The Chemistry of LifeThe Chemistry of Life

Chapter 2Chapter 2

Periodic Table of the ElementsPeriodic Table of the Elements

WaterWater

Water is polar = Water is polar = uneven distribution uneven distribution of chargeof charge Oxygen “pulls” on Oxygen “pulls” on

hydrogens’ hydrogens’ electronselectrons

Oxygen is more Oxygen is more negative, negative, hydrogens are hydrogens are more positivemore positive

Hydrogen Bonding of WaterHydrogen Bonding of Water

Polarity of water Polarity of water leads to hydrogen leads to hydrogen bonding between bonding between water moleculeswater molecules

Negative oxygens Negative oxygens are attracted to are attracted to positive hydrogenspositive hydrogens

MixturesMixtures

Solution – a substance is evenly dissolved Solution – a substance is evenly dissolved in a liquidin a liquid Ex – salt water: salt is the solute, water is the Ex – salt water: salt is the solute, water is the

solventsolvent Water is the strongest solvent known because Water is the strongest solvent known because

it is polarit is polar Blood is a solution Blood is a solution

http://xeon.concord.org:8080/modeler/webstart/http://xeon.concord.org:8080/modeler/webstart/solution/dissolve.jnlpsolution/dissolve.jnlp

MixturesMixtures

Suspension – a substance is distributed, Suspension – a substance is distributed, not dissolved, in waternot dissolved, in water Ex – blood contains cells which are Ex – blood contains cells which are

suspended in plasmasuspended in plasma

pH Scale (0-14)pH Scale (0-14)

Measures concentration of HMeasures concentration of H++ in solution in solution

HH22O O ↔ H↔ H++ + OH + OH--

waterwater ↔ hydrogen ion + hydroxide ion↔ hydrogen ion + hydroxide ion

More HMore H++ = lower pH = more acidic = lower pH = more acidic More OHMore OH-- = higher pH = more basic = higher pH = more basic When [HWhen [H++] = [OH] = [OH--], solution is neutral, pH = 7], solution is neutral, pH = 7

pH ScalepH Scale

↑ H+

↑ OH-

pH ScalepH Scale

Acids produce HAcids produce H++ when dissolved in water when dissolved in water HCl (hydrochloric acid) stomach acidHCl (hydrochloric acid) stomach acid

Bases produce OHBases produce OH- - when dissolved in when dissolved in waterwater NaOH (sodium hydroxide) found in bleachNaOH (sodium hydroxide) found in bleach

CarbonCarbon

Carbon (C) can make four covalent bondsCarbon (C) can make four covalent bonds Provides a variety of structurally different Provides a variety of structurally different

moleculesmolecules C forms theC forms the

backbone of allbackbone of allbiological moleculesbiological molecules

Molecules that Molecules that contain C calledcontain C calledorganicorganic

Biological MoleculesBiological Molecules

All biological molecules are large All biological molecules are large molecules (macromolecules or polymers) molecules (macromolecules or polymers) composed of smaller molecules composed of smaller molecules (monomers)(monomers)

Four classes:Four classes: CarbohydratesCarbohydrates LipidsLipids ProteinsProteins Nucleic AcidsNucleic Acids

CarbohydratesCarbohydrates

Carbo-: carbonCarbo-: carbon-hydrate: water, H-hydrate: water, H22OO

Major energy sourceMajor energy source MonosaccharidesMonosaccharides

Single sugarSingle sugar Ex – glucose, fructoseEx – glucose, fructose Monomers for larger Monomers for larger

carbohydratescarbohydrates

CarbohydratesCarbohydrates

DisaccharidesDisaccharides Two sugarsTwo sugars Ex – Sucrose (table sugar), lactose (milk)Ex – Sucrose (table sugar), lactose (milk)

PolysaccharidesPolysaccharides Many sugars chained togetherMany sugars chained together

ExamplesExamples Animals store sugar as Animals store sugar as glycogenglycogen Plants store sugar as Plants store sugar as starchstarch Plant cell walls made of Plant cell walls made of cellulosecellulose

LipidsLipids

Fats, oils, waxes and Fats, oils, waxes and steroidssteroids

Stored energy Stored energy reservesreserves

Saturated fats – solid Saturated fats – solid at room temp.at room temp.

Unsaturated fats – Unsaturated fats – liquid at room temp.liquid at room temp.

ProteinsProteins Important in growth, repair and chemical Important in growth, repair and chemical

reactionsreactions Made of amino acids (monomers)Made of amino acids (monomers)

20 different aa in humans20 different aa in humans aa joined by peptide bondsaa joined by peptide bonds

AKA – AKA – polypeptides polypeptides (many amino (many amino acids)acids)

Amino acidsPeptide bond

ProteinsProteins

Aminoacids

Nucleic AcidsNucleic Acids

DNA – DNA – ddeoxyriboeoxyribonnucleic ucleic aacidcid RNA – RNA – rriboibonnucleic ucleic aacidcid Most complex biological Most complex biological

moleculemolecule Control heredityControl heredity Polymer of nucleotidesPolymer of nucleotides

5 nucleotides in humans5 nucleotides in humansDNA

Chemical ReactionsChemical Reactions

A reaction occurs when chemical bonds A reaction occurs when chemical bonds are broken or formedare broken or formed

If the reaction releases energy, it will occur If the reaction releases energy, it will occur spontaneouslyspontaneously

If the reaction requires energy, it needs an If the reaction requires energy, it needs an input of energy to occurinput of energy to occur Heat, stirringHeat, stirring Activation energyActivation energy is the energy needed to is the energy needed to

start reactionstart reaction

Cellular ReactionsCellular Reactions

Heat Heat necessary to necessary to start reactions start reactions in cells would in cells would kill cellskill cells

Cells must Cells must lower lower activation activation energyenergy

EnzymesEnzymes

Proteins that lower the activation energy of Proteins that lower the activation energy of reactionsreactions

Act as a catalystAct as a catalyst Are not changed or consumed by the Are not changed or consumed by the

reactionreaction Specific to each substrate (substance Specific to each substrate (substance

enzyme “helps” to react)enzyme “helps” to react)

EnzymesEnzymes

Lock and key hypothesisLock and key hypothesis Active site on enzyme and substrate fit Active site on enzyme and substrate fit

together like a lock and keytogether like a lock and key Temperature and pH affect enzyme Temperature and pH affect enzyme

activityactivity