Cellular Re spiration Chapter 08
Dec 03, 2014
Cellular Respiration
Chapter 08
2Cellular ResCellular Respirationpiration
OutlineOutline
GlycolysisGlycolysis
Transition ReactionTransition Reaction
Citric Acid CycleCitric Acid Cycle
Electron Transport SystemElectron Transport System
FermentationFermentation
Metabolic PoolMetabolic Pool
CatabolismCatabolism
AnabolismAnabolism
3Cellular ResCellular Respirationpiration
Cellular RespirationCellular Respiration
A cellular process that requires oxygen and A cellular process that requires oxygen and gives off carbon dioxidegives off carbon dioxide
Usually involves breakdown of glucose to Usually involves breakdown of glucose to carbon dioxide and watercarbon dioxide and water
Energy extracted from glucose molecule:Energy extracted from glucose molecule:
Released step-wiseReleased step-wise
Allows ATP to be produced efficientlyAllows ATP to be produced efficiently
Oxidation-reduction enzymes include NADOxidation-reduction enzymes include NAD++ and FAD as coenzymesand FAD as coenzymes
4Glucose Breakdown:Summary Reaction
5Cellular ResCellular Respirationpiration
NADNAD++ and FAD and FAD
NADNAD++ (nicotinamide adenine dinucleotide) (nicotinamide adenine dinucleotide)Called a coenzyme of oxidation-reduction it Called a coenzyme of oxidation-reduction it can can Oxidize a metabolite by accepting electronsOxidize a metabolite by accepting electrons Reduce a metabolite by giving up electronsReduce a metabolite by giving up electrons
Each NADEach NAD++ molecule used over and over again molecule used over and over again
FAD (flavin adenine dinucleotide)FAD (flavin adenine dinucleotide)Also a coenzyme of oxidation-reductionAlso a coenzyme of oxidation-reductionSometimes used instead of NADSometimes used instead of NAD++
Accepts two electrons and two hydrogen ions Accepts two electrons and two hydrogen ions (H(H++) to become FADH) to become FADH22
6NAD+ Cycle
7Cellular ResCellular RespirationpirationCellular Respiration:Cellular Respiration:
Overview of 4 PhasesOverview of 4 PhasesGlycolysis:Glycolysis:
Occurs in cytoplasmOccurs in cytoplasm Glucose broken down to two molecules of pyruvateGlucose broken down to two molecules of pyruvate ATP is formedATP is formed
Transition reaction:Transition reaction: Both pyruvates are oxidizedBoth pyruvates are oxidized Electron energy is stored in NADHElectron energy is stored in NADH Two carbons are released as COTwo carbons are released as CO22
Citric acid cycle:Citric acid cycle: Electron energy is stored in NADH and FADHElectron energy is stored in NADH and FADH22 ATP is formedATP is formed Four carbons are released as COFour carbons are released as CO22
Electron transport chain:Electron transport chain: Extracts energy from NADH & FADHExtracts energy from NADH & FADH22 Produces 32 or 34 molecules of ATPProduces 32 or 34 molecules of ATP
8Glucose Breakdown:Overview of 4
Phases
9Cellular ResCellular RespirationpirationGlucose Breakdown:Glucose Breakdown:
GlycolysisGlycolysis
Occurs in cytoplasm outside mitochondriaOccurs in cytoplasm outside mitochondriaEnergy Investment Steps:Energy Investment Steps:
Two ATP are used to activate glucoseTwo ATP are used to activate glucoseGlucose splits into two G3P moleculesGlucose splits into two G3P molecules
Energy Harvesting Steps:Energy Harvesting Steps:Two electrons (as hydrogen atoms) are picked Two electrons (as hydrogen atoms) are picked up by two NADup by two NAD++
Four ATP produced by substrate-level Four ATP produced by substrate-level phosphorylationphosphorylation
Net gain of two ATPNet gain of two ATPBoth G3Ps converted to pyruvatesBoth G3Ps converted to pyruvates
10Glycolysis:The Balance
Sheet
11Substrate-level Phosphorylation
12Glycolysis
13Glycolysis
14Cellular ResCellular RespirationpirationGlucose Breakdown:Glucose Breakdown:
The Preparatory (Prep) ReactionThe Preparatory (Prep) Reaction
End product of glycolysis, pyruvate, enters End product of glycolysis, pyruvate, enters the mitochondrial matrixthe mitochondrial matrix
Pyruvate converted to 2-carbon acetyl groupPyruvate converted to 2-carbon acetyl group
Attached to Coenzyme A to form acetyl-CoAAttached to Coenzyme A to form acetyl-CoA
Electron picked up (as hydrogen atom) by Electron picked up (as hydrogen atom) by NADNAD++
COCO22 released, and transported out of released, and transported out of mitochondria into the cytoplasmmitochondria into the cytoplasm
15Mitochondrion:Structure &
Function
16Preparatory Reaction
17Cellular ResCellular RespirationpirationGlucose Breakdown:Glucose Breakdown:
The Citric Acid CycleThe Citric Acid Cycle
A.K.A. Krebs cycleA.K.A. Krebs cycleOccurs in matrix of mitochondriaOccurs in matrix of mitochondria
Both acetyl (CBoth acetyl (C22) groups received from the ) groups received from the preparatory reaction:preparatory reaction: Join with an enzyme CoA molecule to make acetyl-Join with an enzyme CoA molecule to make acetyl-
CoACoA Acetyl (CAcetyl (C22) group transferred to oxaloacetate (C) group transferred to oxaloacetate (C22) to ) to
make citrate (Cmake citrate (C66)) Each acetyl oxidized to two COEach acetyl oxidized to two CO22 molecules molecules Remaining 4 carbons from oxaloacetate converted Remaining 4 carbons from oxaloacetate converted
back to oxaloacetate (thus “cyclic”)back to oxaloacetate (thus “cyclic”)
NADH, FADHNADH, FADH22 capture energy rich electrons capture energy rich electronsATP formed by substrate-level phosphorylationATP formed by substrate-level phosphorylation
18The Citric Acid Cycle
19Citric Acid Cycle:Balance Sheet
20Cellular ResCellular Respirationpiration
Electron Transport ChainElectron Transport Chain
Location:Location:Eukaryotes: cristae of the mitochondriaEukaryotes: cristae of the mitochondriaAerobic Prokaryotes: plasma membraneAerobic Prokaryotes: plasma membrane
Series of carrier molecules:Series of carrier molecules:Pass energy rich electrons alongPass energy rich electrons alongComplex arrays of protein and cytochromesComplex arrays of protein and cytochromes Cytochromes are respiratory moleculesCytochromes are respiratory molecules Complex carbon rings with metal atoms in Complex carbon rings with metal atoms in centercenter
Receives electrons from NADH & FADHReceives electrons from NADH & FADH22
Produce ATP by oxidative phosphorylationProduce ATP by oxidative phosphorylation
21Cellular ResCellular Respirationpiration
Electron Transport ChainElectron Transport Chain
The fate of the hydrogens:The fate of the hydrogens:Hydrogens from NADH deliver enough energy Hydrogens from NADH deliver enough energy to make 3 ATPsto make 3 ATPs
Those from FADHThose from FADH22 have only enough for 2 have only enough for 2 ATPsATPs
““Spent” hydrogens combine with oxygenSpent” hydrogens combine with oxygenRecycling of coenzymes increases efficiencyRecycling of coenzymes increases efficiency
Once NADH delivers hydrogens, it returns (as Once NADH delivers hydrogens, it returns (as NADNAD++) to pick up more hydrogens) to pick up more hydrogens
However, hydrogens must be combined with However, hydrogens must be combined with oxygen to make wateroxygen to make water
If OIf O22 not present, NADH cannot release H not present, NADH cannot release HNo longer recycled back to NADNo longer recycled back to NAD++
22Electron Transport Chain
23Organization of Cristae
24Cellular ResCellular RespirationpirationGlucose Catabolism:Glucose Catabolism:
Overall Energy YieldOverall Energy Yield
Net yield per glucose:Net yield per glucose:
From glycolysis – 2 ATPFrom glycolysis – 2 ATP
From citric acid cycle – 2 ATPFrom citric acid cycle – 2 ATP
From electron transport chain – 32 ATPFrom electron transport chain – 32 ATP
Energy content:Energy content:
Reactant (glucose) 686 kcalReactant (glucose) 686 kcal
Energy yield (36 ATP) 263 kcalEnergy yield (36 ATP) 263 kcal
Efficiency 39%; balance is waste heatEfficiency 39%; balance is waste heat
25Overall Energy Yieldedper Glucose Molecule
26Cellular ResCellular Respirationpiration
Fermentation (1)Fermentation (1)
When oxygen limited:When oxygen limited:Spent hydrogens have no acceptorSpent hydrogens have no acceptor
NADH can’t recycle back to NADNADH can’t recycle back to NAD++
Glycolysis stops because NADGlycolysis stops because NAD++ required required
Fermentation:Fermentation:““Anaerobic” pathwayAnaerobic” pathway
Can provide rapid burst of ATPCan provide rapid burst of ATP
Provides NADProvides NAD++ for glycolysis for glycolysis
NADH combines with pyruvate to yield NADNADH combines with pyruvate to yield NAD++
27Fermentation
28Cellular ResCellular Respirationpiration
Fermentation (2)Fermentation (2)
Pyruvate reduced by NADH to:Pyruvate reduced by NADH to:LactateLactate Animals & some bacteriaAnimals & some bacteria Cheese & yogurt; sauerkrautCheese & yogurt; sauerkraut
Ethanol & carbon dioxideEthanol & carbon dioxide YeastsYeasts Bread and alcoholic beveragesBread and alcoholic beverages
Allows glycolysis to proceed faster than OAllows glycolysis to proceed faster than O22 can be can be obtainedobtainedAnaerobic exerciseAnaerobic exerciseLactic acid accumulatesLactic acid accumulatesCauses cramping and oxygen debtCauses cramping and oxygen debt
When OWhen O22 restored, lactate broken down to restored, lactate broken down to acetyl-CoA and metabolizedacetyl-CoA and metabolized
29Products of Fermentation
30Efficiency of Fermentation
InLineFigure143
31Cellular ResCellular RespirationpirationMetabolic Pool:Metabolic Pool:
Catabolism (1)Catabolism (1)
Foods:Foods:Sources of energy rich moleculesSources of energy rich molecules
Carbohydrates, fats, and proteinsCarbohydrates, fats, and proteins
Catabolism (breakdown side of metabolism)Catabolism (breakdown side of metabolism)
Breakdown products enter into respiratory Breakdown products enter into respiratory pathways as intermediatespathways as intermediatesCarbohydratesCarbohydrates
Converted into glucoseConverted into glucose
Processed as aboveProcessed as above
32The Metabolic Pool Concept
33Cellular ResCellular RespirationpirationMetabolic Pool:Metabolic Pool:
Catabolism (2)Catabolism (2)
Breakdown products enter into respiratory Breakdown products enter into respiratory pathways as intermediates (cont.)pathways as intermediates (cont.)ProteinsProteins Broken into amino acids (AAs)Broken into amino acids (AAs) Some AAs used to make other proteinsSome AAs used to make other proteins Excess AAs deaminated (NHExcess AAs deaminated (NH22 removed) in liver removed) in liver
Results in poisonous ammonia (NHResults in poisonous ammonia (NH33)) Quickly converted to ureaQuickly converted to urea
Different R-groups from AAs processed Different R-groups from AAs processed differentlydifferently Fragments enter respiratory pathways at many Fragments enter respiratory pathways at many different pointsdifferent points
34Cellular ResCellular RespirationpirationMetabolic Pool:Metabolic Pool:
Anabolism (1)Anabolism (1)
All metabolic reactions part of metabolic poolAll metabolic reactions part of metabolic pool
Intermediates from respiratory pathways can be Intermediates from respiratory pathways can be used for anabolismused for anabolism
Anabolism (build-up side of metabolism):Anabolism (build-up side of metabolism): Carbs:Carbs: Start with acetyl-CoAStart with acetyl-CoA
Basically reverses glycolysis (but different pathway)Basically reverses glycolysis (but different pathway)
FatsFats G3P converted to glycerolG3P converted to glycerol
Acetyls connected in pairs to form fatty acidsAcetyls connected in pairs to form fatty acids
Note – dietary carbohydrate RARELY converted to fat in Note – dietary carbohydrate RARELY converted to fat in humans!humans!
35Cellular ResCellular RespirationpirationMetabolic Pool:Metabolic Pool:
Anabolism (2)Anabolism (2)
Anabolism (cont.):Anabolism (cont.):Proteins:Proteins:Made up of combinations of 20 different amino Made up of combinations of 20 different amino acidsacids Some amino acids (11) can be synthesized from Some amino acids (11) can be synthesized from respiratory intermediatesrespiratory intermediates organic acids in citric acid cycle can make amino organic acids in citric acid cycle can make amino
acidsacids Add NHAdd NH2 2 – transamination– transamination
However, other amino acids (9) cannot be However, other amino acids (9) cannot be synthesized by humanssynthesized by humans Essential amino acidsEssential amino acids Must be present in diet or dieMust be present in diet or die
36Cellular ResCellular Respirationpiration
ReviewReview
GlycolysisGlycolysis
Transition ReactionTransition Reaction
Citric Acid CycleCitric Acid Cycle
Electron Transport SystemElectron Transport System
FermentationFermentation
Metabolic PoolMetabolic Pool
CatabolismCatabolism
AnabolismAnabolism
Cellular Respiration
Ending Slide Chapter 08