1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 9 Cellular Respiration: Harvesting Chemical Energy

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Life Is Work Living cells – Require transfusions of energy from outside sources to perform their many tasks

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The giant panda – Obtains energy for its cells by eating plants Figure 9.1

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Energy – Flows into an ecosystem as sunlight and leaves as heat Light energy ECOSYSTEM CO 2 + H 2 O Photosynthesis in chloroplasts Cellular respiration in mitochondria Organic molecules + O 2 ATP powers most cellular work Heat energy Figure 9.2

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Catabolic Pathways and Production of ATP The breakdown of organic molecules is exergonic (releasing energy)

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings One catabolic process, fermentation – Is a partial degradation of sugars that occurs without oxygen – Aerobic- with oxygen – Anaerobic- without oxygen

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cellular respiration – Is the most common and efficient breakdown of energy from food – Consumes (takes) oxygen and organic molecules such as glucose – Yields (produces) ATP

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings To keep working – Cells must regenerate ATP – ATP- The energy currency for cells to do work (grow, divide, function)

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Redox Reactions: Oxidation and Reduction Catabolic pathways yield energy – Due to the transfer of electrons

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Organic Fuel Molecules During Cellular Respiration During cellular respiration: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Stages of Cellular Respiration: A Preview Respiration is a cumulative function of three metabolic stages – Glycolysis – Krebs cycle (also known as The citric acid cycle) – Electron Transport Chain

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Stages and Locations of Cellular Respiration – Glycolysis (doesn’t require oxygen) happens in the cytoplasm of cell – Krebs cycle/ Citric Acid Cycle (Needs oxygen) happens in the fluid of mitochondria – Electron Transport Chain/ Oxidative phosphorylation (needs oxygen) happens in the mitochondria membrane

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis -> Krebs Cycle -> Electron Transport Chain STEP 1: Glycolysis – Breaks down glucose into two molecules of pyruvate – Glucose --  pyruvate STEP 2: Krebs Cycle/ The citric acid cycle – Completes the breakdown of glucose

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis -> Krebs Cycle -> Electron Transport Chain STEP 3: Electron Transport Chain – Is driven by the electron transport chain – Generates ATP (energy currency)

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An overview of cellular respiration Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH 2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis ATP Substrate-level phosphorylation Oxidative phosphorylation Mitochondrion Cytosol

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 9.2: Glycolysis harvests energy by oxidizing glucose to pyruvate Glycolysis – Means “splitting of sugar” – Breaks down glucose into pyruvate – Occurs in the cytoplasm of the cell Pyruvate ATP Come out Glucose Goes in

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Krebs Cycle/ Citric Acid Cycle The citric acid cycle completes the energy- yielding oxidation of organic molecules The citric acid cycle – Takes place in the matrix of the mitochondrion

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An overview of the citric acid cycle/ Krebs Cycle ATP 2 CO 2 3 NAD + 3 NADH + 3 H + ADP + P i FAD FADH 2 Citric acid cycle CoA Acetyle CoA NADH + 3 H + CoA CO 2 Pyruvate (from glycolysis, 2 molecules per glucose) ATP Glycolysis Citric acid cycle Oxidative phosphorylatio n Figure 9.11 Pyruvate goes in FADH 2 ATP NADH CO 2 Come out

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Electron Transport Chain  ATP synthesis Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis NADH and FADH 2 (Products of Krebs Cycle) – Donate electrons in the electron transport chain which powers ATP synthesis

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings At the end of the Electron Transport Chain – Electrons are passed to oxygen, forming water H2OH2O O2O2 NADH FADH2 FMN FeS O FAD Cyt b Cyt c 1 Cyt c Cyt a Cyt a 3 2 H + + 1  2 I II III IV Multiprotein complexes 0 10 20 30 40 50 Free energy (G) relative to O 2 (kcl/mol) Figure 9.13

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings There are three main processes in this metabolism Electron shuttles span membrane CYTOSOL 2 NADH 2 FADH 2 2 NADH 6 NADH 2 FADH 2 2 NADH Glycolysis Glucose 2 Pyruvate 2 Acetyl CoA Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis MITOCHONDRION by substrate-level phosphorylation by substrate-level phosphorylation by oxidative phosphorylation, depending on which shuttle transports electrons from NADH in cytosol Maximum per glucose: About 36 or 38 ATP + 2 ATP + about 32 or 34 ATP or Figure 9.16

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings There are three main processes in this metabolism SIMPLIFIED! Electron shuttles span membrane CYTOSOL 2 NADH 2 FADH 2 2 NADH 6 NADH 2 FADH 2 2 NADH Glycolysis Glucose 2 Pyruvate Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis MITOCHONDRION Maximum per glucose: About 36 or 38 ATP + 2 ATP + about 32 or 34 ATP or Figure 9.16 2 Acetyl CoA

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings About 40% of the energy in a glucose molecule – Is transferred to ATP during cellular respiration, making between 36-38 ATP

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 9.5: Fermentation- some cells can produce ATP without the use of oxygen – (anaerobic) Cellular respiration – Relies on oxygen to produce ATP Fermentation – Cells can still produce ATP in the absence of Oxygen

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis – Can produce ATP with or without oxygen, in aerobic or anaerobic conditions – Couples with fermentation to produce ATP

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Types of Fermentation Alcohol Fermentation- Happens with yeast Lactic Acid Fermentation- happens in our bodies after exercise.

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In alcohol fermentation – Pyruvate is converted to ethanol in two steps, one of which releases CO 2

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings During lactic acid fermentation – Pyruvate is reduced directly to NADH to form lactate as a waste product

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 2 ADP + 2 P1P1 2 ATP Glycolysis Glucose 2 NAD + 2 NADH 2 Pyruvate 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 ADP + 2 P1P1 2 ATP Glycolysis Glucose 2 NAD + 2 NADH 2 Lactate (b) Lactic acid fermentation H H OH CH 3 C O – O C CO CH 3 H CO O–O– CO CO O CO C OHH CH 3 CO 2 2 Figure 9.17 Alcohol Fermentation -> ethanol Lactic acid Fermentation -> lactic acid

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fermentation and Cellular Respiration Compared Both fermentation and cellular respiration – Use glycolysis to oxidize glucose and other organic fuels to pyruvate

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fermentation vs. Cellular Respiration Cellular respiration – Produces more ATP

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Pyruvate is a key juncture in catabolism (Catabolism is the metabolic breakdown of complex molecules into simpler ones, often resulting in a release of energy.) Glucose CYTOSOL Pyruvate No O 2 present Fermentation O 2 present Cellular respiration Ethanol or lactate Acetyl CoA MITOCHONDRION Citric acid cycle Figure 9.18

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Evolutionary Significance of Glycolysis Glycolysis – Occurs in nearly all organisms – Probably evolved in ancient prokaryotes before there was oxygen in the atmosphere

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Biosynthesis (Anabolic Pathways) The body – Uses small molecules to build other substances These small molecules – May come directly from food or through glycolysis or the citric acid cycle