Cell RespirationCell Respiration

CC66HH1212OO66 + 6 O + 6 O22 + 6 H + 6 H22O O 6 CO 6 CO22 + 12 H + 12 H22O + ATPO + ATP

Overview: 4 main Overview: 4 main processesprocesses

GlycolysisGlycolysis

Pyruvate oxidationPyruvate oxidation

Citric Acid CycleCitric Acid Cycle

Electron Transport ChainElectron Transport Chain

GlycolysisGlycolysis

““Sugar splitting” – 1 molecule of Sugar splitting” – 1 molecule of glucose (6-C) is split into 2 glucose (6-C) is split into 2 pyruvates (3-C)pyruvates (3-C)

Occurs in cytosolOccurs in cytosol ATP, NADATP, NAD++, and P, and Pii float freely float freely

Series of reactions catalyzed by Series of reactions catalyzed by specific enzymesspecific enzymes

11stst phase of Glycolysis is phase of Glycolysis is EndergonicEndergonic

Requires input of ATPRequires input of ATP

Glucose is stable, not readily Glucose is stable, not readily broken downbroken down

2 phosphorylation rxns. transfer P 2 phosphorylation rxns. transfer P from ATP to sugar from ATP to sugar fructose 1,6- fructose 1,6-biphosphatebiphosphate

Fructose 1,6-biphosphate broken Fructose 1,6-biphosphate broken down into 2 3-C molecules: down into 2 3-C molecules: dihydroxyacetone phosphate and dihydroxyacetone phosphate and glyceraldehyde-3-phosphate (G3P)glyceraldehyde-3-phosphate (G3P)

Dihydroxyacetone phosphate Dihydroxyacetone phosphate converted to G3Pconverted to G3P

OVERALL: Glucose + 2ATP OVERALL: Glucose + 2ATP 2 2 G3P + 2 ADPG3P + 2 ADP

22ndnd phase of Glycolysis is phase of Glycolysis is ExergonicExergonic

G3P is oxidized to produce NADH + G3P is oxidized to produce NADH + HH++

Since 2 G3P, 2 NADH are produced Since 2 G3P, 2 NADH are produced (used later to produce ATP)(used later to produce ATP)

Substrate-level phosphorylationSubstrate-level phosphorylation- - PP is transferredis transferred from intermediate to from intermediate to ADPADP 2x per G3P2x per G3P Total of 4 ATP madeTotal of 4 ATP made

Glycolysis Summary:Glycolysis Summary:

http://programs.northlandcollege.edu/biology/Biology1111/animations/glycolysis.html

OVERALL REACTION:OVERALL REACTION: http://www.science.smith.edu/department

s/Biology/Bio231/glycolysis.html

Glucose + 2 ATP Glucose + 2 ATP 2 pyruvate + 2NADH + 2 pyruvate + 2NADH + 4 ATP4 ATP

(net gain of 2 ATP)(net gain of 2 ATP)

Remaining Processes occur in Remaining Processes occur in the Mitochondriathe Mitochondria

Pyruvate OxidationPyruvate Oxidation

Pyruvate enter mitochondria in Pyruvate enter mitochondria in eukaryoteseukaryotes

Pyruvate Dehydrogenase catalyses Pyruvate Dehydrogenase catalyses oxidative decarboxylationoxidative decarboxylation Carboxyl removed as COCarboxyl removed as CO22

2-C fragment becomes oxidized 2-C fragment becomes oxidized creating NADHcreating NADH

2-C acetyl group attached to coenzyme 2-C acetyl group attached to coenzyme AA

Overall:Overall:

2 puruvate + 2 NAD2 puruvate + 2 NAD++ + 2 CoA + 2 CoA

2 acetyl CoA + 2 NADH + 2 CO2 acetyl CoA + 2 NADH + 2 CO22

Citric Acid CycleCitric Acid Cycle 11stst reaction: acetyl CoA transfers 2-C reaction: acetyl CoA transfers 2-C

acetyl group to 4-C oxaloacetate to get acetyl group to 4-C oxaloacetate to get citratecitrate

Series of reactions:Series of reactions: 2 CO2 CO22 are removed yielding 4-C compound are removed yielding 4-C compound Oxidation occurs yielding 3 NADH and 1 Oxidation occurs yielding 3 NADH and 1

FADHFADH22 per acetyl coA per acetyl coA 1 ATP produced by substrate level 1 ATP produced by substrate level

phosphorylationphosphorylation Oxaloacetate is regeneratedOxaloacetate is regenerated

Citric Acid CycleCitric Acid Cycle

Electron Transport ChainElectron Transport Chain ETC is series of electron ETC is series of electron

carriers embedded in carriers embedded in inner mitochondrial inner mitochondrial membrane of membrane of eukaryotes (plasma eukaryotes (plasma membrane of membrane of prokaryotes)prokaryotes)

Electrons produced Electrons produced during glycolysis, during glycolysis, pyruvate oxidation, and pyruvate oxidation, and Citric Acid Cycle enter Citric Acid Cycle enter ETC via carrier ETC via carrier molecules molecules

Overview of ETC:Overview of ETC:

High energy electrons are passed High energy electrons are passed along ETC in series of exergonic along ETC in series of exergonic reactionsreactions

Energy from these rxns. drives ATP Energy from these rxns. drives ATP synthesis (endergonic)synthesis (endergonic)

This is This is oxidative phosphorylationoxidative phosphorylation – – result of redox rxns.result of redox rxns.

3 of the 4 complexes are proton 3 of the 4 complexes are proton pumps – pump Hpumps – pump H++ into the into the intermembrane spaceintermembrane space

Complex I – accepts e- from NADH Complex I – accepts e- from NADH and transfers it via ubiquinone and transfers it via ubiquinone (aka coenzyme Q) to Complex III(aka coenzyme Q) to Complex III

Complex II – accepts e- from FADHComplex II – accepts e- from FADH22 and transfers via ubiquinoneand transfers via ubiquinone

Complex III – accepts e- from Complex III – accepts e- from ubiquinone and transfers them via ubiquinone and transfers them via cytochrome c to Complex IVcytochrome c to Complex IV

Final Electron acceptor is Oxygen (1/2 Final Electron acceptor is Oxygen (1/2 OO22) – it accepts 2 e- and combines ) – it accepts 2 e- and combines with 2 protons to create waterwith 2 protons to create water

Aerobic respiration – requires OAerobic respiration – requires O22; ; without it as final e- acceptor, entire without it as final e- acceptor, entire chain backs upchain backs up

http://www.science.smith.edu/departments/Biology/Bio231/etc.html

http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter9/animations.html#

http://www.stolaf.edu/people/http://www.stolaf.edu/people/giannini/flashanimat/metabolism/giannini/flashanimat/metabolism/mido%20e%20transport.swfmido%20e%20transport.swf

ChemiosmosisChemiosmosis

ETC is coupled to ATP synthesis by ETC is coupled to ATP synthesis by proton gradientproton gradient

Concentration of HConcentration of H++ in intermembrane in intermembrane space is much higher than matrix space is much higher than matrix

HH++ diffuses down its gradient through diffuses down its gradient through ATP synthase - exergonicATP synthase - exergonic

Exergonic diffusion coupled to endergonic Exergonic diffusion coupled to endergonic ATP synthesisATP synthesis

http://vcell.ndsu.nodak.edu/animations/http://vcell.ndsu.nodak.edu/animations/atpgradient/movie.htm atpgradient/movie.htm

http://www.stolaf.edu/people/giannini/http://www.stolaf.edu/people/giannini/flashanimat/metabolism/atpsyn1.swf flashanimat/metabolism/atpsyn1.swf

http://www.stolaf.edu/people/giannini/http://www.stolaf.edu/people/giannini/flashanimat/metabolism/atpsyn2.swfflashanimat/metabolism/atpsyn2.swf

SO WHAT’S THE POINT??SO WHAT’S THE POINT??

Glycolysis gives us 2 ATP (net) + 2 Glycolysis gives us 2 ATP (net) + 2 NADHNADH

Pyruvate oxidation– 2 NADH + 2 COPyruvate oxidation– 2 NADH + 2 CO22

Citric Acid Cycle – 2 ATP + 4 COCitric Acid Cycle – 2 ATP + 4 CO2 2 + 6 + 6 NADH + 2FADHNADH + 2FADH22

ADDING UP ATPADDING UP ATP

Each NADH yields 3 ATP, so Each NADH yields 3 ATP, so Glycolysis – 2 NADH Glycolysis – 2 NADH 6 ATP 6 ATP

**except for most eukaryotic cells which **except for most eukaryotic cells which shuttle e- of NADH across mit. Mem., costing shuttle e- of NADH across mit. Mem., costing 1 ATP/NADH 1 ATP/NADH

Pyruvate oxidation – 2 NADH Pyruvate oxidation – 2 NADH 6 ATP 6 ATP Citric Acid Cycle – 6 NADH Citric Acid Cycle – 6 NADH 18 ATP 18 ATP

Each FADHEach FADH22 yields 2 ATP yields 2 ATP Citric Acid Cycle – 2 FADHCitric Acid Cycle – 2 FADH22 4 ATP 4 ATP

GRAND TOTALS…GRAND TOTALS…

Glycolysis = 2 ATPGlycolysis = 2 ATP

Citric Acid Cycle = 2 ATPCitric Acid Cycle = 2 ATP

ETC = 32 – 34 ATPETC = 32 – 34 ATP

Aerobic Respiration = 36 – 38 ATPAerobic Respiration = 36 – 38 ATP

Efficiency (i.e., Efficiency (i.e., thermodynamics)thermodynamics)

Burning glucose releases 686 kcal/mol heatBurning glucose releases 686 kcal/mol heat

Free energy in phosphate bonds of ATP = Free energy in phosphate bonds of ATP = 7.6 kcal7.6 kcal

7.6 kcal/mol ATP x 36 ATP = 274 kcal/mol7.6 kcal/mol ATP x 36 ATP = 274 kcal/mol

Efficiency of aerobic resp. = 274/686 = 40%Efficiency of aerobic resp. = 274/686 = 40% Rest is lost as heatRest is lost as heat