Chapter 9 Cellular Respiration: Harvesting Chemical Energy PowerPoint 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 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Overview: Life Is Work Living cells require energy from outside sources Some animals, such as the giant panda, obtain energy by eating plants, and some animals feed on other organisms that eat plants Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-1
Energy flows into an ecosystem as sunlight and leaves as heat Photosynthesis generates O and organic molecules, which are used in cellular respiration Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9- Light energy ECOSYSTEM CO + H O Photosynthesis in chloroplasts Cellular respiration in mitochondria Organic molecules + O ATP ATP powers 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 Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Catabolic Pathways and Production of ATP The breakdown of organic molecules is exergonic Fermentation is a partial degradation of sugars that occurs without O Aerobic respiration consumes organic molecules and O and yields ATP Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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 1 O 6 + 6 O 6 CO + 6 H O + Energy (ATP + heat) Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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 Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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) Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-UN1 becomes oxidized (loses electron) becomes reduced (gains electron)
Fig. 9-UN 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 O Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-3 Reactants becomes oxidized Products becomes reduced Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxide Water
Oxidation of Organic Fuel Molecules During Cellular Respiration During cellular respiration, the fuel (such as glucose) is oxidized, and O is reduced: Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-UN3 becomes oxidized becomes reduced
Fig. 9-UN4 Dehydrogenase
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 Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-4 e + H + Dehydrogenase e + H + NADH H + NAD + + [H] Reduction of NAD + Oxidation of NADH + H + Nicotinamide (reduced form) Nicotinamide (oxidized form)
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 O pulls electrons down the chain in an energyyielding tumble The energy yielded is used to regenerate ATP Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-5 H + 1 / O H 1 / O (from food via NADH) H + + e Controlled release of energy for synthesis of ATP Explosive release of heat and light energy 1 / O (a) Uncontrolled reaction (b) Cellular respiration
The Stages of Cellular Respiration: A Preview Cellular respiration 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) Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-6-1 Electrons carried via NADH Glycolysis Glucose Pyruvate Cytosol ATP Substrate-level phosphorylation
Fig. 9-6- Electrons carried via NADH Electrons carried via NADH and FADH Glucose Glycolysis Pyruvate Citric acid cycle Cytosol Mitochondrion ATP Substrate-level phosphorylation ATP Substrate-level phosphorylation
Fig. 9-6-3 Electrons carried via NADH Electrons carried via NADH and FADH Glucose Glycolysis Pyruvate Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis Cytosol Mitochondrion ATP Substrate-level phosphorylation ATP Substrate-level phosphorylation ATP Oxidative phosphorylation
The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions BioFlix: Cellular Respiration Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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 Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-7 Enzyme ADP Enzyme P Substrate + ATP Product
Concept 9.: 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 Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 9-8 Energy investment phase Glucose ADP + P ATP used Energy payoff phase 4 ADP + 4 P 4 ATP formed NAD + + 4 e + 4 H + NADH + H + Pyruvate + H O Net Glucose Pyruvate + H O 4 ATP formed ATP used ATP NAD + + 4 e + 4 H + NADH + H +
Fig. 9-9-1 Glucose ATP 1 Hexokinase ADP Glucose Glucose-6-phosphate ATP 1 Hexokinase ADP Glucose-6-phosphate
Fig. 9-9- Glucose ATP 1 Hexokinase ADP Glucose-6-phosphate Fructose-6-phosphate Phosphoglucoisomerase Glucose-6-phosphate Phosphoglucoisomerase Fructose-6-phosphate
Fig. 9-9-3 Glucose ATP ADP 1 Hexokinase Fructose-6-phosphate Glucose-6-phosphate Phosphoglucoisomerase Fructose-6-phosphate ATP 3 Phosphofructokinase ADP ATP ADP 3 Phosphofructokinase Fructose- 1, 6-bisphosphate Fructose- 1, 6-bisphosphate
Fig. 9-9-4 Glucose ATP 1 Hexokinase ADP Glucose-6-phosphate Phosphoglucoisomerase Fructose-6-phosphate ATP 3 Phosphofructokinase Fructose- 1, 6-bisphosphate 4 Aldolase ADP 5 Isomerase Fructose- 1, 6-bisphosphate 4 Aldolase 5 Isomerase Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate
Fig. 9-9-5 NAD + NADH + H + 6 Triose phosphate dehydrogenase P i 1, 3-Bisphosphoglycerate Glyceraldehyde- 3-phosphate NAD + NADH + H + 6 Triose phosphate dehydrogenase P i 1, 3-Bisphosphoglycerate
Fig. 9-9-6 NAD + NADH + H + 6 Triose phosphate dehydrogenase P i 1, 3-Bisphosphoglycerate ADP ATP 7 Phosphoglycerokinase 1, 3-Bisphosphoglycerate ADP 3-Phosphoglycerate ATP 7 Phosphoglycerokinase 3-Phosphoglycerate
Fig. 9-9-7 NAD + NADH + H + 6 Triose phosphate dehydrogenase P i 1, 3-Bisphosphoglycerate ADP 7 Phosphoglycerokinase ATP 3-Phosphoglycerate 8 Phosphoglyceromutase 3-Phosphoglycerate -Phosphoglycerate 8 Phosphoglyceromutase -Phosphoglycerate
Fig. 9-9-8 NAD + NADH + H + 6 Triose phosphate dehydrogenase P i 1, 3-Bisphosphoglycerate ADP 7 Phosphoglycerokinase ATP 3-Phosphoglycerate -Phosphoglycerate 8 Phosphoglyceromutase -Phosphoglycerate 9 Enolase H O H O 9 Enolase Phosphoenolpyruvate Phosphoenolpyruvate
Fig. 9-9-9 NAD + NADH + H + 6 Triose phosphate dehydrogenase P i 1, 3-Bisphosphoglycerate ADP 7 Phosphoglycerokinase ATP 3-Phosphoglycerate 8 Phosphoglyceromutase ADP ATP Phosphoenolpyruvate 10 Pyruvate kinase -Phosphoglycerate 9 Enolase H O Phosphoenolpyruvate ADP ATP 10 Pyruvate kinase Pyruvate Pyruvate