mainly of C, O and H ,

a. like carbohydrates however the proportion of Oxygen is much lower

(1) less polar than carbs

(2) insoluable in water.

(a) soluable in nonpolar organic solvents such as alcohol or

acetone.

b. Lipids differ in chemical structure but are put into the lipid category by

virtue of a common physical property - they are insoluble in water.

c. Phosphorus and nitrogen are also minor components of lipids.

d. Categories of lipids:

(1) Fats

(a) broken down by hydrolysis reactions in the cell to release

energy.

(b) excess chemical energy is stored as fat in the body

(c) fat provides protection and padding of organs, also prevents

heat loss.

(2) LTriacylglycerols (triglycerides)

(a) constitute 95% of the fat in the human body.

(b) made up of glycerol and fatty acids.

(c) Glycerol - three carbon molecule with hydroxyl groups

attached to each

carbon a tom.

i) described according to

the number of fatty

acid chains attatched

to them. –

monoacylglycerol,

diacylglycerols etc.

(d) Fatty acids - straight

chains of carbon atoms

with a carboxyl group

at one end (-COOH)

i) the carboxyl group is responsible for the acidic nature.

ii) differ in the degree of saturation of their carbon chains.

a) Saturated - only single covalent bonds betw een carbons

(beef, pork, butter, eggs, coconut oil contain a high

percentage of saturated fat.)

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b) Unsaturated - one or more double bonds

c) monounsturated - (one double bond) olive oil, peanut oil

d) Polyunsaturated - (two or more double bonds) safflower,

corn, fish -don’t contribute to heart disease.

(3) Phospholipids

(a) Similar to triacyl- glycerols except one fatty acid chain is

replaced by a molecule containing

phosphate and usually nitrogen.

(b) polar at one end

(phosphate end)

and nonpolar at

the other (carbon

chain).

i) polar end-

hydrophilic

ii) nonpolar end -

hydrophobic

(c) Important

component o f cell

membranes

i) Structure allows the formation of micelles and lipid bilayer.

(4) Steroids

(a) 4 ring like structures

i) 3- 6 carbon rings and 1- 5 carbon ring.

(b) non soluble in water and therefore catagorized as lipids.

(c) includes: cholestero l, estrogen, testosterone, progesterone

and bile salts.

(d) Cholesterol is an important because:

i) other stero id molecules are synthesized from it.

ii) component of cell membranes (fluidity).

(e) Sex steroids:

i) important in reproductive behaviors and functions.

ii) Produce secondary sex characteristics.

iii) Testosterone - increases muscle and bone mass

a) side effects - mental problems, bloating face, violent

mood swings, depression, liver damage, increase in blood

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cholesterol leading to serious cardiovascular problems,

reduced sex drive, infertility.

e. Prostiglandins.

(1) fatty acid with a cyclic head group.

(2) Regulatory functions

(a) regulate blood vessel diameter, ovulation, uterine contraction,

inflamation, blood clotting.

C. Proteins - the third major group of organic molecules common in living

things.

1. Biological polymer made up of amino acids.

2. Seven c lasses of Prote ins:

a. Structural

b. Contractile

c. Storage

d. Defensive

e. Transport -

f. Signal -

g. Enzymes -

3. Proteins Contain: carbon, hydrogen, oxygen and nitrogen (some sulfur)-

a.

4. Protein Structure

a. Made up of amino acids.

(1) amino acids contain:

(a) carboxyl group (-COO H) and an amine group (-NH2).

(2) There are 20 different amino acids

(a)

(3) The amino ac ids form long chains held together by peptide

bonds : covalent bond formed by dehydration synthesi

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(4) Proteins are polypeptides composed of hundreds of a.a.

(5) There are 20 different a.a. therefore the potential number of

different protein molecules is enormous.

b. Proteins shape determines its function

(1) Each Proteins molecule has a specific three dimensional shape

determined by its amino acid sequence,

(a) Denaturation -unraveling of protein chain -

i) loss of shape results in loss of function.

c. Proteins can have four different structural levels

(1) Primary structure -

(a)

(2) Secondary structure -

(a)

(b)

(3) Tertiary structure -

(a)

(b)

i) Disulfide bonds:

ii) interaction with water

(c)

(4) Quaternary structure

(a)

(b)

(c)

(d)

D. NUCLEIC ACIDS: DNA and RNA

1. Deoxyribonucleic ac id (DNA)- the genetic materia l of the cell

2. Ribonucleic acid (RNA)

a. Structurally related to DNA

b. Three types

(1)

(2)

(3)

c. Means of translating the gene tic message from DNA to

protein.(Chapter 3)

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3. Nucleic acids

a. Large molecules composed of C H O N P

b. DNA and RNA composed of basic building blocks called Nucleotides.

(1) Figure 2.24

(2)

(3)

(4) The organic bases are:

(a) thymine, cytosine, uracil (single ringed pyrimidines)

(b) guanine and adenine (double ringed purines)

(5) Nucleotides are joined in a chain to form the nucleic acids.

c. DNA

(1)

(2)

(3) Adenine binds only to Thymine - allows 2 hydrogen bonds

(4) Cytosine binds only to guanine - allows 3 hydrogen bonds

(5) chromatin =

(6) Histones =

(7) chromosomes =

d. RNA

(1)

(2)

(3) uracil substitutes for thymine

e. The sequence of organic bases in DNA s tores gene tic information.

(1) The sequence of organic bases in DNA ultimately dicta tes the

sequence of a.a. found in protein molecules.

(2) Because enzymes are prote ins- DNA ultimately determines the

rate and type of chemical reactions in the cell.

E. Adenos ine Triphosphate

1. Consists of adenosine and three phosphate groups. Fig. 2.27

2.

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7. Once produced ATP can be used to provide energy to other chemical

reactions

a. ATP º ADP + P + energy