CHAPTER 6Ground Rules of Metabolism

ENERGY Energy = capacity to do work Potential Energy—stored energy in

resting object Kinetic Energy—energy of motion

THERMODYNAMICS 1st Law of Thermodynamics: Energy

cannot be created or destroyedConverted from one form to another

2nd Law of Thermodynamics: Energy flows from organized to disorganized formsConcentrated energy tends to disperse

spontaneouslyMoves from useable to non-useable energyChemical bonds resist this direction of

energy flow

THERMODYNAMICS Entropy: Measure of randomness or

disorder in a systemOrganized energy = useable = less entropyDisorganized = not useable = more entropy

Living things must maintain ongoing replacement of lost energy

METABOLISM All chemical reactions within a cell or

organism Reactants Products

+ =

CHEMICAL REACTIONS Anabolic

Building reactions (dehydration synthesis)Endergonic—need energyA + B + Energy = CUsually not spontaneous

CatabolicBreaking down reactions (hydrolysis)Exergonic—release energyC = A + B + EnergyUsually spontaneous

CHEMICAL REACTIONS Activation Energy—minimum energy

that can get a reaction to run on it’s own.Cells control energy input into reactions,

therefore controlling timing & speed of reactions.

CHEMICAL REACTIONS Endergonic coupled with exergonic Released energy from one fuels other

C = A +B + Energy

D + E + Energy = F

ATP Energy source for cells Created by photosynthesis or in

mitochondria

ATP

ATP Breaking down ATP releases energy This powers cell fuctions

E.g. Active transport proteins

ENZYMES Biological catalysts

Speed up chemical reactionsDon’t start reactions on their own

Reusable Can catalyze in forward & reverse Very specific!

Substrate attaches to enzyme’s active site

ENZYMES Lowers activation energy

Makes reactions faster & easier

CONTROLS OVER ENZYMES Concentration

EnzymesReactantsProducts

Temperature pH Enzyme cofactors

vitamins

CONTROLS OVER ENZYMES Inhibition

Competitive—binds to site first or more strongly

Non-competitive—binds to different area, changing enzyme bonding area

CONTROLS OVER ENZYMES Feedback inhibition

Product of reaction binds to allosteric siteShuts down reaction