Chapter 6 Powerpoint Le

MetabolismChapter 06

2MetabolismMetabolism

OutlineOutline

Forms of EnergyForms of EnergyLaws of ThermodynamicsLaws of Thermodynamics

Metabolic ReactionsMetabolic ReactionsATPATP

Metabolic PathwaysMetabolic PathwaysEnergy of ActivationEnergy of ActivationEnzymesEnzymesPhotosynthesisPhotosynthesisCellular RespirationCellular Respiration


Forms of EnergyForms of Energy

KineticKinetic::

Energy of motionEnergy of motion

MechanicalMechanical

PotentialPotential::

Stored energyStored energy

ChemicalChemical

4Flow of Energy


Laws of ThermodynamicsLaws of Thermodynamics

First law:First law:Law of Law of conservation of energyconservation of energyEnergy cannot be created or destroyed, butEnergy cannot be created or destroyed, butEnergy CAN be changed from one form to Energy CAN be changed from one form to anotheranother

Second law:Second law:Law of Law of entropyentropyWhen energy is changed from one form to When energy is changed from one form to another, there is a loss of usable energyanother, there is a loss of usable energy

Waste energy goes to increase disorderWaste energy goes to increase disorder

6Carbohydrate Synthesis

7Carbohydrate Metabolism

8Cells and Energy

9MetabolismMetabolismMetabolic Reactions andMetabolic Reactions andEnergy TransformationsEnergy Transformations

MetabolismMetabolism::

Sum of cellular chemical reactions in cellSum of cellular chemical reactions in cell

ReactantsReactants participate in reaction participate in reaction

ProductsProducts form as result of reaction form as result of reaction

Free energyFree energy is the amount of energy available is the amount of energy available to perform workto perform work

Exergonic ReactionsExergonic Reactions - Products have - Products have lessless free free energy than reactants energy than reactants

Endergonic ReactionsEndergonic Reactions - Products have - Products have moremore free energy than reactantsfree energy than reactants


ATP and Coupled ReactionsATP and Coupled Reactions

Adenosine triphosphateAdenosine triphosphate ( (ATPATP))High energy compound used to drive High energy compound used to drive metabolic reactionsmetabolic reactions

Constantly being generated from adenosine Constantly being generated from adenosine diphosphate (diphosphate (ADPADP))

Composed of:Composed of:AdenineAdenine and and riboseribose (together = (together = adenosineadenosine), ), andand

Three phosphate groupsThree phosphate groupsCoupled reactionsCoupled reactions

Energy released by an exergonic reaction Energy released by an exergonic reaction captured in ATPcaptured in ATP

That ATP used to drive an endergonic reactionThat ATP used to drive an endergonic reaction

11The ATP Cycle

12Coupled Reactions

Figure 6.4

13MetabolismMetabolismMetabolic Reactions andMetabolic Reactions andEnergy TransformationsEnergy Transformations

MetabolismMetabolism::

Sum of cellular chemical reactions in cellSum of cellular chemical reactions in cell

ReactantsReactants participate in reaction participate in reaction

ProductsProducts form as result of reaction form as result of reaction

Free energyFree energy is the amount of energy available is the amount of energy available to perform workto perform work

Exergonic ReactionsExergonic Reactions - Products have - Products have lessless free free energy than reactants energy than reactants

Endergonic ReactionsEndergonic Reactions - Products have - Products have moremore free energy than reactantsfree energy than reactants

14MetabolismMetabolismWork-Related FunctionsWork-Related Functionsof ATPof ATP

Primarily to perform cellular workPrimarily to perform cellular work

Chemical Work - Energy needed to synthesize Chemical Work - Energy needed to synthesize macromoleculesmacromolecules

Transport Work - Energy needed to pump Transport Work - Energy needed to pump substances across plasma membranesubstances across plasma membrane

Mechanical Work - Energy needed to contract Mechanical Work - Energy needed to contract muscles, beat flagella, etcmuscles, beat flagella, etc


Metabolic PathwaysMetabolic Pathways

Reactions are usually occur in a sequenceReactions are usually occur in a sequenceProducts of an earlier reaction become Products of an earlier reaction become reactants of a later reactionreactants of a later reaction

Such linked reactions form a Such linked reactions form a metabolic metabolic pathwaypathway

Begins with a particular Begins with a particular reactantreactant,,

Proceeds through several Proceeds through several intermediatesintermediates, and, and

Terminates with a particular Terminates with a particular end productend product

AB C D E FG“A” is Initial

Reactant“G” is End

ProductIntermediates


EnzymesEnzymes

EnzymesEnzymesProtein molecules that function as catalystsProtein molecules that function as catalystsThe reactants of an enzymatically accelerated The reactants of an enzymatically accelerated reaction are called reaction are called substratessubstrates

Each enzyme accelerates a specific reactionEach enzyme accelerates a specific reactionEach reaction in a metabolic pathway requires Each reaction in a metabolic pathway requires a unique and specific enzymea unique and specific enzyme

End product will not appear unless ALL End product will not appear unless ALL enzymes present and functionalenzymes present and functional

E1 E2 E3 E4 E5 E6A B C D E F G

17MetabolismMetabolismEnzymes:Enzymes:Energy of ActivationEnergy of Activation

Reactants often “reluctant” to participate in Reactants often “reluctant” to participate in reactionreaction

Energy must be added to at least one reactant Energy must be added to at least one reactant to initiate the reactionto initiate the reaction

Energy of activationEnergy of activation

Enzyme Operation:Enzyme Operation:

Enzymes operate by lowering the energy of Enzymes operate by lowering the energy of activationactivation

Accomplished by bringing the substrates into Accomplished by bringing the substrates into contact with one anothercontact with one another

18Energy of Activation


Enzyme-Substrate ComplexEnzyme-Substrate Complex

The The active siteactive site complexes with the substrates complexes with the substrates

Causes active site to change shapeCauses active site to change shape

Shape change forces substrates together, Shape change forces substrates together, initiating bondinitiating bond

Induced fit modelInduced fit model

20Induced Fit Model


Degradation vs. SynthesisDegradation vs. Synthesis

DegradationDegradation::

Enzyme complexes with a single substrate Enzyme complexes with a single substrate moleculemolecule

Substrate is broken apart into two product Substrate is broken apart into two product moleculesmolecules

SynthesisSynthesis::

Enzyme complexes with two substrate Enzyme complexes with two substrate moleculesmolecules

Substrates are joined together and released Substrates are joined together and released as single product moleculeas single product molecule

22Degradation vs. Synthesis


Factors Affecting Enzyme Activity (1)Factors Affecting Enzyme Activity (1)

Substrate concentrationSubstrate concentrationEnzyme activity increases with substrate Enzyme activity increases with substrate concentrationconcentration

More collisions between substrate molecules More collisions between substrate molecules and the enzymeand the enzyme

TemperatureTemperatureEnzyme activity increases with temperatureEnzyme activity increases with temperatureWarmer temperatures cause more effective Warmer temperatures cause more effective collisions between enzyme and substratecollisions between enzyme and substrate

However, hot temperatures destroy enzymeHowever, hot temperatures destroy enzymepHpH

Most enzymes are optimized for a particular Most enzymes are optimized for a particular pHpH

24Factors Affecting Enzyme Activity:Temperature

25Factors Affecting Enzyme Activity:pH



Cells can affect presence/absence of enzymeCells can affect presence/absence of enzyme

Cells can affect concentration of enzymeCells can affect concentration of enzyme

Cells can activate or deactivate enzymeCells can activate or deactivate enzyme

Enzyme Enzyme CofactorsCofactors

Molecules required to activate enzymeMolecules required to activate enzyme

CoenzymesCoenzymes are organic cofactors, like some are organic cofactors, like some vitaminsvitamins

PhosphorylationPhosphorylation – some require addition of a – some require addition of a phosphatephosphate

27Factors Affecting Enzyme Activity:Activation by Phosphorylation



Reversible Reversible enzyme inhibitionenzyme inhibition

When a substance known as an inhibitor binds to an enzyme and decreases its activity

Competitive inhibitioninhibition – substrate and the – substrate and the inhibitor are both able to bind to inhibitor are both able to bind to active siteactive site

Noncompetitive inhibitionNoncompetitive inhibition – the inhibitor binds – the inhibitor binds not at the active site, but at the not at the active site, but at the allosteric siteallosteric site

Feedback inhibitionFeedback inhibition – The end product of a – The end product of a pathway inhibits the pathway’s first enzymepathway inhibits the pathway’s first enzyme

29Factors Affecting Enzyme Activity:Feedback Inhibition


Irreversible InhibitionIrreversible Inhibition

Materials that irreversibly inhibit an enzyme Materials that irreversibly inhibit an enzyme are known as are known as poisonspoisons

CyanidesCyanides inhibit enzymes resulting in all ATP inhibit enzymes resulting in all ATP productionproduction

PenicillinPenicillin inhibits an enzyme unique to certain inhibits an enzyme unique to certain bacteriabacteria

Heavy metalsHeavy metals irreversibly bind with many irreversibly bind with many enzymesenzymes

Nerve gasNerve gas irreversibly inhibits enzymes irreversibly inhibits enzymes required by nervous systemrequired by nervous system


Oxidation-ReductionOxidation-Reduction

Oxidation-reductionOxidation-reduction ( (redoxredox)) reactions: reactions:

Electrons pass from one molecule to anotherElectrons pass from one molecule to another

The molecule that loses an electron is The molecule that loses an electron is oxidizedoxidized

The molecule that gains an electron is The molecule that gains an electron is reducedreduced

Both take place at same timeBoth take place at same time

One molecule accepts the electron given up One molecule accepts the electron given up by the otherby the other

32Photosynthesis andPhotosynthesis andCellular RespirationCellular Respiration

Carbon dioxideCarbon dioxide+water+water+solar energy+solar energy

GlucoseGlucose+oxygen+oxygen

6CO6CO22 + 6H + 6H22OOenergyenergy

CC66HH1212OO66 + 6O + 6O22

Carbon dioxideCarbon dioxide+water+water+chemical energy+chemical energy

GlucoseGlucose+oxygen+oxygen

6CO6CO22 + 6H + 6H22OOCC66HH1212OO66 + 6O + 6O22

Cellular Respiration:Cellular Respiration:

Photosynthesis:Photosynthesis:


Electron Transport ChainElectron Transport Chain

Membrane-bound carrier proteins found in Membrane-bound carrier proteins found in mitochondria and chloroplastsmitochondria and chloroplasts

Physically arranged in an ordered seriesPhysically arranged in an ordered series Starts with high-energy electrons and low-energy Starts with high-energy electrons and low-energy

ADPADP

Pass electrons from one carrier to anotherPass electrons from one carrier to another

Electron energy used to pump hydrogen ions (HElectron energy used to pump hydrogen ions (H++) to ) to one side of membraneone side of membrane

Establishes electrical gradient across membraneEstablishes electrical gradient across membrane

Electrical gradient used to make ATP from ADP – Electrical gradient used to make ATP from ADP – ChemiosmosisChemiosmosis

Ends with low-energy electrons and high-energy ATPEnds with low-energy electrons and high-energy ATP

34A Metaphor for theElectron Transport Chain

35Chemiosmosis


ReviewReview

Forms of EnergyForms of EnergyLaws of ThermodynamicsLaws of Thermodynamics

Metabolic ReactionsMetabolic ReactionsATPATP

Metabolic PathwaysMetabolic PathwaysEnergy of ActivationEnergy of Activation

EnzymesEnzymes

PhotosynthesisPhotosynthesis

Cellular RespirationCellular Respiration

MetabolismEnding Slide Chapter 06

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