chemistry of anatomy and physiology. atoms smallest unit of an element subatomic particles protons:...

Chemistry of Anatomy and Physiology

AtomsSmallest unit of an

elementSubatomic particles

Protons: (+) chargeNeutrons: neutralElectrons: (-) charge

AtomsSmallest unit of an

elementSubatomic particles

Protons: (+) chargeNeutrons: neutralElectrons: (-) charge

Figure 2-1

•Structure of an atomNucleus

Protons Neutrons

Electron Cloud

•Structure of an atomNucleus

Protons Neutrons

Electron Cloud

Figure 2-2(b)

Structure of atomAtomic number

Equals number of protonsAtomic mass

Equals protons + neutronsIsotopes of element

Reflects number of neutronsAtomic weight

Averages isotope abundance

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

• Structure of atomElectrons surround nucleusElectrons organized in shells

(sublevels)The outer shell determines

chemical properties


Key NoteAll matter is composed of atoms in various combinations. Their interactions establish the foundations of physiology at the cellular level.


Chemical Bonds and CompoundsAtoms bond in chemical reactionsElectrons are gained, lost, or sharedMolecules or compounds resultCompounds contain several elements


Ionic BondsAtoms gain or lose electronsCharged atoms are ionsIons bear (+) or (-) charge

Cations have (+) chargeAnions have (-) charge

Cations and anions attractIons form bonds


Table 2-2

Covalent bondsSome atoms share electronsShared electrons complete outer shell Sharing atoms bond covalently

Single covalent bondOne shared electron

Double covalent bondTwo shared electrons


Figure 2-5

Nonpolar and Polar Covalent BondsEqual electron sharing

Nonpolar covalent bondsExample: carbon-carbon bonds

Non-equal electron sharingPolar covalent bondsExample: oxygen-hydrogen bonds


Hydrogen bondsWeak attractive forceBetween 2 neighboring atoms

A polar-bonded hydrogen, andA polar-bonded oxygen or nitrogen

For example, between water molecules


Figure 2-6

A chemical “shorthand”Simplified descriptions of:

CompoundsStructuresReactionsIons

Abbreviations of elementsAbbreviations of molecules


Basic Energy ConceptsWork—movement or change in

matter’s physical structureE.g., running, synthesis

Energy—ability to do workKinetic energyPotential energy


Basic Energy Concepts (continued)Potential energy—stored energy

E.g., leopard lurks in a treeKinetic energy—energy of movement

E.g., leopard pounces on prey


3 types of reactionsDecomposition—breaks molecule

into smaller piecesSynthesis—assembles smaller

pieces into larger oneExchange—shuffles pieces

between molecules


Decomposition ReactionsIn chemical notation:

AB A + BReleases covalent bond energy

Hydrolysis—Decomposition reaction with H•OHE.g., food digestion

Catabolism—Sum of all the body’s decomposition reactions


Synthesis ReactionsIn chemical notation:

A + B ABAbsorbs energy

Formation of new bondsDehydration synthesis

Removal of H•OH between moleculesAnabolism—Sum of the body’s synthesis

reactions

Exchange ReactionIn chemical notation:

AB + CD AC + BDDecomposition and synthesis


Reversible ReactionsA + B ABEquilibrium—Condition when

the forward and reverse reactions occur at the same rate

Exergonic—Reactions that release energyE.g., decomposition reactions

Endergonic—Reactions that consume energyE.g., synthesis reactions


Key TermsNutrients

Essential elements and molecules obtained from the diet

MetabolitesMolecules synthesized or broken down by

chemical reactions inside the body


InorganicSmaller molecules such as water and

oxygen that lack carbon and hydrogen

OrganicLarger molecules such as sugars,

proteins, and fats composed largely of carbon and hydrogen


Carbon Dioxide (CO2)Gas produced by cellular

metabolism and released into the atmosphere via the lungs

Oxygen (O2)Atmospheric gas consumed by cells

in order to produce energy


Water and its propertiesMost important body chemicalExcellent solventHigh heat capacityEssential chemical reactant


Key Note Water accounts for most of your body weight. Proteins, key components of cells, and nucleic acids, which control cells, work only in solution.


pHA measure of hydrogen ion

concentration in a solution

Neutral solution—pH = 7Acidic solution—pH below 7Basic solution—pH above 7


Figure 2-9

BuffersMaintain pH within normal

limits (pH 7.35 to pH 7.45)Release hydrogen ions if body

fluid is too basicAbsorb hydrogen ions if body

fluid is too acidic


Organic CompoundsContain carbon, hydrogen, and

usually oxygenImportant classes of organic

compounds include:CarbohydratesLipidsProteinsNucleic acids


CarbohydratesMost important energy source for

metabolismThree major types

Monosaccharides (E.g., glucose)Disaccharides (E.g., sucrose)Polysaccharides (E.g., glycogen)


Figure 2-10

LipidsWater-insolubleFour important classes

Fatty acidsFatsSteroidsPhospholipids


ProteinsMost abundant organic component

in human bodyAbout 100,000 different proteinsContain carbon, nitrogen, oxygen,

hydrogen, and a bit of sulfur


Proteins play vital rolesSupportMovementTransportBufferingRegulationDefense


•Peptide bonds join amino acids into long strings

Protein Structure“R” groups interact with their

neighbors and with solventAmino acid chain folds and

twists into complex shapeFinal shape determines functionHigh fever distorts shapeDistorted proteins don’t work


Enzyme FunctionSubstrates (reactants) bind to

active site on enzyme surfaceBinding lowers activation energy

needed for reactionSubstrates react to form productProduct is released from enzyme

surface


Figure 2-18

Nucleic AcidsLarge moleculesBuilt from atoms of C, H, O, N, and P

(What are these elements?)Store and process molecular informationTwo classes of nucleic acid

DNA (deoxyribonucleic acid)RNA (ribonucleic acid)


Structure of Nucleic AcidsNucleotides contain a sugar, a

phosphate, and a baseSugar-phosphate bonds link

nucleotides in long strandsHydrogen bonds hold two DNA

strands in a double helix


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