1. 1 Cellular Respiration and Fermentation Chapter 7, Sections 5 and 6

2. 2 The Cellular isms Metabolism: is the set of chemical reactions that occur in living organisms in order to maintain life. – These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. – Usually divided into two categories. Catabolism and Anabolism − Catabolism: breaking down & releasing energy − Anabolism: building up & requires energy

3. 3 A Metabolic Pathway called Cellular Respiration Cells harvest energy by breaking bonds and shifting electrons from one molecule to another. – aerobic respiration - final electron acceptor is oxygen – anaerobic respiration - final electron acceptor is a molecule other than oxygen

4. 4 Aerobic Respiration Occurs in 3 Stages: 1. Glycolysis 2. The Kreb’s Cycle 3. Electron Transport Chain and ATP Synthase

5. 5 Stage One - Glycolysis Occurs in the cytoplasm For each molecule of glucose that passes through glycolysis, the cell nets 2 ATP molecules and 2 pyruvic acid molecules NADH carries 2 high energy electrons Glucose →2 Pyruvic Acid 2 NADH 2 ATP

6. 6 Stage Two – The Kreb’s Cycle Occurs in the matrix of the mitochondrion where the needed enzymes are dissolved As pyruvic acid diffuses into the mitochondrion, each 3C molecule loses a molecule of CO 2 and is converted into acetyl coenzyme A, or acetyl CoA Glucose →2 Pyruvic Acid 2 NADH 2 ATP 2 Acetyl CoA 1 NADH 2 CO 2

7. 7 Stage Two – The Kreb’s Cycle (con’t) Acetyl CoA is oxidized in a series of reactions Named after biologist Hans Krebs who first explained the steps in the 1930s

8. 8 6-carbon Molecule 5-carbon Molecule 4-carbon Acceptor Stage Two – The Kreb’s Cycle (con’t) KREB’S CYCLE CO 2 Acetyl CoA 3 NADH + 1 FADH 2 After 2 cycles, 6 NADH, 2 FADH 2, 4 CO 2, and 2 ATP molecules are produced ATP

9. 9 Stage Three: The Electron Transport Chain NADH molecules carry electrons to the inner mitochondrial membrane, where they transfer electrons to a series of membrane- associated proteins (electron carriers). Eventually the electrons are pulled towards OXYGEN and combine with hydrogen ions, forming water

10. 10 Stage Three: ATP Synthase Action The ATP released in the ETC is used to move H+ ions across the membrane from low to high concentrations This stores potential energy (positive side vs negative side) ATP synthase is a protein in the membrane that spins like a mini turbine as H+ ions flow back across the membrane The spinning ATP synthase generates 32-34 ATP molecules from ADP per original glucose molecule

11. 11 ATP Synthase

12. 12 Adding up the ATP from Cellular Respiration Mitochondrion Glycolysis Glucose 2 Pyruvic acid 2 Acetyl- CoA Krebs Cycle Electron Transport Maximum ATP per glucose: ATP Synthase

13. 13 Harvesting Energy WITHOUT Oxygen If oxygen is not available to capture the 2 low energy electrons at the end of the ETC, the Kreb’s cycle and the ETC will stop producing ATP Glycolysis will continue to generate 2 ATP molcules, 2 NADH, and 2 Pyruvic Acid molecules NADH reacts with the pyruvic acid, making NAD+ available to carry electrons so glycolysis can continue making ATP

14. 14 Two Types of Fermentation ALCOHOLIC Pyruvic Acid → CO 2 + ethyl alcohol Occurs in yeast CO 2 makes dough rise and bubbles in beer & champagne Ethyl alcohol makes alcoholic beverages LACTIC ACID Pyruvic Acid → Lactic Acid Occurs in muscles during vigorous exercise (can feel “burn”) Occurs in prokaryotes used to make cheese, yogurt, sour cream, and sauerkraut