Cell Respiration-Introduction Energy needed to keep the entropy of the cell low Importance of ATP Autotrophs and heterotrophs-similarities and differences

What can you tell about cell respiration from the equation? Balanced Equation for Aerobic Cellular Respiration C 6 H 12 O 6 + (6)O 2  (6)CO 2 + (6)H 2 O + energy Energy (delta G=(-)140 Kcal/mol)=ATP + heat

2 ways to store energy from exergonic breakdown of glucose Reduction of NAD+ Phosphorylation of ADP

Oxidation/reduction reactions Definition of oxidation and reduction Electron and hydrogen transfer Reduced substances have a higher free energy than their oxidized counterparts

LE 9-UN161 becomes oxidized becomes reduced

LE 9-UN162a becomes reduced becomes oxidized

Coenzymes The importance of the coenzymes NAD and FAD in cellular respiration Coenzymes can alternate between the oxidized and reduced form (recycling) Coenzymes are present in the cell in limited amounts Many enzymes (dehydrogenases) in cell respiration require the oxidized coenzyme (without it, they won’t work)

LE 9-4 NAD + Nicotinamide (oxidized form) Dehydrogenase 2 e – + 2 H + 2 e – + H + NADH H+H+ H+H+ Nicotinamide (reduced form) + 2[H] (from food) +

LE 9-UN162b Dehydrogenase

ATP synthesis during Cellular Respiration Substrate level-phosphorylation Oxidative phosphorylation

Substrate-level phosphorylation Involves the transfer of a phosphate from one organic molecule to another during an enzyme catalyzed reaction Does not require membranes to occur Produces a small amount of ATP/glucose in cellular respiration (4 net ATP/glucose out of the 38 possible produced).

LE 9-7 Enzyme ADP P Substrate Product Enzyme ATP +

ATP production by Oxidative Phsophorylation Use the energy of an H+ gradient to drive the endergonic reaction of ADP + P  ATP (chemiosmosis) The phophate transferred to ADP is inorganic Membranes are required (a membrane separation two compartments)-mitochondria Occurs when reduced NAD and FAD are reoxidized (recycled) during cellular respiration Produces most of the ATP during cell respiration (34 ATP/glucose out of the maximum 38 possible)

Cellular Respiration is a multistep metabolic pathway Why is it many individual steps rather than 1 step?

LE H e – 2 H (from food via NADH) Controlled release of energy for synthesis of ATP 2 H + 2 e – H2OH2O + 1 / 2 O 2 H2H2 + H2OH2O Explosive release of heat and light energy Cellular respiration Uncontrolled reaction Free energy, G Electron transport chain

Aerobic Cellular respiration consists of three linked metabolic sequences Glycolysis Citric Acid (Kreb’s cycle) Electron Transport System

Cellular Respiration Cell Biology -Respiration-Things you should know about the metabolic sequences 1) glycolysis 2) Kreb’s cycle (including transition reaction), and 3) the electron transport system 1. Starting compound 2. end product 3. Is CO2 produced ? 4. Is NAD+ reduced? 5. Is NADH oxidized? 6. Is FAD reduced? 7. Is FADH2 oxidized? 8. Cellular location 9. Is ATP produced by substrate-level phosphorylation? If so, how much per glucose? 10. Is ATP produced by oxidative phosphorylation? If so, how much per glucose? 11. Is molecular oxygen (O2) directly involved in the sequence? 12. Is ATP used up during the sequence?

LE 9-6_3 Mitochondrion Glycolysis Pyruvate Glucose Cytosol ATP Substrate-level phosphorylation ATP Substrate-level phosphorylation Citric acid cycle ATP Oxidative phosphorylation Oxidative phosphorylation: electron transport and chemiosmosis Electrons carried via NADH Electrons carried via NADH and FADH 2

LE 9-6_1 Mitochondrion Glycolysis Pyruvate Glucose Cytosol ATP Substrate-level phosphorylation

LE 9-8 Energy investment phase Glucose 2 ATP used 2 ADP + 2 P 4 ADP + 4 P 4 ATP formed 2 NAD e – + 4 H + Energy payoff phase + 2 H + 2 NADH 2 Pyruvate + 2 H 2 O 2 ATP 2 NADH + 2 H + Glucose 4 ATP formed – 2 ATP used 2 NAD+ + 4 e – + 4 H + Net Glycolysis Citric acid cycle Oxidative phosphorylation ATP

LE 9-9a_1 Glucose ATP ADP Hexokinase ATP Glycolysis Oxidation phosphorylation Citric acid cycle Glucose-6-phosphate

LE 9-9a_2 Glucose ATP ADP Hexokinase ATP Glycolysis Oxidation phosphorylation Citric acid cycle Glucose-6-phosphate Phosphoglucoisomerase Phosphofructokinase Fructose-6-phosphate ATP ADP Fructose- 1, 6-bisphosphate Aldolase Isomerase Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate

LE 9-9b_1 2 NAD + Triose phosphate dehydrogenase + 2 H + NADH 2 1, 3-Bisphosphoglycerate 2 ADP 2 ATP Phosphoglycerokinase Phosphoglyceromutase 2-Phosphoglycerate 3-Phosphoglycerate

LE 9-9b_2 2 NAD + Triose phosphate dehydrogenase + 2 H + NADH 2 1, 3-Bisphosphoglycerate 2 ADP 2 ATP Phosphoglycerokinase Phosphoglyceromutase 2-Phosphoglycerate 3-Phosphoglycerate 2 ADP 2 ATP Pyruvate kinase 2 H 2 O Enolase Phosphoenolpyruvate Pyruvate

LE 9-18 Pyruvate Glucose CYTOSOL No O 2 present Fermentation Ethanol or lactate Acetyl CoA MITOCHONDRION O 2 present Cellular respiration Citric acid cycle

LE 9-17a CO H + 2 NADH2 NAD + 2 Acetaldehyde 2 ATP 2 ADP + 2 P i 2 Pyruvate 2 2 Ethanol Alcohol fermentation Glucose Glycolysis

LE 9-17b CO H + 2 NADH2 NAD + 2 ATP 2 ADP + 2 P i 2 Pyruvate 2 2 Lactate Lactic acid fermentation Glucose Glycolysis

Summary-Fermentation

LE 9-6_3 Mitochondrion Glycolysis Pyruvate Glucose Cytosol ATP Substrate-level phosphorylation ATP Substrate-level phosphorylation Citric acid cycle ATP Oxidative phosphorylation Oxidative phosphorylation: electron transport and chemiosmosis Electrons carried via NADH Electrons carried via NADH and FADH 2

Fermentation: 1.Recycles reduced NAD back into oxidized NAD 2.Is the same as glycolysis 3.Only occurs in yeast 4.Produces more ATP than glycolysis 5.All of the above

In which metabolic pathway(s) is CO2 produced? a) glycolysis, b) fermentation, c) citric acid cycle, d) a and b, e) b and c), f) a and c, g) all of the above, h) none of the above

In which metabolic pathway(s) ATP produced by substrate-level phosphorylation? a) glycolysis, b) fermentation, c) citric acid cycle, d) a and b, e) b and c), f) a and c, g) all of the above, h) none of the above

LE 9-11 Pyruvate (from glycolysis, 2 molecules per glucose) ATP Glycolysis Oxidation phosphorylation Citric acid cycle NAD + NADH + H + CO 2 CoA Acetyl CoA CoA Citric acid cycle CO NAD H + NADH3 ATP ADP + P i FADH 2 FAD

LE 9-10 CYTOSOL Pyruvate NAD + MITOCHONDRION Transport protein NADH + H + Coenzyme ACO 2 Acetyl Co A

LE 9-12_1 ATP Glycolysis Oxidation phosphorylation Citric acid cycle Citric acid cycle Citrate Isocitrate Oxaloacetate Acetyl CoA H2OH2O

LE 9-12_2 ATP Glycolysis Oxidation phosphorylation Citric acid cycle Citric acid cycle Citrate Isocitrate Oxaloacetate Acetyl CoA H2OH2O CO2CO2 NAD + NADH + H +  -Ketoglutarate CO2CO2 NAD + NADH + H + Succinyl CoA

LE 9-12_3 ATP Glycolysis Oxidation phosphorylation Citric acid cycle Citric acid cycle Citrate Isocitrate Oxaloacetate Acetyl CoA H2OH2O CO2CO2 NAD + NADH + H +  -Ketoglutarate CO2CO2 NAD + NADH + H + Succinyl CoA Succinate GTP GDP ADP ATP FAD FADH 2 P i Fumarate

LE 9-12_4 ATP Glycolysis Oxidation phosphorylation Citric acid cycle Citric acid cycle Citrate Isocitrate Oxaloacetate Acetyl CoA H2OH2O CO2CO2 NAD + NADH + H +  -Ketoglutarate CO2CO2 NAD + NADH + H + Succinyl CoA Succinate GTP GDP ADP ATP FAD FADH 2 P i Fumarate H2OH2O Malate NAD + NADH + H +

Summary-Citric Acid cycle

Why is the citric acid cycle important? 1.It completes the oxidation of pyruvate 2.It produces a lot of ATP by chemiomosis 3.It recycles oxidized NAD back into reduced NAD 4.It generates O2 that is needed by the ETS

If a cell is deprived of oxygen: 1.ATP production by oxidative phosphorylation will cease 2.FADH2 will not be recycled 3.The citric acid cycle will stop 4.1 and 2 5.All of the above

Which of the following is not true about the electron transport system? 1.It consists of two types of molecules, some hydrogen and some electron carriers 2.It contains cytochromes 3.It is found in the mitochondrial matrix 4.It has electron transport system components that are assymetrically distributed within the mitochondrial inner membrane 5.Some of its components are iron containing proteins

If 4 molecules of NADH are recycled by the ETS, how many ATP could be produced at the same time?

The mitochondrial inner membrane: 1.Is normally impermeable to H+ 2.Separates the inner membrane space and the matrix in the mitochondria 3.Contains a channel protein which is also an ATPase enzyme 4.Is the location of the electron transport system 5.All of the above

LE 9-13 ATP Glycolysis Oxidative phosphorylation: electron transport and chemiosmosis Citric acid cycle NADH 50 FADH 2 40 FMN FeS I FAD FeS II III Q FeS Cyt b Cyt c Cyt c 1 Cyt a Cyt a 3 IV 10 0 Multiprotein complexes Free energy (G) relative to O2 (kcal/mol) H2OH2O O2O2 2 H / 2

LE 9-15 Protein complex of electron carriers H+H+ ATP Glycolysis Oxidative phosphorylation: electron transport and chemiosmosis Citric acid cycle H+H+ Q III I II FAD FADH 2 + H + NADH NAD + (carrying electrons from food) Inner mitochondrial membrane Inner mitochondrial membrane Mitochondrial matrix Intermembrane space H+H+ H+H+ Cyt c IV 2H / 2 O 2 H2OH2O ADP + H+H+ ATP synthase Electron transport chain Electron transport and pumping of protons (H + ), Which create an H + gradient across the membrane P i Chemiosmosis ATP synthesis powered by the flow of H + back across the membrane Oxidative phosphorylation

LE 9-14 INTERMEMBRANE SPACE H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP MITOCHONDRAL MATRIX ADP + P i A rotor within the membrane spins as shown when H + flows past it down the H + gradient. A stator anchored in the membrane holds the knob stationary. A rod (or “stalk”) extending into the knob also spins, activating catalytic sites in the knob. Three catalytic sites in the stationary knob join inorganic phosphate to ADP to make ATP.

Summary-Electron Transport Sytem

LE 9-16 CYTOSOL Electron shuttles span membrane 2 NADH or 2 FADH 2 MITOCHONDRION Oxidative phosphorylation: electron transport and chemiosmosis 2 FADH 2 2 NADH6 NADH Citric acid cycle 2 Acetyl CoA 2 NADH Glycolysis Glucose 2 Pyruvate + 2 ATP by substrate-level phosphorylation + 2 ATP by substrate-level phosphorylation + about 32 or 34 ATP by oxidation phosphorylation, depending on which shuttle transports electrons form NADH in cytosol About 36 or 38 ATP Maximum per glucose:

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cytoplasm Mito c hondrion Electron transport chain 2 net 2 glucose subtotal 2 CO 2 4 CO 2 FADH or O 2 ATP or 34 ATP 2 pyruvate 2 acetyl CoA Citric acid cycle NADH + H + glycolysis 6 H 2 O 36 or 38 total

Summary-Energy Yield-Aerobic Cellular Respiration

LE 9-19 Citric acid cycle Oxidative phosphorylation Proteins NH 3 Amino acids Sugars Carbohydrates Glycolysis Glucose Glyceraldehyde-3- P Pyruvate Acetyl CoA Fatty acids Glycerol Fats

LE 9-20 Citric acid cycle Oxidative phosphorylation Glycolysis Glucose Pyruvate Acetyl CoA Fructose-6-phosphate Phosphofructokinase Fructose-1,6-bisphosphate – Inhibits ATP Citrate Inhibits Stimulates AMP + –

Overall Summary-Cell Respiration