Energy and Energy and EnzymesEnzymes

How do the right chemical How do the right chemical reactions happen in the right reactions happen in the right

place at the right time?place at the right time?A.P. BiologyA.P. Biology

EnergyEnergy MetabolismMetabolism

- All the chemical reactions in a cell- All the chemical reactions in a cell

CatabolismCatabolism – breaking reactions – breaking reactions AnabolismAnabolism – making reactions – making reactions

All chemical reactions need energyAll chemical reactions need energy EnergyEnergy – the ability to do work – the ability to do work

Muscle contraction, chemical reactions, Muscle contraction, chemical reactions, intracellular transport, active transportintracellular transport, active transport

Types of EnergyTypes of Energy

KineticKinetic Free Energy – energy available to do Free Energy – energy available to do

workwork

PotentialPotential Chemical Energy – energy stored in Chemical Energy – energy stored in

organic moleculesorganic molecules

Laws of ThermodynamicsLaws of Thermodynamics Law of Conservation of EnergyLaw of Conservation of Energy

Energy is never created or destroyedEnergy is never created or destroyed Living things need an energy sourceLiving things need an energy source

Law of EntropyLaw of Entropy Energy transfer makes the universe Energy transfer makes the universe

more disorderedmore disordered As energy is transferred from chemical to As energy is transferred from chemical to

free energy – a lot is lost as heatfree energy – a lot is lost as heat Living things need to use a lot of energy to Living things need to use a lot of energy to

stay orderedstay ordered

Free Energy – energy Free Energy – energy available to do workavailable to do work

G(free/usable energy) = H (total G(free/usable energy) = H (total energy) – TS (entropy)energy) – TS (entropy)

Energy converted to heat isn’t Energy converted to heat isn’t available to do work.available to do work.

Exergonic – catabolic – breaking – Exergonic – catabolic – breaking – energy releasingenergy releasing

Endergonic – anabolic – making – Endergonic – anabolic – making – energy absorbing – energy is now energy absorbing – energy is now stored in the molecules madestored in the molecules made

CouplingCoupling

Energy from exergonic reactions are Energy from exergonic reactions are used to power endergonic reactionsused to power endergonic reactions

Breaking carbs is exergonic – used to Breaking carbs is exergonic – used to make ATP – endergonic (energy make ATP – endergonic (energy stored in ATP)stored in ATP)

ATP is broken down to power ATP is broken down to power chemical reactions, muscle chemical reactions, muscle contractions, etc. – exothermiccontractions, etc. – exothermic

A cell can make 10 million ATP/sec.A cell can make 10 million ATP/sec.

EnzymesEnzymes Enzymes lower the activation energy for Enzymes lower the activation energy for

a chemical reaction so it can happen a chemical reaction so it can happen with less energywith less energy

One enzyme can convert 1000 One enzyme can convert 1000 molecules/sec.molecules/sec.

Enzymes control Enzymes control whatwhat chemical chemical reactions happen reactions happen wherewhere and and how fasthow fast in in the body so they generally run the body.the body so they generally run the body.

Enzymatic Anabolic Enzymatic Anabolic ReactionsReactions

Enzymatic Catabolic Enzymatic Catabolic ReactionReaction

Possible Ways Enzymes Possible Ways Enzymes Lower The Activation Lower The Activation Energy of a Chemical Energy of a Chemical

ReactionReaction Bring substrates together and squeezes them Bring substrates together and squeezes them (takes less energy to form a bond) - anabolic(takes less energy to form a bond) - anabolic

Substrate binds – changes shape of the Substrate binds – changes shape of the enzyme – enzyme squeezes substrate enzyme – enzyme squeezes substrate straining the bonds (need less energy to straining the bonds (need less energy to break bonds) - catabolicbreak bonds) - catabolic

pH of active site may be highly acidic due to pH of active site may be highly acidic due to the R groups there (helps break bonds) - the R groups there (helps break bonds) - cataboliccatabolic

Enzyme may actually bond to substrate Enzyme may actually bond to substrate causing shape changes in the substrate causing shape changes in the substrate which makes it easier to break the bonds in which makes it easier to break the bonds in the substratethe substrate

Things that Effect Enzyme Things that Effect Enzyme Rate of ReactionRate of Reaction

TemperatureTemperature At low temperatures, enzymes and substrates At low temperatures, enzymes and substrates

move slower – less collisions – slower reactionmove slower – less collisions – slower reaction As temperature increases – more collisions – As temperature increases – more collisions –

faster rate of reaction until the temp. is too faster rate of reaction until the temp. is too high and the enzyme denatures – rate drops high and the enzyme denatures – rate drops to 0to 0

pHpH All enzymes work best at an optimal pH, if All enzymes work best at an optimal pH, if

that pH changes in either direction, enzymes that pH changes in either direction, enzymes denaturedenature

Things that Effect Things that Effect Enzymatic RatesEnzymatic Rates

Enzyme concentration (amt./vol.)Enzyme concentration (amt./vol.) Higher the concentration, faster the rate of Higher the concentration, faster the rate of

reactionreaction but even starting with excess substrate, but even starting with excess substrate,

the substrate will run out as enzyme conc. the substrate will run out as enzyme conc. increases the rate will level offincreases the rate will level off

Substrate ConcentrationSubstrate Concentration As sub. conc. increases, act. increases As sub. conc. increases, act. increases Levels off as eventually every enzyme is Levels off as eventually every enzyme is

busy and it can’t go any fasterbusy and it can’t go any faster

Things that Effect…Things that Effect…

Presence of InhibitorsPresence of Inhibitors CompetitiveCompetitive Non-competitive (allosteric)Non-competitive (allosteric)

Lab and Artificial Uses of InhibitorsLab and Artificial Uses of Inhibitors PoisonsPoisons Drugs that interfer with enzymes in Drugs that interfer with enzymes in

pathogens (antibiotics)pathogens (antibiotics)

How the body manipulates How the body manipulates enzymes to control enzymes to control chemical reactionschemical reactions

Keep a steady amount of Keep a steady amount of ProductProduct Feedback InhibitionFeedback Inhibition

the product of a multi-step pathway the product of a multi-step pathway allosterically inhibits an earlier step in the allosterically inhibits an earlier step in the pathwaypathway

Substrates turn enzymesSubstrates turn enzymes on by allosteric on by allosteric activation and activation and products turn off enzymesproducts turn off enzymes by allosteric inhibition – (Example: ATP by allosteric inhibition – (Example: ATP and ADP on a glycolysis enzyme)and ADP on a glycolysis enzyme)

How the body manipulates How the body manipulates enzymes to control enzymes to control chemical reactionschemical reactions Optimize Reactions that must Optimize Reactions that must

happen efficiently all the timehappen efficiently all the time Spatial ControlSpatial Control – some enzymes are embedded – some enzymes are embedded

in a membrane and cannot move relative to in a membrane and cannot move relative to other enzymes – therefore enzymes involved in a other enzymes – therefore enzymes involved in a step-wise reaction can happen quickly and in step-wise reaction can happen quickly and in orderorder

Compartmentalization - sCompartmentalization - some enzymes are ome enzymes are kept in small inside an organelle where kept in small inside an organelle where reactions can happen more quicklyreactions can happen more quickly

Can also include keeping the pH and Can also include keeping the pH and temperature optimaltemperature optimal

How the body optimizes reactions How the body optimizes reactions continuedcontinued

CooperativityCooperativity used only in multi-subunit enzymes used only in multi-subunit enzymes binding of a substrate causes a conformational binding of a substrate causes a conformational

change in the enzyme (induced fit) that allows other change in the enzyme (induced fit) that allows other substrates to bind faster substrates to bind faster

more substrate present – faster the enzyme worksmore substrate present – faster the enzyme works Maximizes reaction with a small amount of substrateMaximizes reaction with a small amount of substrate

Coenzymes and CofactorsCoenzymes and Cofactors – necessary in – necessary in many cases to make the active site the right shape for many cases to make the active site the right shape for the substratethe substrate

Coenzymes – organic – usually vitaminsCoenzymes – organic – usually vitamins Cofactors – inorganic such as Mg, Zn, etc.Cofactors – inorganic such as Mg, Zn, etc. Enzymes can be controlled by the availability of Enzymes can be controlled by the availability of

coenyzmes and cofactorscoenyzmes and cofactors

How the body manipulates How the body manipulates enzymes to control enzymes to control chemical reactionschemical reactions

Make the Product Only When NeededMake the Product Only When Needed Protein SynthesisProtein Synthesis – If don’t want to waste – If don’t want to waste

energy making enzymes not needed and when energy making enzymes not needed and when needed - not needed fast – can make them from needed - not needed fast – can make them from scratchscratch

The presence of certain substrates can turn on The presence of certain substrates can turn on protein synthesis or products can shut down protein synthesis or products can shut down protein synthesis at the DNA levelprotein synthesis at the DNA level

A messenger can signal the cell to make enzymesA messenger can signal the cell to make enzymes

CompartmentalizationCompartmentalization - - Some enzymes are Some enzymes are sequestered and released only at certain sequestered and released only at certain times (example amylase and pepsin)times (example amylase and pepsin)

Make the Product Only When Make the Product Only When NeededNeeded Cleavage of EnzymeCleavage of Enzyme – enzymes are formed in – enzymes are formed in

an inactive form and then cleaved when an inactive form and then cleaved when needed to make the right shape (thrombin, needed to make the right shape (thrombin, pepsin)pepsin)

PhosphorylationPhosphorylation – adding phosphates to – adding phosphates to change the shape and activate or inactivate change the shape and activate or inactivate enzymesenzymes

pHpH –is varied in some organs to control –is varied in some organs to control enzyme action – make it the right pH to enzyme action – make it the right pH to activate enzymes and the wrong pH to activate enzymes and the wrong pH to inactivate them (stomach and small intestine)inactivate them (stomach and small intestine)