Chapter 9 Cellular Respiration Harvesting Chemical Energy Power

Chapter 9 Cellular Respiration: Harvesting Chemical Energy Power. Point® Lecture Presentations for Lectures prepared by Dr. Jorge L. Alonso Florida International University Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Photosynthesis and Respiration

Theme 4: Organisms interact with their environments, exchanging matter and energy Sunlight Ecosystem Photosynthesis Cycling of chemical nutrients Heat Chemical energy Concept 9. 1: Catabolic pathways yield energy by oxidizing organic fuels Respiration Heat

Photosynthesis and Respiration Light energy ECOSYSTEM Photosynthesis in chloroplasts CO 2 + H 2 O C 6 H 12 O 6 + O 2 Cellular respiration in mitochondria Respiration ATP powers most cellular work Heat energy

Catabolic Pathways and Production of ATP • Fermentation is a partial degradation of sugars that occurs without O 2 (anaerobic) to produce a little energy (ATP) and ethanol (or lactate). • Aerobic Respiration is a more complete degradation of sugars that occurs with O 2 and yields much more energy (ATP) and CO 2.

Fermentation is a partial degradation of sugars that occurs without O 2 (anaerobic) to produce a little energy (ATP) and ethanol (or lactate). Alcoholic Fermentation: in Yeast cells, enzymes facilitate production of ethanol. Lactic Acid Fermentation: in animal cells, in the absence of sufficient oxygen, enzymes facilitate production of lactic acid

Other types of Fermentation

Cellular Respiration • 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: C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + Energy (36 ATP + heat) Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Cellular Respiration • It includes both aerobic and anaerobic components, but whole process is refered to as aerobic respiration C 6 H 12 O 6 2 2 2 • C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + Energy (ATP + heat) • The whole process is composed of three major stages 1. Glycolysis 2. Citric Acid (Krebs) Cycle 3. Oxidative Phosphorylation 4 2 Oxidative Phosphorylation 36 6 6

Redox Reactions: Oxidation and Reduction • Chemical reactions in which electrons are transferred between the reactants and release energy e. Energy Oxidation: substance loses electrons, or is oxidized Na Na+ + e- Reducing agent Cl + e- Cl- Oxidizing agent Reduction: substance gains electrons, or is reduced (the amount of positive charge is reduced)

• In redox reactions involving covalent (organic) compounds the electrons are not transferred to produce ions, but a change occurs in the way in which electron are shared in the covalent bonds (1) oxidation: epulled further away, (2) reduction: e- shared closer). becomes oxidized becomes reduced + + 4 - + Carbon: has e- closer + 0 0 Oxygen: has efurther away 2 - 4+ Carbon: has e- further away 2 - + 2 - Oxygen: has ecloser +

How is the energy found in the bonding electrons of Glucose harvested to make ATP during Cellular Respiration? e. How are these electrons Energy transferred to oxygen? • Electrons from organic compounds are usually first transferred to NAD+, an electron-acceptor coenzyme found in cells • Electrons are carried in the form of high energy hydride ions: H- or H: Carbohydrate (reduced) (oxidized) (reduced) • Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP

Nicotinamide Adenine Diphosphate (NAD+ NADH) H H 2 e– + 2 H+ Carbohydrate (reduced) 2 e– + H+ NADH H+ Dehydrogenase NAD+ + 2[H] Reduction of NAD+ + H+ Oxidation of NADH Nicotinamide (reduced form) Nicotinamide (oxidized form)

How are electrons and their energy harvested from Glucose? • NADH and FADH 2 gather electrons (H-) at different stages of respiration and passes them to the electron transport chain. C 6 H 12 O 6 2 2 2 • The electron transport chain passes energetic electrons to O 2 in a series of enzymatically controlled steps (instead of one explosive reaction) • O 2 pulls electrons down the chain in an energy-yielding tumble and H 2 O is produced. 4 (H-) • The energy yielded is used to regenerate ATP (oxidative phosphorylation) 2 Oxidative Phosphorylation 36 6 6

• The electron transport chain passes energetic electrons to O 2 in a series of enzymatically controlled steps (instead of one explosive reaction) ort Free energy, G Explosive release of heat and light energy + 2 H (from glucose via NADH) Controlled release of + – 2 H + 2 e energy for synthesis of ATP sp tran tron Elec chain Free energy, G H 2 + 1 / 2 O 2 ATP 2 e– 2 1/ H+ H 2 O (a) Uncontrolled reaction 1/ H 2 O (b) Cellular respiration 2 O 2

The Stages of Cellular Respiration: 1. Glycolysis (breaks down 2. glucose into two molecules of pyruvate), some ATP and NADH produced Electrons carried via NADH Glycolysis Pyruvate Glucose Cytosol ATP Substrate-level phosphorylation The Citric Acid (Krebs) Cycle (breaks down pyruvate into CO 2), producing some ATP, NADH and FADH 2

The Stages of Cellular Respiration: 1. Glycolysis (breaks down 2. glucose into two molecules of pyruvate), some ATP and NADH produced The Citric Acid (Krebs) 3. Cycle (breaks down pyruvate into CO 2), producing some ATP, NADH and FADH 2 Electrons carried via NADH Citric acid cycle Glycolysis Pyruvate Glucose Oxidative Phosphorylation (uses H 2 O to oxidize the NADH & FADH 2 produced in previous steps, producing O 2 and lots of ATP) Mitochondrion Cytosol ATP Substrate-level phosphorylation

The Stages of Cellular Respiration: 1. Glycolysis (breaks down 2. glucose into two molecules of pyruvate), some ATP and NADH produced The Citric Acid (Krebs) 3. Cycle (breaks down pyruvate into CO 2), producing some ATP, NADH and FADH 2 Electrons carried via NADH Citric acid cycle Glycolysis Pyruvate Glucose Oxidative Phosphorylation (uses H 2 O to oxidize the NADH & FADH 2 produced in previous steps, producing O 2 and lots of ATP) Oxidative phosphorylation: (1) Electron transport and (2) chemiosmosis Mitochondrion Cytosol ATP ATP Substrate-level phosphorylation Oxidative phosphorylation

• About 10% of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation Enzyme Substrate-Phosphorylated + ADP Enzyme Product-un. Phosphorylated + ATP Enzyme ADP P Substrate + Product ATP

The process that generates most of the ATP is called oxidative phosphorylation because it Bio. Flix: Cellular Respiration is powered by redox reactions H+ H+ H+ Protein complex of electron carriers Cyt c V Q FADH 2 NADH ATP synthase FAD 2 H+ + 1/2 O 2 NAD+ H 2 O ADP + P i (carrying electrons from food) ATP H+ 1 Electron transport chain • H+ 2 Chemiosmosis This process accounts for almost 90% of the ATP generated by respiration

Concept 9. 2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate • Glycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvate + Glucose 2 Pyruvates • Glycolysis has two major phases: (1)Energy investment phase (2)Energy payoff phase

Glucose ATP 1 Hexokinase ADP Glucose-6 -phosphate

Glucose ATP 1 Hexokinase ADP Glucose-6 -phosphate 2 Phosphoglucoisomerase Fructose-6 -phosphate

Glucose ATP 1 Hexokinase AD P Fructose-6 -phosphate Glucose-6 -phosphate 2 Phosphoglucoisomerase ATP 3 Phosphofructokinase Fructose-6 -phosphate ATP 3 Phosphofructokinase ADP AD P Fructose 1, 6 -bisphosphate

Glucose ATP 1 Hexokinase AD P Glucose-6 -phosphate 2 Phosphoglucoisomerase Fructose 1, 6 -bisphosphate 4 Fructose-6 -phosphate ATP Aldolase 3 Phosphofructokinase AD P 5 Isomerase Fructose 1, 6 -bisphosphate 4 Aldolase 5 Isomerase Dihydroxyacetone phosphate Glyceraldehyde 3 -phosphate

2 NAD+ 2 NADH + 2 H+ 6 Triose phosphate dehydrogenase 2 Pi 2 1, 3 -Bisphoglycerate Glyceraldehyde 3 -phosphate 2 NAD+ 2 NADH 6 Triose phosphate dehydrogenase 2 Pi + 2 H+ 2 1, 3 -Bisphoglycerate

2 NAD+ 2 NADH + 2 H+ 6 Triose phosphate dehydrogenase 2 Pi 2 1, 3 -Bisphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 1, 3 -Bisphoglycerate 2 ADP 2 3 -Phosphoglycerate 2 ATP 2 7 Phosphoglycerokinase 3 -Phosphoglycerate

2 NAD+ 2 NADH + 2 H+ 6 Triose phosphate dehydrogenase 2 Pi 2 1, 3 -Bisphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 3 -Phosphoglycerate 8 2 3 -Phosphoglycerate Phosphoglyceromutase 2 8 Phosphoglyceromutase 2 -Phosphoglycerate 2 2 -Phosphoglycerate

2 NAD+ 2 NADH + 2 H+ 6 Triose phosphate dehydrogenase 2 Pi 2 1, 3 -Bisphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 3 -Phosphoglycerate 2 2 -Phosphoglycerate 8 Phosphoglyceromutase 2 9 2 H 2 O 2 -Phosphoglycerate Enolase 9 2 H 2 O 2 Enolase Phosphoenolpyruvate 2 Phosphoenolpyruvate

2 NAD+ 2 NADH + 2 H+ 6 Triose phosphate dehydrogenase 2 Pi 2 1, 3 -Bisphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 Phosphoenolpyruvate 2 ADP 2 3 -Phosphoglycerate 8 10 Pyruvate kinase Phosphoglyceromutase 2 ATP 2 2 -Phosphoglycerate 9 2 H 2 O Enolase 2 Phosphoenolpyruvate 2 ADP 10 Pyruvate kinase 2 ATP 2 2 Pyruvate

Concept 9. 3: The Citric Acid (Krebs) Cycle completes the energyyielding oxidation of organic molecules C 6 H 12 O 6 2 2 2 • In the presence of O 2, pyruvate enters the mitochondrion • Before the citric acid cycle can begin, pyruvate must be converted to acetyl Co. A, which links the cycle to glycolysis 4 2 Oxidative Phosphorylation 36 6 6

The junction between glycolysis & the citric acid cycle: Conversion of pyruvate to acetyl Co. A • In the presence of O 2, pyruvate enters the mitochondrion, at the cost of an ATP for transport of each pyruvate molecule • Before the citric acid cycle can begin, pyruvate must be converted to acetyl Co. A, which links the cycle to glycolysis CYTOSOL MITOCHONDRION NAD+ NADH + H+ 2 1 Pyruvate Transport protein 3 CO 2 Coenzyme A Acetyl Co. A

The junction between glycolysis & the citric acid cycle: Conversion of pyruvate to acetyl Co. A Enzymes of Glycolysis juction to CAC: 1. Citrate synthase 2. Pyruvate carboxylase

The Citric Acid (Krebs) Cycle Pyruvate CO 2 NAD+ Co. A • The CAC takes place within the mitochondrial matrix • The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH 2 per turn NADH + H+ Acetyl Co. A Citric acid cycle FADH 2 2 CO 2 3 NAD+ 3 NADH FAD + 3 H+ ADP + P i ATP

The Citric Acid (Krebs) Cycle • In the first of eight steps in the CAC, the acetyl group of acetyl Co. A joins the cycle by combining with oxaloacetate, forming citrate. Each step is catalyzed by a specific enzyme Enzymes of CAC: 1. Citrate synthase • The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle Acetyl Co. A—SH 1 Oxaloacetate Citric Acid Cycle

The Citric Acid (Krebs) Cycle Acetyl Co. A—SH H 2 O 1 Oxaloacetate 2 Citrate Isocitrate Enzymes of CAC: 1. Citrate synthase 2. Aconitase Citric Acid Cycle

The Citric Acid (Krebs) Cycle • The NADH and FADH 2 produced by the cycle relay electrons extracted from food to the electron transport chain Enzymes of CAC: 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase Acetyl Co. A—SH 1 H 2 O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric Acid Cycle 3 NADH + H+ CO 2 -Ketoglutarate

The Citric Acid (Krebs) Cycle Acetyl Co. A—SH 1 H 2 O Oxaloacetate 2 Citrate Isocitrate NAD+ Enzymes of CAC: Citric Acid Cycle NADH + H+ 3 CO 2 Co. A—SH 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase 4. ά-ketoglutarate dehydrogenase -Ketoglutarate 4 NAD+ Succinyl Co. A NADH + H+ CO 2

The Citric Acid (Krebs) Cycle Acetyl Co. A—SH 1 H 2 O Oxaloacetate 2 Citrate Isocitrate NAD+ Citric Acid Cycle Enzymes of CAC: NADH + H+ 3 CO 2 Co. A—SH 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase 4. ά-ketoglutarate dehydrogenase 5. Succinyl-Co. A synthetase -Ketoglutarate 4 Co. A—SH 5 NAD+ Succinate GTP GDP ATP Pi Succinyl Co. A NADH + H+ CO 2

The Citric Acid (Krebs) Cycle Acetyl Co. A—SH H 2 O 1 Oxaloacetate 2 Citrate Isocitrate NAD+ Citric Acid Cycle Enzymes of CAC: 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase 4. ά-ketoglutarate dehydrogenase 5. Succinyl-Co. A synthetase 6. Succinate dehydrogenase Fumarate NADH + H+ 3 CO 2 Co. A—SH 6 -Ketoglutarate 4 Co. A—SH 5 FADH 2 NAD+ FAD Succinate GTP GDP ATP Pi Succinyl Co. A NADH + H+ CO 2

The Citric Acid (Krebs) Cycle Acetyl Co. A—SH H 2 O 1 Oxaloacetate 2 Malate Citrate Isocitrate NAD+ H 2 O 7 Enzymes of CAC: 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase 4. ά-ketoglutarate dehydrogenase 5. Succinyl-Co. A synthetase 6. Succinate dehydrogenase 7. Fumarase Citric Acid Cycle Fumarate NADH + H+ 3 CO 2 Co. A—SH 6 -Ketoglutarate 4 Co. A—SH 5 FADH 2 NAD+ FAD Succinate GTP GDP ATP Pi Succinyl Co. A NADH + H+ CO 2

The Citric Acid (Krebs) Cycle Acetyl Co. A—SH NADH +H+ H 2 O 1 NAD+ 8 Oxaloacetate 2 Malate Citrate Isocitrate NAD+ H 2 O 7 Enzymes of CAC: 1. Citrate synthase 2. Aconitase 3. Isocirate dehydrogenase 4. ά-ketoglutarate dehydrogenase 5. Succinyl-Co. A synthetase 6. Succinate dehydrogenase 7. Fumarase 8. Malate dehydrogenase Citric Acid Cycle Fumarate NADH + H+ 3 CO 2 Co. A—SH 6 -Ketoglutarate 4 Co. A—SH 5 FADH 2 NAD+ FAD Succinate GTP GDP ATP Pi Succinyl Co. A NADH + H+ CO 2

Power. Point® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Concept 9. 4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis C 6 H 12 O 6 2 2 2 • Following glycolysis and the citric acid cycle, NADH and FADH 2 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 4 2 Oxidative Phosphorylation 36 6 6

Oxidative Phosphorylation • The Enzymes for Oxidative Phosphorylation are located in the inner membrane of the cristae in the mitochondrion. • Most of the chain’s components are proteins, which exist in multiprotein complexes • Oxidative Phosphorylation is composed of two separate processes: 1. Electron Transport Chain, which uses the energy in electrons to pump H+ ions from the matrix to the intermembrane space. {ETC 1} 2. Chemosmosis, which uses the osmotic pressure from now concentrated H+ ions to energize ATP {Chm. Osmo} Glycolysis INTERMEMBRANE SPACE Krebs Cycle MITOCHONDIRAL MATRIX

The Pathway of Electron Transport NADH 50 • Electrons are transferred from NADH or FADH 2 to the electron transport chain • 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 O 2, forming H 2 O • The electron transport chain generates no ATP NAD+ FADH 2 2 e– 40 Free energy (G) relative to O 2 (kcal/mol) • Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O 2 2 e– FMN FAD Multiprotein complexes FAD Fe • S Q Cyt b 30 Fe • S Cyt c 1 IV Cyt c Cyt a 20 10 0 Cyt a 3 2 e– (from NADH or FADH 2) 2 H+ + 1/2 O 2 H 2 O

The Pathway of Electron Transport • 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 channels in 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 INTERMEMBRANE SPACE MITOCHONDIRAL MATRIX

ATP synthase, a molecular mill INTERMEMBRANE SPACE • The energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis • The gradient is referred to as a proton-motive force, emphasizing its capacity to do work H+ H+ Stator Rotor Internal rod Catalytic knob ADP + P i ATP MITOCHONDRIAL MATRIX

EXPERIMENT Magnetic bead Electromagnet Sample Internal rod Catalytic knob Nickel plate RESULTS Rotation in one direction Rotation in opposite direction Number of photons detected ( 103) Fig. 9 -15 No rotation 30 25 20 0 Sequential trials

Fig. 9 -15 a EXPERIMENT Magnetic bead Electromagnet Sample Internal rod Catalytic knob Nickel plate

Fig. 9 -15 b Number of photons detected (x 103) RESULTS Rotation in one direction Rotation in opposite direction No rotation 30 25 20 0 Sequential trials

Fig. 9 -16 H+ H+ H+ Protein complex of electron carriers H+ Cyt c V Q FADH 2 NADH ATP synthase FAD 2 H+ + 1/2 O 2 NAD+ H 2 O ADP + P i (carrying electrons from food) ATP H+ 1 Electron transport chain Oxidative phosphorylation 2 Chemiosmosis

ATP Production by Cellular Respiration • During cellular respiration, most energy flows in this sequence: glucose NADH electron transport chain proton-motive force ATP • About 40% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 38 ATP

Concept 9. 5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen C 6 H 12 O 6 2 2 2 • Most cellular respiration requires O 2 to produce ATP • Glycolysis can produce ATP with or without O 2 (in aerobic or anaerobic conditions) • In the absence of O 2, glycolysis couples with fermentation or anaerobic respiration to produce ATP 4 2 Oxidative Phosphorylation 36 6 6

• Anaerobic respiration uses an electron transport chain with an electron acceptor other than O 2, for example sulfate • Fermentation uses phosphorylation instead of an electron transport chain to generate ATP Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Types of Fermentation Animation: Fermentation Overview 2 ADP + 2 Pi • Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis Glucose Two common types are alcohol fermentation and lactic acid fermentation • In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO 2 Alcohol fermentation by yeast is used in brewing, winemaking, and baking • In lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO 2 • 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 O 2 is scarce Glycolysis 2 Pyruvate • • 2 ATP 2 NAD+ 2 NADH + 2 H+ 2 CO 2 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 ADP + 2 Pi Glucose 2 ATP Glycolysis 2 NAD+ 2 Lactate (b) Lactic acid fermentation 2 NADH + 2 H+ 2 Pyruvate

Fermentation and Aerobic Respiration Compared • Both processes use glycolysis to oxidize glucose and other organic fuels to pyruvate C 6 H 12 O 6 2 2 2 • The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O 2 in cellular respiration • Cellular respiration produces 38 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule 4 2 Oxidative Phosphorylation 36 6 6

• Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O 2 • 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 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 9 -19 Glucose CYTOSOL Glycolysis Pyruvate No O 2 present: Fermentation O 2 present: Aerobic cellular respiration MITOCHONDRION Ethanol or lactate Acetyl Co. A Citric acid cycle

The Evolutionary Significance of Glycolysis • Glycolysis occurs in nearly all organisms • Glycolysis probably evolved in ancient prokaryotes before there was oxygen in the atmosphere Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Concept 9. 6: Glycolysis and the citric acid cycle connect to many other metabolic pathways • Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways • Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose: Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Versatility of Catabolism Proteins • Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration Amino acids • Fats are digested to glycerol (used in glycolysis) and fatty acids (used in generating acetyl Co. A) • Fatty acids are broken down by beta oxidation and yield acetyl Co. A • An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate Sugars Glycolysis • Glycolysis accepts a wide range of carbohydrates • Proteins must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycle Carbohydrates Glucose Glyceraldehyde-3 - P NH 3 Pyruvate Acetyl Co. A Citric acid cycle Oxidative phosphorylation Fats Glycerol Fatty acids

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 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Regulation of Cellular Respiration via Feedback Mechanisms • Feedback inhibition is the most common mechanism for control • If ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down • Control of catabolism is based mainly on regulating the activity of enzymes at strategic points in the catabolic pathway Glucose Glycolysis Fructose-6 -phosphate – AMP Stimulates + Phosphofructokinase – Fructose-1, 6 -bisphosphate Inhibits Pyruvate ATP Citrate Acetyl Co. A Citric acid cycle Oxidative phosphorylation

Fig. 9 -UN 5 Outputs Inputs 2 Glycolysis ATP + 2 NADH Glucose 2 Pyruvate

Fig. 9 -UN 6 Inputs Outputs S—Co. A C 2 ATP O CH 3 2 Acetyl Co. A 6 NADH O C COO CH 2 COO 2 Oxaloacetate Citric acid cycle 2 FADH 2

Fig. 9 -UN 7 INTERMEMBRANE SPACE H+ ATP synthase ADP + P i MITOCHONDRIAL MATRIX ATP H+

p. H difference across membrane Fig. 9 -UN 8 Time

Fig. 9 -UN 9

You should now be able to: 1. Explain in general terms how redox reactions are involved in energy exchanges 2. Name three stages of cellular respiration; for each, state the region of the eukaryotic cell where it occurs and the products that result 3. In general terms, explain the role of the electron transport chain in cellular respiration Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

4. Explain where and how the respiratory electron transport chain creates a proton gradient 5. Distinguish between fermentation and anaerobic respiration 6. Distinguish between obligate and facultative anaerobes Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings