Cell Physiology: Cell Physiology: MetabolismMetabolism

Biology 211 Biology 211 Anatomy & Physiology 1Anatomy & Physiology 1

Dr. Tony SerinoDr. Tony Serino

MetabolismMetabolism

Refers to all of the reactions that Refers to all of the reactions that occur in the celloccur in the cell

Each reactions requires a specific Each reactions requires a specific enzymeenzyme

Energy may be released or Energy may be released or consumed in the reactionsconsumed in the reactions

Energy Flow in ReactionsEnergy Flow in Reactions

Metabolic Reactions (R Metabolic Reactions (R P)P)

Most reactions are reversibleMost reactions are reversible All reactions try to proceed to a All reactions try to proceed to a

dynamic equilibrium. Therefore, dynamic equilibrium. Therefore, one way to favor a reaction is to one way to favor a reaction is to manipulate the amount of manipulate the amount of reactants or products present.reactants or products present.

A + B C + D

Metabolic PathwaysMetabolic Pathways

A series of reactions in the body.A series of reactions in the body. Most are linked with other sets, so Most are linked with other sets, so

that the products of one reaction that the products of one reaction become the reactants of the next.become the reactants of the next.

Two Kinds:Two Kinds: Degradative (Catabolism)Degradative (Catabolism) Biosynthetic (Anabolism)Biosynthetic (Anabolism)

Pathway Map of Pathway Map of

Cell MetabolismCell Metabolism

Note: Kreb Cycle

EnzymesEnzymes Catalyze reactionsCatalyze reactions Reactants = substrates (S)Reactants = substrates (S) S bind to active site on ES bind to active site on E S bound non-covalentlyS bound non-covalently 3D structure give E specificity3D structure give E specificity # of bonds formed gives # of bonds formed gives

affinityaffinity May use co-factors (co-May use co-factors (co-

enzymes)enzymes) May bind other chemicals that May bind other chemicals that

act as modulators (change 3D act as modulators (change 3D shape of active site)shape of active site)

Active Site

Substrate

The enzyme’s 3D shape allows it to bind to a specific substrate.

Energy flow in a reactionEnergy flow in a reaction Every Every

reactions reactions must must overcome overcome an energy an energy barrier to barrier to begin. begin.

Energy of Energy of Activation Activation (E(EAA))

Energy Flow with Enzyme Energy Flow with Enzyme PresentPresent

Enzymes Enzymes increase increase reaction reaction rates by rates by lowering lowering the Ethe EAA

Enzymes Lower EEnzymes Lower EAA

Bring reactants into close proximityBring reactants into close proximity Produce bond strain in substratesProduce bond strain in substrates

Both of these characteristics allows the enzyme to lower the reaction’s EA

Control of Enzyme Control of Enzyme FunctionFunction

Proteins Proteins remain remain functional in functional in a narrow a narrow range of pH range of pH and temp.and temp.

Radical Radical changes in changes in these values these values can cause can cause proteins to proteins to denature; denature; that is, that is, change its 3D change its 3D shapeshape

Enzyme Enzyme ControlControl

Enzyme activity Enzyme activity can be modified can be modified by changes in by changes in both enzyme and both enzyme and substrate substrate concentrationsconcentrations

Excess substrate Excess substrate eventually hits a eventually hits a maximum or maximum or saturation pointsaturation point

Enzyme Enzyme ControlControl Other substances may bind Other substances may bind

to the enzyme and modify to the enzyme and modify its behavior; either as an its behavior; either as an activator or inhibitoractivator or inhibitor

If the substance competes If the substance competes with the substrate for the with the substrate for the active site; it is a active site; it is a competitive inhibitorcompetitive inhibitor

If it binds elsewhere and If it binds elsewhere and changes the enzymes changes the enzymes shape at its active site shape at its active site then it is a noncompetitive then it is a noncompetitive inhibitor/activatorinhibitor/activator

Enzyme Modulation:Enzyme Modulation:non-competitive inhibition and non-competitive inhibition and activationactivation

Binding of a molecule to a site other than the active Binding of a molecule to a site other than the active site may result in an enzyme conformational change site may result in an enzyme conformational change that either turns the enzyme “on or off”that either turns the enzyme “on or off”

If the modulator is bound by non-covalent forces; it is If the modulator is bound by non-covalent forces; it is allosteric modulation (the most common type); if bound allosteric modulation (the most common type); if bound covalently, it is covalent modulation (which is more covalently, it is covalent modulation (which is more difficult to change)difficult to change)

ATP cycleATP cycle

Utilization of ATPUtilization of ATP

ATP SynthesisATP Synthesis

Two ways to produce ATPTwo ways to produce ATP Substrate PhosphorylationSubstrate Phosphorylation Oxidative PhosphorylationOxidative Phosphorylation

Substrate PhosphorylationSubstrate Phosphorylation

An ATPase binds An ATPase binds a substrate that a substrate that can be stripped can be stripped of a high energy of a high energy phosphate to phosphate to synthesize ATPsynthesize ATP

Oxidative PhosphorylationOxidative Phosphorylation

High energy electrons are High energy electrons are scavenged from the scavenged from the breakdown of food breakdown of food molecules and used to molecules and used to power an electron transport power an electron transport chain which allows the cell chain which allows the cell to synthesize ATPto synthesize ATP

Uses a series of Redox Uses a series of Redox reactions to power pumpsreactions to power pumps

Note: the PONote: the PO44-- is an ion of is an ion of

the environment and the environment and contains no extra energycontains no extra energy

Co-enzymes: NADH & Co-enzymes: NADH & FADHFADH22

The co-enzymes pick up high energy electrons and transport them to where they are needed, such as, the electron transport chain.

Oxidized Reduced

NAD+ NADHFAD+ FADH2

GlycolysisGlycolysis

Kreb CycleKreb Cycle

Electron Transport ChainElectron Transport Chain

Glycolysis: OverviewGlycolysis: Overview

2 PGAL

Transition Reaction: Acetyl-Transition Reaction: Acetyl-CoACoA

For one molecule of glu, 2 pyruvates will be processed.

Kreb Kreb CycleCycle

Kreb CycleKreb Cycle For one molecule of For one molecule of

glucose, 2 acetyl-CoAs glucose, 2 acetyl-CoAs will be processed, so will be processed, so the Kreb cycle will the Kreb cycle will make 2 complete turnsmake 2 complete turns

All of the carbon atoms All of the carbon atoms of the sugar have now of the sugar have now been converted to CObeen converted to CO22

After the co-enzymes After the co-enzymes are processed, the total are processed, the total amount of ATP amount of ATP produced per turn of produced per turn of the wheel will be 12 the wheel will be 12 ATPATP

Transition reaction

Electron Transport Electron Transport Chain (Respiratory Chain (Respiratory Chain)Chain)

NADH unloads its electrons NADH unloads its electrons at the start of the chain; at the start of the chain; yielding the maximum yielding the maximum energy release per electron energy release per electron pairpair

FADHFADH22 unloads further unloads further down the line, thereby down the line, thereby diminishing its energy diminishing its energy returnreturn

Oxygen is the final electron Oxygen is the final electron acceptor, it combines with acceptor, it combines with hydrogen to form waterhydrogen to form water

ChemiosmosiChemiosmosissGenerates a high H+ concentration in the intermembrane space

ATP synthase ATP synthase complexcomplex

H+ are pushed through H+ are pushed through the channel due to their the channel due to their electro-chemical gradientelectro-chemical gradient

This spins the rotor This spins the rotor molecules which produces molecules which produces the energy needed to the energy needed to convert ADP to ATPconvert ADP to ATP

Cellular Respiration Cellular Respiration OverviewOverview

Aerobic vs. Anaerobic Aerobic vs. Anaerobic RespirationRespiration

Anaerobic Respiration Anaerobic Respiration (fermentation)(fermentation)

Food Food ProcessingProcessing

Protein MetabolismProtein Metabolism

Proteins Proteins Amino Acids Amino Acids Amino AcidsAmino Acids

Deamination –removes NH forming a keto-acidDeamination –removes NH forming a keto-acid Transamination –transfers NH to other keto-acidTransamination –transfers NH to other keto-acid

Keto-acids can be fed into Kreb CycleKeto-acids can be fed into Kreb Cycle Amino group may form ammonia which can Amino group may form ammonia which can

be converted to urea and excreted by be converted to urea and excreted by kidneykidney

Fat MetabolismFat MetabolismTriglyceride 3 fatty acids + glycerol ( a sugar)

Fat MetabolismFat Metabolism

Fatty acids broken Fatty acids broken down 2 C’s at one down 2 C’s at one time = time = Beta-Beta-oxidationoxidation of fat of fat

8 C fatty acid would 8 C fatty acid would yield 62 ATP yield 62 ATP moleculesmolecules(17x-6) = # of ATP producedx = # of C pairs in the FA