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cellular respiration and fermentation

This document provides an overview and summaries of key concepts from Chapter 9 of Campbell Biology, Ninth Edition, which discusses cellular respiration and fermentation. The chapter examines how cells harvest energy from organic molecules like glucose through three main stages: glycolysis, the citric acid cycle, and oxidative phosphorylation. Glycolysis breaks down glucose into pyruvate, generating a small amount of ATP. The citric acid cycle then completes the oxidation of pyruvate. Finally, oxidative phosphorylation involves an electron transport chain that generates the majority of ATP.

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LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 9 Cellular Respiration and Fermentation Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc.
Overview: Life Is Work • Living cells require energy from outside sources • Some animals, such as the chimpanzee, obtain energy by eating plants, and some animals feed on other organisms that eat plants © 2011 Pearson Education, Inc.
Figure 9.1
• Energy flows into an ecosystem as sunlight and leaves as heat • Photosynthesis generates O2 and organic molecules, which are used in cellular respiration • Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work © 2011 Pearson Education, Inc.
Figure 9.2 Light energy ECOSYSTEM Photosynthesis in chloroplasts CO2 + H2O Organic + O2 molecules Cellular respiration in mitochondria ATP powers ATP most cellular work Heat energy
Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels • Several processes are central to cellular respiration and related pathways © 2011 Pearson Education, Inc.
Catabolic Pathways and Production of ATP • The breakdown of organic molecules is exergonic • Fermentation is a partial degradation of sugars that occurs without O2 • Aerobic respiration consumes organic molecules and O2 and yields ATP • Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2 © 2011 Pearson Education, Inc.
• Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration • Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat) © 2011 Pearson Education, Inc.
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 © 2011 Pearson Education, Inc.
The Principle of Redox • Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions • In oxidation, a substance loses electrons, or is oxidized • In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) © 2011 Pearson Education, Inc.
Figure 9.UN01 becomes oxidized (loses electron) becomes reduced (gains electron)
Figure 9.UN02 becomes oxidized becomes reduced
• The electron donor is called the reducing agent • The electron receptor is called the oxidizing agent • Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds • An example is the reaction between methane and O2 © 2011 Pearson Education, Inc.
Figure 9.3 Reactants Products becomes oxidized Energy becomes reduced Methane Oxygen Carbon dioxide Water (reducing (oxidizing agent) agent)
Oxidation of Organic Fuel Molecules During Cellular Respiration • During cellular respiration, the fuel (such as glucose) is oxidized, and O2 is reduced © 2011 Pearson Education, Inc.
Figure 9.UN03 becomes oxidized becomes reduced
Stepwise Energy Harvest via NAD+ and the Electron Transport Chain • In cellular respiration, glucose and other organic molecules are broken down in a series of steps • Electrons from organic compounds are usually first transferred to NAD+, a coenzyme • As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration • Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP © 2011 Pearson Education, Inc.
Figure 9.4 NAD+ NADH Dehydrogenase Reduction of NAD+ (from food) Oxidation of NADH Nicotinamide Nicotinamide (oxidized form) (reduced form)
Figure 9.UN04 Dehydrogenase
• NADH passes the electrons to the electron transport chain • Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction • O2 pulls electrons down the chain in an energy- yielding tumble • The energy yielded is used to regenerate ATP © 2011 Pearson Education, Inc.
Figure 9.5 H2 + 1/2 O2 2H + /2 O2 1 (from food via NADH) Controlled release of 2H + 2e + − energy for synthesis of ATP Elec chain ATP Free energy, G Free energy, G tron Explosive ATP release of tran heat and light ATP energy spor 2 e− t 1 /2 O2 2H + H2O H2O (a) Uncontrolled reaction (b) Cellular respiration
The Stages of Cellular Respiration: A Preview • Harvesting of energy from glucose has three stages – Glycolysis (breaks down glucose into two molecules of pyruvate) – The citric acid cycle (completes the breakdown of glucose) – Oxidative phosphorylation (accounts for most of the ATP synthesis) © 2011 Pearson Education, Inc.
Figure 9.UN05 1. Glycolysis (color-coded teal throughout the chapter) 2. Pyruvate oxidation and the citric acid cycle (color-coded salmon) 3. Oxidative phosphorylation: electron transport and chemiosmosis (color-coded violet)
Figure 9.6-1 Electrons carried via NADH Glycolysis Glucose Pyruvate CYTOSOL MITOCHONDRION ATP Substrate-level phosphorylation
Figure 9.6-2 Electrons Electrons carried carried via NADH and via NADH FADH2 Pyruvate Glycolysis Citric oxidation acid Glucose Pyruvate Acetyl CoA cycle CYTOSOL MITOCHONDRION ATP ATP Substrate-level Substrate-level phosphorylation phosphorylation
Figure 9.6-3 Electrons Electrons carried carried via NADH and via NADH FADH2 Oxidative Pyruvate Glycolysis Citric phosphorylation: oxidation acid electron transport Glucose Pyruvate Acetyl CoA cycle and chemiosmosis CYTOSOL MITOCHONDRION ATP ATP ATP Substrate-level Substrate-level Oxidative phosphorylation phosphorylation phosphorylation
• The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions © 2011 Pearson Education, Inc.
• Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration • A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation • For each molecule of glucose degraded to CO2 and water by respiration, the cell makes up to 32 molecules of ATP © 2011 Pearson Education, Inc.
Figure 9.7 Enzyme Enzyme ADP P Substrate ATP Product
Concept 9.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate • Glycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvate • Glycolysis occurs in the cytoplasm and has two major phases – Energy investment phase – Energy payoff phase • Glycolysis occurs whether or not O2 is present © 2011 Pearson Education, Inc.
Figure 9.8 Energy Investment Phase Glucose 2 ADP + 2 P 2 ATP used Energy Payoff Phase 4 ADP + 4 P 4 ATP formed 2 NAD+ + 4 e− + 4 H+ 2 NADH + 2 H+ 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+
Figure 9.9-1 Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate ADP Hexokinase 1
Figure 9.9-2 Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate Fructose 6-phosphate ADP Hexokinase Phosphogluco- isomerase 1 2
Figure 9.9-3 Glycolysis: Energy Investment Phase ATP ATP Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate ADP ADP Hexokinase Phosphogluco- Phospho- isomerase fructokinase 1 2 3
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- Phospho- isomerase fructokinase 1 2 3 Aldolase 4 Dihydroxyacetone Glyceraldehyde phosphate 3-phosphate To Isomerase 5 step 6
Figure 9.9-5 Glycolysis: Energy Payoff Phase 2 NADH 2 NAD+ + 2 H+ Triose phosphate 2Pi dehydrogenase 1,3-Bisphospho- 6 glycerate
Figure 9.9-6 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD+ + 2 H+ 2 ADP 2 Triose Phospho- phosphate 2Pi glycerokinase dehydrogenase 1,3-Bisphospho- 7 3-Phospho- 6 glycerate glycerate
Figure 9.9-7 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD+ + 2 H+ 2 ADP 2 2 Triose Phospho- Phospho- phosphate glyceromutase 2Pi glycerokinase dehydrogenase 1,3-Bisphospho- 7 3-Phospho- 8 2-Phospho- 6 glycerate glycerate glycerate
Figure 9.9-8 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 H2O 2 NAD+ + 2 H+ 2 ADP 2 2 2 Triose Phospho- Phospho- Enolase phosphate glyceromutase 2Pi glycerokinase dehydrogenase 9 1,3-Bisphospho- 7 3-Phospho- 8 2-Phospho- Phosphoenol- 6 glycerate glycerate glycerate pyruvate (PEP)
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 Phospho- Phospho- Enolase Pyruvate phosphate glyceromutase kinase 2Pi glycerokinase dehydrogenase 9 1,3-Bisphospho- 7 3-Phospho- 8 2-Phospho- Phosphoenol- 10 Pyruvate 6 glycerate glycerate glycerate pyruvate (PEP)
Figure 9.9a Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate Fructose 6-phosphate ADP Hexokinase Phosphogluco- isomerase 1 2
Figure 9.9b Glycolysis: Energy Investment Phase ATP Fructose 6-phosphate Fructose 1,6-bisphosphate ADP Phospho- fructokinase Aldolase 4 3 Dihydroxyacetone Glyceraldehyde phosphate 3-phosphate To Isomerase 5 step 6
Figure 9.9c Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD+ + 2 H+ 2 ADP 2 2 Triose Phospho- phosphate 2Pi glycerokinase dehydrogenase 1,3-Bisphospho- 7 3-Phospho- 6 glycerate glycerate
Figure 9.9d Glycolysis: Energy Payoff Phase 2 ATP 2 H2O 2 ADP 2 2 2 2 Phospho- Enolase Pyruvate glyceromutase kinase 9 3-Phospho- 8 2-Phospho- Phosphoenol- 10 Pyruvate glycerate glycerate pyruvate (PEP)
Concept 9.3: After pyruvate is oxidized, the citric acid cycle completes the energy- yielding oxidation of organic molecules • In the presence of O2, pyruvate enters the mitochondrion (in eukaryotic cells) where the oxidation of glucose is completed © 2011 Pearson Education, Inc.
Oxidation of Pyruvate to Acetyl CoA • Before the citric acid cycle can begin, pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle • This step is carried out by a multienzyme complex that catalyses three reactions © 2011 Pearson Education, Inc.
Figure 9.10 MITOCHONDRION CYTOSOL CO2 Coenzyme A 1 3 2 NAD+ NADH + H+ Acetyl CoA Pyruvate Transport protein
The Citric Acid Cycle • The citric acid cycle, also called the Krebs cycle, completes the break down of pyrvate to CO2 • The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn © 2011 Pearson Education, Inc.
Figure 9.11 Pyruvate CO2 NAD + CoA NADH + H+ Acetyl CoA CoA CoA Citric acid cycle 2 CO2 FADH2 3 NAD+ FAD 3 NADH + 3 H+ ADP + P i ATP
• The citric acid cycle has eight steps, each catalyzed by a specific enzyme • The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate • The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle • The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain © 2011 Pearson Education, Inc.
Figure 9.12-1 Acetyl CoA CoA-SH 1 Oxaloacetate Citrate Citric acid cycle
Figure 9.12-2 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate Citric acid cycle
Figure 9.12-3 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric 3 NADH acid + H+ cycle CO2 α-Ketoglutarate
Figure 9.12-4 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric 3 NADH acid + H+ cycle CO2 CoA-SH α-Ketoglutarate 4 CO2 NAD+ NADH Succinyl + H+ CoA
Figure 9.12-5 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric 3 NADH acid + H+ cycle CO2 CoA-SH α-Ketoglutarate 4 CoA-SH 5 CO2 NAD+ Succinate Pi NADH GTP GDP Succinyl + H+ CoA ADP ATP
Figure 9.12-6 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric 3 NADH acid + H+ cycle CO2 Fumarate CoA-SH α-Ketoglutarate 6 4 CoA-SH FADH2 5 CO2 NAD+ FAD Succinate Pi NADH GTP GDP Succinyl + H+ CoA ADP ATP
Figure 9.12-7 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric 3 NADH 7 acid + H+ H2 O cycle CO2 Fumarate CoA-SH α-Ketoglutarate 6 4 CoA-SH FADH2 5 CO2 NAD+ FAD Succinate Pi NADH GTP GDP Succinyl + H+ CoA ADP ATP
Figure 9.12-8 Acetyl CoA CoA-SH NADH + H+ 1 H2O NAD+ 8 Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric 3 NADH 7 acid + H+ H2 O cycle CO2 Fumarate CoA-SH α-Ketoglutarate 6 4 CoA-SH FADH2 5 CO2 NAD+ FAD Succinate Pi NADH GTP GDP Succinyl + H+ CoA ADP ATP
Figure 9.12a Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate
Figure 9.12b Isocitrate NAD+ NADH 3 + H+ CO2 CoA-SH α-Ketoglutarate 4 CO2 NAD+ NADH Succinyl + H+ CoA
Figure 9.12c Fumarate 6 CoA-SH FADH2 5 FAD Succinate Pi GTP GDP Succinyl CoA ADP ATP
Figure 9.12d NADH + H+ NAD+ 8 Oxaloacetate Malate 7 H2O Fumarate
Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis • Following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the energy extracted from food • These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation © 2011 Pearson Education, Inc.
The Pathway of Electron Transport • The electron transport chain is 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 • Electrons drop in free energy as they go down the chain and are finally passed to O2, forming H2O © 2011 Pearson Education, Inc.
Figure 9.13 NADH 50 2 e− NAD+ FADH2 2 e− FAD Multiprotein Free energy (G) relative to O2 (kcal/mol) 40 FMN I complexes Fe• S II Fe• S Q III Cyt b Fe• S 30 Cyt c1 IV Cyt c Cyt a Cyt a3 20 2 e− 10 (originally from NADH or FADH2) 0 2 H+ + 1/2 O2 H2O
• Electrons are transferred from NADH or FADH2 to the electron transport chain • Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O2 • The electron transport chain generates no ATP directly • It breaks the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts © 2011 Pearson Education, Inc.
Chemiosmosis: The Energy-Coupling Mechanism • Electron transfer in the electron transport chain causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space • 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 • This is an example of chemiosmosis, the use of energy in a H+ gradient to drive cellular work © 2011 Pearson Education, Inc.
Figure 9.14 INTERMEMBRANE SPACE H+ Stator Rotor Internal rod Catalytic knob ADP + Pi ATP MITOCHONDRIAL MATRIX
Figure 9.15 H+ H + Protein H + complex H+ Cyt c of electron carriers IV Q III I ATP II synth- 2 H+ + 1/2O2 H2O ase FADH2 FAD NADH NAD+ ADP + P i ATP (carrying electrons from food) H+ 1 Electron transport chain 2 Chemiosmosis Oxidative phosphorylation
• The energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis • The H+ gradient is referred to as a proton- motive force, emphasizing its capacity to do work © 2011 Pearson Education, Inc.
An 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 ATP • There are several reasons why the number of ATP is not known exactly © 2011 Pearson Education, Inc.
Figure 9.16 Electron shuttles MITOCHONDRION span membrane 2 NADH or 2 FADH2 2 NADH 2 NADH 6 NADH 2 FADH2 Glycolysis Pyruvate oxidation Oxidative Citric phosphorylation: Glucose 2 Pyruvate 2 Acetyl CoA acid electron transport cycle and chemiosmosis + 2 ATP + 2 ATP + about 26 or 28 ATP About Maximum per glucose: 30 or 32 ATP CYTOSOL
Concept 9.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen • Most cellular respiration requires O2 to produce ATP • Without O2, the electron transport chain will cease to operate • In that case, glycolysis couples with fermentation or anaerobic respiration to produce ATP © 2011 Pearson Education, Inc.
• Anaerobic respiration uses an electron transport chain with a final electron acceptor other than O2, for example sulfate • Fermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP © 2011 Pearson Education, Inc.
Types of Fermentation • Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis • Two common types are alcohol fermentation and lactic acid fermentation © 2011 Pearson Education, Inc.
• In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO2 • Alcohol fermentation by yeast is used in brewing, winemaking, and baking © 2011 Pearson Education, Inc.
Figure 9.17 2 ADP + 2 P 2 ATP 2 ADP + 2 P 2 ATP i i 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 (b) Lactic acid fermentation
Figure 9.17a 2 ADP + 2 P i 2 ATP Glucose Glycolysis 2 Pyruvate 2 NAD + 2 NADH 2 CO2 + 2 H+ 2 Ethanol 2 Acetaldehyde (a) Alcohol fermentation
• In lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2 • Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt • Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce © 2011 Pearson Education, Inc.
Figure 9.17b 2 ADP + 2 P i 2 ATP Glucose Glycolysis 2 NAD + 2 NADH + 2 H+ 2 Pyruvate 2 Lactate (b) Lactic acid fermentation
Comparing Fermentation with Anaerobic and 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 © 2011 Pearson Education, Inc.
• Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O2 • Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration • In a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes © 2011 Pearson Education, Inc.

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cellular respiration and fermentation

  • 1.
    LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 9 Cellular Respiration and Fermentation Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc.
  • 2.
    Overview: Life IsWork • Living cells require energy from outside sources • Some animals, such as the chimpanzee, obtain energy by eating plants, and some animals feed on other organisms that eat plants © 2011 Pearson Education, Inc.
  • 3.
  • 4.
    • Energy flowsinto an ecosystem as sunlight and leaves as heat • Photosynthesis generates O2 and organic molecules, which are used in cellular respiration • Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work © 2011 Pearson Education, Inc.
  • 5.
    Figure 9.2 Light energy ECOSYSTEM Photosynthesis in chloroplasts CO2 + H2O Organic + O2 molecules Cellular respiration in mitochondria ATP powers ATP most cellular work Heat energy
  • 6.
    Concept 9.1: Catabolicpathways yield energy by oxidizing organic fuels • Several processes are central to cellular respiration and related pathways © 2011 Pearson Education, Inc.
  • 7.
    Catabolic Pathways andProduction of ATP • The breakdown of organic molecules is exergonic • Fermentation is a partial degradation of sugars that occurs without O2 • Aerobic respiration consumes organic molecules and O2 and yields ATP • Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2 © 2011 Pearson Education, Inc.
  • 8.
    • Cellular respirationincludes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration • Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat) © 2011 Pearson Education, Inc.
  • 9.
    Redox Reactions: Oxidationand Reduction • The transfer of electrons during chemical reactions releases energy stored in organic molecules • This released energy is ultimately used to synthesize ATP © 2011 Pearson Education, Inc.
  • 10.
    The Principle ofRedox • Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions • In oxidation, a substance loses electrons, or is oxidized • In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) © 2011 Pearson Education, Inc.
  • 11.
    Figure 9.UN01 becomes oxidized (loses electron) becomes reduced (gains electron)
  • 12.
    Figure 9.UN02 becomes oxidized becomes reduced
  • 13.
    • The electrondonor is called the reducing agent • The electron receptor is called the oxidizing agent • Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds • An example is the reaction between methane and O2 © 2011 Pearson Education, Inc.
  • 14.
    Figure 9.3 Reactants Products becomes oxidized Energy becomes reduced Methane Oxygen Carbon dioxide Water (reducing (oxidizing agent) agent)
  • 15.
    Oxidation of OrganicFuel Molecules During Cellular Respiration • During cellular respiration, the fuel (such as glucose) is oxidized, and O2 is reduced © 2011 Pearson Education, Inc.
  • 16.
    Figure 9.UN03 becomes oxidized becomes reduced
  • 17.
    Stepwise Energy Harvestvia NAD+ and the Electron Transport Chain • In cellular respiration, glucose and other organic molecules are broken down in a series of steps • Electrons from organic compounds are usually first transferred to NAD+, a coenzyme • As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration • Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP © 2011 Pearson Education, Inc.
  • 18.
    Figure 9.4 NAD+ NADH Dehydrogenase Reduction of NAD+ (from food) Oxidation of NADH Nicotinamide Nicotinamide (oxidized form) (reduced form)
  • 19.
    Figure 9.UN04 Dehydrogenase
  • 20.
    • NADH passesthe electrons to the electron transport chain • Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction • O2 pulls electrons down the chain in an energy- yielding tumble • The energy yielded is used to regenerate ATP © 2011 Pearson Education, Inc.
  • 21.
    Figure 9.5 H2 + 1/2 O2 2H + /2 O2 1 (from food via NADH) Controlled release of 2H + 2e + − energy for synthesis of ATP Elec chain ATP Free energy, G Free energy, G tron Explosive ATP release of tran heat and light ATP energy spor 2 e− t 1 /2 O2 2H + H2O H2O (a) Uncontrolled reaction (b) Cellular respiration
  • 22.
    The Stages ofCellular Respiration: A Preview • Harvesting of energy from glucose has three stages – Glycolysis (breaks down glucose into two molecules of pyruvate) – The citric acid cycle (completes the breakdown of glucose) – Oxidative phosphorylation (accounts for most of the ATP synthesis) © 2011 Pearson Education, Inc.
  • 23.
    Figure 9.UN05 1.Glycolysis (color-coded teal throughout the chapter) 2. Pyruvate oxidation and the citric acid cycle (color-coded salmon) 3. Oxidative phosphorylation: electron transport and chemiosmosis (color-coded violet)
  • 24.
    Figure 9.6-1 Electrons carried via NADH Glycolysis Glucose Pyruvate CYTOSOL MITOCHONDRION ATP Substrate-level phosphorylation
  • 25.
    Figure 9.6-2 Electrons Electrons carried carried via NADH and via NADH FADH2 Pyruvate Glycolysis Citric oxidation acid Glucose Pyruvate Acetyl CoA cycle CYTOSOL MITOCHONDRION ATP ATP Substrate-level Substrate-level phosphorylation phosphorylation
  • 26.
    Figure 9.6-3 Electrons Electrons carried carried via NADH and via NADH FADH2 Oxidative Pyruvate Glycolysis Citric phosphorylation: oxidation acid electron transport Glucose Pyruvate Acetyl CoA cycle and chemiosmosis CYTOSOL MITOCHONDRION ATP ATP ATP Substrate-level Substrate-level Oxidative phosphorylation phosphorylation phosphorylation
  • 27.
    • The processthat generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions © 2011 Pearson Education, Inc.
  • 28.
    • Oxidative phosphorylationaccounts for almost 90% of the ATP generated by cellular respiration • A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation • For each molecule of glucose degraded to CO2 and water by respiration, the cell makes up to 32 molecules of ATP © 2011 Pearson Education, Inc.
  • 29.
    Figure 9.7 Enzyme Enzyme ADP P Substrate ATP Product
  • 30.
    Concept 9.2: Glycolysisharvests chemical energy by oxidizing glucose to pyruvate • Glycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvate • Glycolysis occurs in the cytoplasm and has two major phases – Energy investment phase – Energy payoff phase • Glycolysis occurs whether or not O2 is present © 2011 Pearson Education, Inc.
  • 31.
    Figure 9.8 Energy Investment Phase Glucose 2 ADP + 2 P 2 ATP used Energy Payoff Phase 4 ADP + 4 P 4 ATP formed 2 NAD+ + 4 e− + 4 H+ 2 NADH + 2 H+ 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+
  • 32.
    Figure 9.9-1 Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate ADP Hexokinase 1
  • 33.
    Figure 9.9-2 Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate Fructose 6-phosphate ADP Hexokinase Phosphogluco- isomerase 1 2
  • 34.
    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- Phospho- isomerase fructokinase 1 2 3
  • 35.
    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- Phospho- isomerase fructokinase 1 2 3 Aldolase 4 Dihydroxyacetone Glyceraldehyde phosphate 3-phosphate To Isomerase 5 step 6
  • 36.
    Figure 9.9-5 Glycolysis: Energy Payoff Phase 2 NADH 2 NAD+ + 2 H+ Triose phosphate 2Pi dehydrogenase 1,3-Bisphospho- 6 glycerate
  • 37.
    Figure 9.9-6 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD+ + 2 H+ 2 ADP 2 Triose Phospho- phosphate 2Pi glycerokinase dehydrogenase 1,3-Bisphospho- 7 3-Phospho- 6 glycerate glycerate
  • 38.
    Figure 9.9-7 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD+ + 2 H+ 2 ADP 2 2 Triose Phospho- Phospho- phosphate glyceromutase 2Pi glycerokinase dehydrogenase 1,3-Bisphospho- 7 3-Phospho- 8 2-Phospho- 6 glycerate glycerate glycerate
  • 39.
    Figure 9.9-8 Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 H2O 2 NAD+ + 2 H+ 2 ADP 2 2 2 Triose Phospho- Phospho- Enolase phosphate glyceromutase 2Pi glycerokinase dehydrogenase 9 1,3-Bisphospho- 7 3-Phospho- 8 2-Phospho- Phosphoenol- 6 glycerate glycerate glycerate pyruvate (PEP)
  • 40.
    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 Phospho- Phospho- Enolase Pyruvate phosphate glyceromutase kinase 2Pi glycerokinase dehydrogenase 9 1,3-Bisphospho- 7 3-Phospho- 8 2-Phospho- Phosphoenol- 10 Pyruvate 6 glycerate glycerate glycerate pyruvate (PEP)
  • 41.
    Figure 9.9a Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate Fructose 6-phosphate ADP Hexokinase Phosphogluco- isomerase 1 2
  • 42.
    Figure 9.9b Glycolysis: Energy Investment Phase ATP Fructose 6-phosphate Fructose 1,6-bisphosphate ADP Phospho- fructokinase Aldolase 4 3 Dihydroxyacetone Glyceraldehyde phosphate 3-phosphate To Isomerase 5 step 6
  • 43.
    Figure 9.9c Glycolysis: Energy Payoff Phase 2 ATP 2 NADH 2 NAD+ + 2 H+ 2 ADP 2 2 Triose Phospho- phosphate 2Pi glycerokinase dehydrogenase 1,3-Bisphospho- 7 3-Phospho- 6 glycerate glycerate
  • 44.
    Figure 9.9d Glycolysis: Energy Payoff Phase 2 ATP 2 H2O 2 ADP 2 2 2 2 Phospho- Enolase Pyruvate glyceromutase kinase 9 3-Phospho- 8 2-Phospho- Phosphoenol- 10 Pyruvate glycerate glycerate pyruvate (PEP)
  • 45.
    Concept 9.3: Afterpyruvate is oxidized, the citric acid cycle completes the energy- yielding oxidation of organic molecules • In the presence of O2, pyruvate enters the mitochondrion (in eukaryotic cells) where the oxidation of glucose is completed © 2011 Pearson Education, Inc.
  • 46.
    Oxidation of Pyruvateto Acetyl CoA • Before the citric acid cycle can begin, pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle • This step is carried out by a multienzyme complex that catalyses three reactions © 2011 Pearson Education, Inc.
  • 47.
    Figure 9.10 MITOCHONDRION CYTOSOL CO2 Coenzyme A 1 3 2 NAD+ NADH + H+ Acetyl CoA Pyruvate Transport protein
  • 48.
    The Citric AcidCycle • The citric acid cycle, also called the Krebs cycle, completes the break down of pyrvate to CO2 • The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn © 2011 Pearson Education, Inc.
  • 49.
    Figure 9.11 Pyruvate CO2 NAD + CoA NADH + H+ Acetyl CoA CoA CoA Citric acid cycle 2 CO2 FADH2 3 NAD+ FAD 3 NADH + 3 H+ ADP + P i ATP
  • 50.
    • The citricacid cycle has eight steps, each catalyzed by a specific enzyme • The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate • The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle • The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain © 2011 Pearson Education, Inc.
  • 51.
    Figure 9.12-1 Acetyl CoA CoA-SH 1 Oxaloacetate Citrate Citric acid cycle
  • 52.
    Figure 9.12-2 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate Citric acid cycle
  • 53.
    Figure 9.12-3 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric 3 NADH acid + H+ cycle CO2 α-Ketoglutarate
  • 54.
    Figure 9.12-4 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric 3 NADH acid + H+ cycle CO2 CoA-SH α-Ketoglutarate 4 CO2 NAD+ NADH Succinyl + H+ CoA
  • 55.
    Figure 9.12-5 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric 3 NADH acid + H+ cycle CO2 CoA-SH α-Ketoglutarate 4 CoA-SH 5 CO2 NAD+ Succinate Pi NADH GTP GDP Succinyl + H+ CoA ADP ATP
  • 56.
    Figure 9.12-6 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric 3 NADH acid + H+ cycle CO2 Fumarate CoA-SH α-Ketoglutarate 6 4 CoA-SH FADH2 5 CO2 NAD+ FAD Succinate Pi NADH GTP GDP Succinyl + H+ CoA ADP ATP
  • 57.
    Figure 9.12-7 Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric 3 NADH 7 acid + H+ H2 O cycle CO2 Fumarate CoA-SH α-Ketoglutarate 6 4 CoA-SH FADH2 5 CO2 NAD+ FAD Succinate Pi NADH GTP GDP Succinyl + H+ CoA ADP ATP
  • 58.
    Figure 9.12-8 Acetyl CoA CoA-SH NADH + H+ 1 H2O NAD+ 8 Oxaloacetate 2 Malate Citrate Isocitrate NAD+ Citric 3 NADH 7 acid + H+ H2 O cycle CO2 Fumarate CoA-SH α-Ketoglutarate 6 4 CoA-SH FADH2 5 CO2 NAD+ FAD Succinate Pi NADH GTP GDP Succinyl + H+ CoA ADP ATP
  • 59.
    Figure 9.12a Acetyl CoA CoA-SH 1 H2O Oxaloacetate 2 Citrate Isocitrate
  • 60.
    Figure 9.12b Isocitrate NAD+ NADH 3 + H+ CO2 CoA-SH α-Ketoglutarate 4 CO2 NAD+ NADH Succinyl + H+ CoA
  • 61.
    Figure 9.12c Fumarate 6 CoA-SH FADH2 5 FAD Succinate Pi GTP GDP Succinyl CoA ADP ATP
  • 62.
    Figure 9.12d NADH + H+ NAD+ 8 Oxaloacetate Malate 7 H2O Fumarate
  • 63.
    Concept 9.4: Duringoxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis • Following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the energy extracted from food • These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation © 2011 Pearson Education, Inc.
  • 64.
    The Pathway ofElectron Transport • The electron transport chain is 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 • Electrons drop in free energy as they go down the chain and are finally passed to O2, forming H2O © 2011 Pearson Education, Inc.
  • 65.
    Figure 9.13 NADH 50 2 e− NAD+ FADH2 2 e− FAD Multiprotein Free energy (G) relative to O2 (kcal/mol) 40 FMN I complexes Fe• S II Fe• S Q III Cyt b Fe• S 30 Cyt c1 IV Cyt c Cyt a Cyt a3 20 2 e− 10 (originally from NADH or FADH2) 0 2 H+ + 1/2 O2 H2O
  • 66.
    • Electrons aretransferred from NADH or FADH2 to the electron transport chain • Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O2 • The electron transport chain generates no ATP directly • It breaks the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts © 2011 Pearson Education, Inc.
  • 67.
    Chemiosmosis: The Energy-Coupling Mechanism • Electron transfer in the electron transport chain causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space • 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 • This is an example of chemiosmosis, the use of energy in a H+ gradient to drive cellular work © 2011 Pearson Education, Inc.
  • 68.
    Figure 9.14 INTERMEMBRANE SPACE H+ Stator Rotor Internal rod Catalytic knob ADP + Pi ATP MITOCHONDRIAL MATRIX
  • 69.
    Figure 9.15 H+ H + Protein H + complex H+ Cyt c of electron carriers IV Q III I ATP II synth- 2 H+ + 1/2O2 H2O ase FADH2 FAD NADH NAD+ ADP + P i ATP (carrying electrons from food) H+ 1 Electron transport chain 2 Chemiosmosis Oxidative phosphorylation
  • 70.
    • The energystored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis • The H+ gradient is referred to as a proton- motive force, emphasizing its capacity to do work © 2011 Pearson Education, Inc.
  • 71.
    An Accounting ofATP 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 ATP • There are several reasons why the number of ATP is not known exactly © 2011 Pearson Education, Inc.
  • 72.
    Figure 9.16 Electron shuttles MITOCHONDRION span membrane 2 NADH or 2 FADH2 2 NADH 2 NADH 6 NADH 2 FADH2 Glycolysis Pyruvate oxidation Oxidative Citric phosphorylation: Glucose 2 Pyruvate 2 Acetyl CoA acid electron transport cycle and chemiosmosis + 2 ATP + 2 ATP + about 26 or 28 ATP About Maximum per glucose: 30 or 32 ATP CYTOSOL
  • 73.
    Concept 9.5: Fermentationand anaerobic respiration enable cells to produce ATP without the use of oxygen • Most cellular respiration requires O2 to produce ATP • Without O2, the electron transport chain will cease to operate • In that case, glycolysis couples with fermentation or anaerobic respiration to produce ATP © 2011 Pearson Education, Inc.
  • 74.
    • Anaerobic respirationuses an electron transport chain with a final electron acceptor other than O2, for example sulfate • Fermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP © 2011 Pearson Education, Inc.
  • 75.
    Types of Fermentation • Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis • Two common types are alcohol fermentation and lactic acid fermentation © 2011 Pearson Education, Inc.
  • 76.
    • In alcoholfermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO2 • Alcohol fermentation by yeast is used in brewing, winemaking, and baking © 2011 Pearson Education, Inc.
  • 77.
    Figure 9.17 2 ADP + 2 P 2 ATP 2 ADP + 2 P 2 ATP i i 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 (b) Lactic acid fermentation
  • 78.
    Figure 9.17a 2 ADP + 2 P i 2 ATP Glucose Glycolysis 2 Pyruvate 2 NAD + 2 NADH 2 CO2 + 2 H+ 2 Ethanol 2 Acetaldehyde (a) Alcohol fermentation
  • 79.
    • In lacticacid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2 • Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt • Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce © 2011 Pearson Education, Inc.
  • 80.
    Figure 9.17b 2 ADP + 2 P i 2 ATP Glucose Glycolysis 2 NAD + 2 NADH + 2 H+ 2 Pyruvate 2 Lactate (b) Lactic acid fermentation
  • 81.
    Comparing Fermentation withAnaerobic and 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 © 2011 Pearson Education, Inc.
  • 82.
    • Obligate anaerobescarry out fermentation or anaerobic respiration and cannot survive in the presence of O2 • Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration • In a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes © 2011 Pearson Education, Inc.

Editor's Notes

  • #3 For the Discovery Video Space Plants, go to Animation and Video Files.
  • #4 Figure 9.1 How do these leaves power the work of life for this chimpanzee?
  • #6 Figure 9.2 Energy flow and chemical recycling in ecosystems.
  • #12 Figure 9.UN01 In-text figure, p. 164
  • #13 Figure 9.UN02 In-text figure, p. 164
  • #15 Figure 9.3 Methane combustion as an energy-yielding redox reaction.
  • #17 Figure 9.UN03 In-text figure, p. 165
  • #19 Figure 9.4 NAD  as an electron shuttle.
  • #20 Figure 9.UN04 In-text figure, p. 166
  • #22 Figure 9.5 An introduction to electron transport chains.
  • #24 Figure 9.UN05 In-text figure, p. 167
  • #25 Figure 9.6 An overview of cellular respiration.
  • #26 Figure 9.6 An overview of cellular respiration.
  • #27 Figure 9.6 An overview of cellular respiration.
  • #30 Figure 9.7 Substrate-level phosphorylation.
  • #32 Figure 9.8 The energy input and output of glycolysis.
  • #33 Figure 9.9 A closer look at glycolysis.
  • #34 Figure 9.9 A closer look at glycolysis.
  • #35 Figure 9.9 A closer look at glycolysis.
  • #36 Figure 9.9 A closer look at glycolysis.
  • #37 Figure 9.9 A closer look at glycolysis.
  • #38 Figure 9.9 A closer look at glycolysis.
  • #39 Figure 9.9 A closer look at glycolysis.
  • #40 Figure 9.9 A closer look at glycolysis.
  • #41 Figure 9.9 A closer look at glycolysis.
  • #42 Figure 9.9 A closer look at glycolysis. Figure 9.9 A closer look at glycolysis.
  • #43 Figure 9.9 A closer look at glycolysis.
  • #44 Figure 9.9 A closer look at glycolysis.
  • #45 Figure 9.9 A closer look at glycolysis.
  • #48 Figure 9.10 Oxidation of pyruvate to acetyl CoA, the step before the citric acid cycle.
  • #50 Figure 9.11 An overview of pyruvate oxidation and the citric acid cycle.
  • #52 Figure 9.12 A closer look at the citric acid cycle.
  • #53 Figure 9.12 A closer look at the citric acid cycle.
  • #54 Figure 9.12 A closer look at the citric acid cycle.
  • #55 Figure 9.12 A closer look at the citric acid cycle.
  • #56 Figure 9.12 A closer look at the citric acid cycle.
  • #57 Figure 9.12 A closer look at the citric acid cycle.
  • #58 Figure 9.12 A closer look at the citric acid cycle.
  • #59 Figure 9.12 A closer look at the citric acid cycle.
  • #60 Figure 9.12 A closer look at the citric acid cycle.
  • #61 Figure 9.12 A closer look at the citric acid cycle.
  • #62 Figure 9.12 A closer look at the citric acid cycle.
  • #63 Figure 9.12 A closer look at the citric acid cycle.
  • #64 For the Cell Biology Video ATP Synthase 3D Structure — Side View, go to Animation and Video Files. For the Cell Biology Video ATP Synthase 3D Structure — Top View, go to Animation and Video Files.
  • #66 Figure 9.13 Free-energy change during electron transport.
  • #69 Figure 9.14 ATP synthase, a molecular mill.
  • #70 Figure 9.15 Chemiosmosis couples the electron transport chain to ATP synthesis.
  • #73 Figure 9.16 ATP yield per molecule of glucose at each stage of cellular respiration.
  • #78 Figure 9.17 Fermentation.
  • #79 Figure 9.17 Fermentation.
  • #81 Figure 9.17 Fermentation.