What do you know about Cellular Respiration?

What do you know about Cellular Respiration?

Shuttling Energy Sources Across a Membrane! Different steps occur in different locations of a cell! Resources need to be moved across the mitochondrial membrane

What do you know about Cell Respiration?

Energy Flow in the Ecosystem Light energy ECOSYSTEM Photosynthesis in chloroplasts  O2 Organic molecules CO2  H2O Cellular respiration in mitochondria Figure 9.2 Energy flow and chemical recycling in ecosystems. ATP powers most cellular work ATP Heat energy

Energy is generated by Catabolic pathways involved in oxidizing organic fuels

Catabolic Pathways and ATP Production The breakdown of organic molecules is exergonic Fermentation partial sugar degradation without O2 Aerobic respiration consumes organic molecules and O2 and yields ATP

Cellular Respiration -ΔG: -686kcal/mol AKA Aerobic Respiration = REQUIRES O2 to complete! C6H12O6 + 6 O2  6 CO2 + 6 H2O + Energy (ATP + heat) -ΔG: -686kcal/mol

Redox Reactions: Oxidation and Reduction The transfer of electrons during chemical reactions releases energy stored in organic molecules This released energy is ultimately used to synthesize ATP

The Principle of Redox: Transfer of Electrons! becomes oxidized (loses electron) becomes reduced (gains electron) In oxidation, a substance loses electrons, or is oxidized (becomes more positive) In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) Figure 9.UN01 In-text figure, p. 164

More Redox! Electron donor is called the reducing agent becomes oxidized becomes reduced Electron donor is called the reducing agent  Loses Electrons Oxidized (LEO) Electron receptor is called the oxidizing agent  Gains Electrons Reduced (GER) Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds Figure 9.UN02 In-text figure, p. 164

Redox of Methane and Oxygen Gas Reactants Products becomes oxidized Energy becomes reduced Figure 9.3 Methane combustion as an energy-yielding redox reaction. Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxide Water

Oxidation of Organic Fuel Molecules During Cellular Respiration Fuel (such as glucose) is oxidized, and O2 is reduced In general lots of C-H bonds make a great fuel source becomes oxidized becomes reduced

Carbs: Why Are They Good Energy? Electrons are transferred in the form of H atoms. C-H bonds are higher in energy. The more C-H bonds the more energy! C6H12O6 CO2 Loses Electrons O2 H2O Gains Electrons H is transferred from C to O, a lower energy state  releases energy for ATP formation

Redox in Respiration Occur in Steps Enzymes control release of energy by H transfer at key steps! Not directly to O, but to coenzyme to make more energy first!

Nicotinamide Adenine Dinucleotide (NAD) and the Energy Harvesting NADH Dehydrogenase Reduction of NAD (from food) Oxidation of NADH Nicotinamide (oxidized form) Nicotinamide (reduced form) Electrons from organic compounds are usually first transferred to NAD+, a coenzyme Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP Figure 9.4 NAD as an electron shuttle.

Electron Removal From Glucose Sugar-source NADH Dehydrogenase Sugar-source NAD+ Released into the surrounding solution Figure 9.UN04 In-text figure, p. 166

Energy Production in the Electron Transport Chain H2  1/2 O2 2 H  1/2 O2 (from food via NADH) Controlled release of energy for synthesis of ATP 2 H+  2 e ATP Explosive release of heat and light energy ATP Electron transport chain Free energy, G Free energy, G ATP Figure 9.5 An introduction to electron transport chains. 2 e 1/2 O2 2 H+ H2O H2O (a) Uncontrolled reaction (b) Cellular respiration

The Stages of Cellular Respiration: A Preview Glycolysis (color-coded teal)  glucose to pyruvate 1. Pyruvate oxidation and the citric acid cycle (color-coded salmon)  completes glucose breakdown 2. Oxidative phosphorylation: electron transport and chemiosmosis (color-coded violet)  Most ATP synthesis 3.

Electrons carried via NADH Substrate-level phosphorylation Glycolysis Electrons carried via NADH Glycolysis Glucose Pyruvate MITOCHONDRION Figure 9.6 An overview of cellular respiration. CYTOSOL ATP Substrate-level phosphorylation

Electrons carried via NADH Electrons carried via NADH and FADH2 Figure 9.6-2 Electrons carried via NADH Electrons carried via NADH and FADH2 Pyruvate oxidation Glycolysis Citric acid cycle Glucose Pyruvate Acetyl CoA CYTOSOL MITOCHONDRION Figure 9.6 An overview of cellular respiration. ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation

Electrons carried via NADH Electrons carried via NADH and FADH2 Figure 9.6-3 Electrons carried via NADH Electrons carried via NADH and FADH2 Oxidative phosphorylation: electron transport and chemiosmosis Pyruvate oxidation Glycolysis Citric acid cycle Glucose Pyruvate Acetyl CoA CYTOSOL MITOCHONDRION Figure 9.6 An overview of cellular respiration. ATP ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation

BioFlix: Cellular Respiration © 2011 Pearson Education, Inc. 25

Substrate-level Phosphorylation Enzyme Enzyme ADP P Substrate ATP Product A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation

Oxidative Phosphorylation The sum of all the energy-releasing steps in the mitochondria accounts for almost 90% of the ATP generated Figure 9.7 Substrate-level phosphorylation.

Glycolysis harvests chemical energy by oxidizing glucose to pyruvate

Energy Phases of Glycolysis Energy Investment Phase Glucose 2 ADP  2 P 2 ATP used 2 phases: Energy investment Energy Payoff No Carbon released! Does not depend on oxygen! Energy Payoff Phase 4 ADP  4 P 4 ATP formed 2 NAD+  4 e  4 H+ 2 NADH  2 H+ Figure 9.8 The energy input and output of glycolysis. 2 Pyruvate  2 H2O Net Glucose 2 Pyruvate  2 H2O 4 ATP formed  2 ATP used 2 ATP 2 NAD+  4 e  4 H+ 2 NADH  2 H+

Glycolysis: Energy Investment Phase Figure 9.9-1 Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate ADP Hexokinase 1 Figure 9.9 A closer look at glycolysis.

Phosphogluco- isomerase Figure 9.9-2 Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate Fructose 6-phosphate ADP Hexokinase Phosphogluco- isomerase 1 2 Figure 9.9 A closer look at glycolysis.

Phosphogluco- isomerase Phospho- fructokinase Figure 9.9-3 Glycolysis: Energy Investment Phase ATP ATP Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate ADP ADP Hexokinase Phosphogluco- isomerase Phospho- fructokinase 1 2 3 Figure 9.9 A closer look at glycolysis.

Glycolysis: Energy Investment Phase Figure 9.9-4 Glycolysis: Energy Investment Phase ATP ATP Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate ADP ADP Hexokinase Phosphogluco- isomerase Phospho- fructokinase 1 2 3 Aldolase 4 Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate Figure 9.9 A closer look at glycolysis. To step 6 Isomerase 5

Triose phosphate dehydrogenase 1,3-Bisphospho- glycerate Figure 9.9-5 Glycolysis: Energy Payoff Phase 2 NADH 2 NAD + 2 H Triose phosphate dehydrogenase 2 P i 1,3-Bisphospho- glycerate 6 Figure 9.9 A closer look at glycolysis.

Glycolysis: Energy Payoff Phase Figure 9.9-6 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD + 2 H 2 ADP 2 Triose phosphate dehydrogenase Phospho- glycerokinase 2 P i 1,3-Bisphospho- glycerate 7 3-Phospho- glycerate 6 Figure 9.9 A closer look at glycolysis.

Glycolysis: Energy Payoff Phase Figure 9.9-7 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD + 2 H 2 ADP 2 2 Triose phosphate dehydrogenase Phospho- glycerokinase Phospho- glyceromutase 2 P i 1,3-Bisphospho- glycerate 7 3-Phospho- glycerate 8 2-Phospho- glycerate 6 Figure 9.9 A closer look at glycolysis.

Glycolysis: Energy Payoff Phase Figure 9.9-8 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 H2O 2 NAD + 2 H 2 ADP 2 2 2 Triose phosphate dehydrogenase Phospho- glycerokinase Phospho- glyceromutase Enolase 2 P i 9 1,3-Bisphospho- glycerate 7 3-Phospho- glycerate 8 2-Phospho- glycerate Phosphoenol- pyruvate (PEP) 6 Figure 9.9 A closer look at glycolysis.

Glycolysis: Energy Payoff Phase Figure 9.9-9 Glycolysis: Energy Payoff Phase 2 ATP 2 ATP 2 NADH 2 H2O 2 ADP 2 NAD + 2 H 2 ADP 2 2 2 Triose phosphate dehydrogenase Phospho- glycerokinase Phospho- glyceromutase Enolase Pyruvate kinase 2 P i 9 1,3-Bisphospho- glycerate 7 3-Phospho- glycerate 8 2-Phospho- glycerate Phosphoenol- pyruvate (PEP) 10 Pyruvate 6 Figure 9.9 A closer look at glycolysis.

Phosphogluco- isomerase Glycolysis Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate Fructose 6-phosphate ADP Figure 9.9 A closer look at glycolysis. Hexokinase Phosphogluco- isomerase Figure 9.9 A closer look at glycolysis. 1 2 Isomerizes the sugar! Adds a phosphate = energizing the glucose

Glycolysis Cuts the sugar in half! Second energy investment Glycolysis: Energy Investment Phase ATP Fructose 6-phosphate Fructose 1,6-bisphosphate ADP Cuts the sugar in half! Phospho- fructokinase Aldolase 4 3 Figure 9.9 A closer look at glycolysis. Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate Second energy investment To step 6 Isomerase 5 Switches the 3C sugar between 2 forms

Glycolysis Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD + 2 H 2 ADP 2 2 Figure 9.9 A closer look at glycolysis. Triose phosphate dehydrogenase Phospho- glycerokinase 2 P i 1,3-Bisphospho- glycerate 7 3-Phospho- glycerate 6 Removes 2 H to make an NADH and H+ Removes a phosphate to make ATP!

Phospho- glyceromutase Phosphoenol- pyruvate (PEP) Glycolysis Glycolysis: Energy Payoff Phase 2 ATP 2 H2O 2 ADP 2 2 2 2 Phospho- glyceromutase Enolase Pyruvate kinase Figure 9.9 A closer look at glycolysis. 9 3-Phospho- glycerate 8 2-Phospho- glycerate Phosphoenol- pyruvate (PEP) 10 Pyruvate Pulls off water Makes more ATP Shuffles the phosphate to a different carbon

Citric acid cycle completes the energy-yielding oxidation of organic molecules

Oxidation of Pyruvate to Acetyl CoA MITOCHONDRION CYTOSOL CO2 Coenzyme A 1 3 2 NAD NADH + H Acetyl CoA Pyruvate Transport protein This step is carried out by a multienzyme complex that catalyses three reactions to bring pyruvate into the mitochondria

Lose: 1 CO2 per pyruvate Gain: 1 NADH per pyruvate

The Citric Acid Cycle Completes the break down of pyruvate to CO2 NAD CoA NADH Completes the break down of pyruvate to CO2 The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn REMEMBER 2 pyruvate per Glucose! + H Acetyl CoA CoA CoA Citric acid cycle 2 CO2 FADH2 3 NAD FAD 3 NADH + 3 H ADP + P i ATP

Overview: Citric Acid Cycle 8 steps, each catalyzed by a specific enzyme Acetyl combines with oxaloacetatecitrate The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle

Citric acid cycle Acetyl CoA Oxaloacetate Citrate CoA-SH 1 Oxaloacetate Citrate Citric acid cycle Figure 9.12 A closer look at the citric acid cycle.

Citric acid cycle Acetyl CoA Oxaloacetate Citrate Isocitrate CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate Citric acid cycle Figure 9.12 A closer look at the citric acid cycle.

Citric acid cycle Acetyl CoA Oxaloacetate Citrate Isocitrate CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD Citric acid cycle NADH 3 + H CO2 -Ketoglutarate Figure 9.12 A closer look at the citric acid cycle.

Citric acid cycle Acetyl CoA Oxaloacetate Citrate Isocitrate CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD Citric acid cycle NADH 3 + H CO2 CoA-SH -Ketoglutarate Figure 9.12 A closer look at the citric acid cycle. 4 CO2 NAD NADH Succinyl CoA + H

Citric acid cycle Acetyl CoA Oxaloacetate Citrate Isocitrate CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD Citric acid cycle NADH 3 + H CO2 CoA-SH -Ketoglutarate Figure 9.12 A closer look at the citric acid cycle. 4 CoA-SH 5 CO2 NAD Succinate P i NADH GTP GDP Succinyl CoA + H ADP ATP

Citric acid cycle Acetyl CoA Oxaloacetate Citrate Isocitrate Fumarate CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD Citric acid cycle NADH 3 + H CO2 Fumarate CoA-SH -Ketoglutarate Figure 9.12 A closer look at the citric acid cycle. 4 6 CoA-SH 5 FADH2 CO2 NAD FAD Succinate P i NADH GTP GDP Succinyl CoA + H ADP ATP

Citric acid cycle Acetyl CoA Oxaloacetate Malate Citrate Isocitrate CoA-SH 1 H2O Oxaloacetate 2 Malate Citrate Isocitrate NAD Citric acid cycle NADH 3 7 + H H2O CO2 Fumarate CoA-SH -Ketoglutarate Figure 9.12 A closer look at the citric acid cycle. 4 6 CoA-SH 5 FADH2 CO2 NAD FAD Succinate P i NADH GTP GDP Succinyl CoA + H ADP ATP

Citric acid cycle Acetyl CoA Oxaloacetate Malate Citrate Isocitrate CoA-SH NADH + H 1 H2O NAD Oxaloacetate 8 2 Malate Citrate Isocitrate NAD Citric acid cycle NADH 3 7 + H H2O CO2 Fumarate CoA-SH -Ketoglutarate Figure 9.12 A closer look at the citric acid cycle. 4 6 CoA-SH 5 FADH2 CO2 NAD FAD Succinate P i NADH GTP GDP Succinyl CoA + H ADP ATP

Acetyl group (What’s left of the pyruvate) combines with Oxaloacetate to make Citrate Acetyl CoA Citrate is isomerized by removing water and then adding it back CoA-SH 1 H2O Figure 9.12 A closer look at the citric acid cycle. Oxaloacetate 2 Citrate Isocitrate

Isocitrate is oxidized (Loses 2 H) and reduces NAD+ A second reaction occurs, removing CO2 Isocitrate NAD NADH 3 + H CO2 CoA-SH -Ketoglutarate 4 Figure 9.12 A closer look at the citric acid cycle. More CO2 is lost, and another NAD+ is reduced. Coenzyme A makes another appearance CO2 NAD NADH Succinyl CoA + H

Succinate is oxidized by FAD to make FADH2 A phosphate group replaces CoA. The Phosphate is then transferred to GDP to make GTP Fumarate 6 CoA-SH 5 FADH2 FAD Succinate P i Figure 9.12 A closer look at the citric acid cycle. GTP GDP Succinyl CoA Succinate is oxidized by FAD to make FADH2 ADP ATP

Another redox to make NADH and oxaloacetate 8 Malate Water molecule added to rearrange bonds 7 Figure 9.12 A closer look at the citric acid cycle. H2O Fumarate

During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis

The Pathway of Electron Transport NADH 50 2 e NAD FADH2 2 e FAD Multiprotein complexes Occurs in the inner membrane (cristae) of the mitochondrion Most of the chain’s components are proteins, which exist in multiprotein complexes The carriers alternate reduced and oxidized states as they accept and donate electrons I 40 FMN II FeS FeS Q III Cyt b 30 FeS Cyt c1 IV Free energy (G) relative to O2 (kcal/mol) Cyt c Cyt a Cyt a3 20 10 2 e (originally from NADH or FADH2) 2 H + 1/2 O2 H2O

no ATP directly generated Release energy in small steps NADH and FADH2 Bring electrons to the ETC Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O2 no ATP directly generated Release energy in small steps

Oxidative Phosphorylation and the ETC Protein complex of electron carriers H H Cyt c IV Q III I ATP synth- ase II 2 H + 1/2O2 H2O FADH2 FAD Figure 9.15 Chemiosmosis couples the electron transport chain to ATP synthesis. NAD NADH ADP  P i ATP (carrying electrons from food) H 1 Electron transport chain 2 Chemiosmosis Oxidative phosphorylation Electron transfer is coupled with H+ pumping into intermembrane space of mitchondria

Chemiosmosis: Energy-Coupling Mechanism Using H+ Gradient to do Work INTERMEMBRANE SPACE H Stator Rotor The H+ gradient is referred to as a proton-motive force H+ then moves back across the membrane, passing through the proton, ATP synthase ATP synthase uses the exergonic flow of H+ to drive phosphorylation of ATP H+ generated by ETC coupled with ATP synthesis! Internal rod Figure 9.14 ATP synthase, a molecular mill. Catalytic knob ADP + P i ATP MITOCHONDRIAL MATRIX

Accounting of ATP Production by Cellular Respiration During cellular respiration, most energy flows in this sequence: glucose  NADH  electron transport chain  proton-motive force  ATP About 34% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 32-36 ATP There are several reasons why the number of ATP is not known exactly

Oxidative phosphorylation: electron transport and chemiosmosis Figure 9.16 Electron shuttles span membrane MITOCHONDRION 2 NADH or 2 FADH2 2 NADH 2 NADH 6 NADH 2 FADH2 Oxidative phosphorylation: electron transport and chemiosmosis Glycolysis Pyruvate oxidation Citric acid cycle Glucose 2 Pyruvate 2 Acetyl CoA Figure 9.16 ATP yield per molecule of glucose at each stage of cellular respiration.  2 ATP  2 ATP  about 26 or 28 ATP About 30 or 32 ATP Maximum per glucose: CYTOSOL

Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen

Anaerobic Respiration Oxygen is not used or may be poisonous! Certain fungi and bacteria undergo Glycolysis coupled to an electron transport chain but use other molecules as final electron acceptors like sulfate!

Fermentation: Anaerobic Respiration Using Substrate Level Phosphorylation Fermentation consists of glycolysis plus reactions that regenerate NAD+ Without NAD+ Glycolysis couldn’t happen

Animation: Fermentation Overview Right-click slide / select “Play” © 2011 Pearson Education, Inc. 70

Fermentation 2 ADP  2 P i 2 ATP 2 ADP  2 P i 2 ATP Glucose Glycolysis Glucose Glycolysis 2 Pyruvate 2 NAD  2 NADH 2 CO2 2 NAD  2 NADH  2 H  2 H 2 Pyruvate 2 Ethanol 2 Acetaldehyde 2 Lactate (a) Alcohol fermentation Figure 9.17 Fermentation. (b) Lactic acid fermentation In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO2 In lactic acid fermentation, pyruvate is reduced to NADH, forming lactate with no release of CO2

  2 ADP  2 P i 2 ATP Glucose Glycolysis 2 Pyruvate 2 NAD 2 NADH Figure 9.17a 2 ADP  2 P i 2 ATP Glucose Glycolysis 2 Pyruvate 2 NAD  2 NADH 2 CO2  2 H  Figure 9.17 Fermentation. 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation

2 ADP  2 P i 2 ATP Glucose Glycolysis 2 NAD  2 NADH  2 H  2 Pyruvate Figure 9.17 Fermentation. Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt, and human muscles when O2 is scarce 2 Lactate (b) Lactic acid fermentation

Importance of Pyruvate Glucose Glycolysis CYTOSOL Pyruvate Obligate anaerobes – Oxygen is poisonous! Facultative anaerobes – can go either way No O2 present: Fermentation O2 present: Aerobic cellular respiration MITOCHONDRION Ethanol, lactate, or other products Acetyl CoA Figure 9.18 Pyruvate as a key juncture in catabolism. Citric acid cycle

Glycolysis and the citric acid cycle connect to many other metabolic pathways

Catabolism of Various Food Sources Proteins Carbohydrates Fats Amino acids Sugars Glycerol Fatty acids Glycolysis accepts a wide range of carbohydrates Fatty acids are broken down by beta oxidation and yield acetyl CoA An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate Glycolysis Glucose Glyceraldehyde 3- P NH3 Pyruvate Acetyl CoA Figure 9.19 The catabolism of various molecules from food. Citric acid cycle Oxidative phosphorylation

Biosynthesis (Anabolic Pathways) The body uses small molecules to build other substances These small molecules may come directly from food, from glycolysis, or from the citric acid cycle

Feedback Mechanisms and Cell Respiration Glucose AMP Glycolysis Fructose 6-phosphate Stimulates  Phosphofructokinase   Feedback inhibition is the most common mechanism for control Fructose 1,6-bisphosphate Inhibits Inhibits If ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down Pyruvate ATP Citrate Acetyl CoA Figure 9.20 The control of cellular respiration. Citric acid cycle Oxidative phosphorylation

Fermentation vs. Anaerobic vs. Aerobic Respiration All use glycolysis (net ATP = 2) to oxidize glucose and harvest chemical energy of food In all three, NAD+ is the oxidizing agent that accepts electrons during glycolysis The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O2 in cellular respiration Cellular respiration produces 32 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule

Inputs Outputs Glycolysis Glucose 2 Pyruvate  2 ATP  2 NADH Figure 9.UN06 Inputs Outputs Glycolysis Glucose 2 Pyruvate  2 ATP  2 NADH Figure 9.UN06 Summary figure, Concept 9.2

Inputs Outputs 2 Pyruvate 2 Acetyl CoA 2 ATP 8 NADH Citric acid cycle Figure 9.UN07 Inputs Outputs 2 Pyruvate 2 Acetyl CoA 2 ATP 8 NADH Citric acid cycle 2 Oxaloacetate 6 CO2 2 FADH2 Figure 9.UN07 Summary figure, Concept 9.3

Protein complex of electron carriers Cyt c Figure 9.UN08 INTERMEMBRANE SPACE H H H Protein complex of electron carriers Cyt c IV Q III I Figure 9.UN08 Summary figure, Concept 9.4 (part 1) II 2 H + 1/2 O2 H2O FADH2 FAD NAD NADH MITOCHONDRIAL MATRIX (carrying electrons from food)

MITO- CHONDRIAL MATRIX ATP synthase Figure 9.UN09 INTER- MEMBRANE SPACE H MITO- CHONDRIAL MATRIX ATP synthase Figure 9.UN09 Summary figure, Concept 9.4 (part 2) ADP + P i H ATP

pH difference across membrane Figure 9.UN10 pH difference across membrane Figure 9.UN10 Test Your Understanding, question 8 Time

Figure 9.UN11 Figure 9.UN11 Appendix A: answer to Test Your Understanding, question 8