Cellular Respiration: Harvesting Chemical Energy

Transcription

1 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

2 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

3 Fig. 9-1

4 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

5 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

6 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

7 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

8 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 O 6 CO + 6 H O + Energy (ATP + heat) Copyright 008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

9 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

10 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

11 Fig. 9-UN1 becomes oxidized (loses electron) becomes reduced (gains electron)

12 Fig. 9-UN becomes oxidized becomes reduced

13 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

14 Fig. 9-3 Reactants becomes oxidized Products becomes reduced Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxide Water

15 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

16 Fig. 9-UN3 becomes oxidized becomes reduced

17 Fig. 9-UN4 Dehydrogenase

18 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

19 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)

20 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

21 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

22 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

23 Fig Electrons carried via NADH Glycolysis Glucose Pyruvate Cytosol ATP Substrate-level phosphorylation

24 Fig 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

25 Fig 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

26 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

27 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

28 Fig. 9-7 Enzyme ADP Enzyme P Substrate + ATP Product

29 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

30 Fig. 9-8 Energy investment phase Glucose ADP + P ATP used Energy payoff phase 4 ADP + 4 P 4 ATP formed NAD e + 4 H + NADH + H + Pyruvate + H O Net Glucose Pyruvate + H O 4 ATP formed ATP used ATP NAD e + 4 H + NADH + H +

31 Fig Glucose ATP 1 Hexokinase ADP Glucose Glucose-6-phosphate ATP 1 Hexokinase ADP Glucose-6-phosphate

32 Fig Glucose ATP 1 Hexokinase ADP Glucose-6-phosphate Fructose-6-phosphate Phosphoglucoisomerase Glucose-6-phosphate Phosphoglucoisomerase Fructose-6-phosphate

33 Fig 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

34 Fig 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

35 Fig 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

36 Fig 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

37 Fig 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

38 Fig 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

39 Fig 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