3a; cellular respiration

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    11-May-2015

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<ul><li>1.Lecture 3a: Cellular Respiration Cellular Respiration</li></ul> <p>2. Cellular Respiration </p> <ul><li>This is the reason you breathe </li></ul> <ul><li>How cells make ATP from carbohydrates </li></ul> <ul><li>Essentially the reverse of photosynthesis </li></ul> <p>3. Helper molecules </p> <ul><li>Coenzymes: nonprotein helpers that move electrons and H around </li></ul> <ul><li>NAD +and FAD +become NADH and FADH </li></ul> <p>4. 4 Phases </p> <ul><li>Glycolysis: Occurs in cytoplasm </li></ul> <ul><li><ul><li>Produces 2 ATP and NADH </li></ul></li></ul> <ul><li><ul><li>Breaks glucose in half into 2 pyruvate </li></ul></li></ul> <ul><li>Prep reaction: Occurs in matrix </li></ul> <ul><li><ul><li>Produces NADH </li></ul></li></ul> <ul><li><ul><li>Breaks pyruvate into 2-carbon acetyl group </li></ul></li></ul> <ul><li><ul><li>Releases CO 2 </li></ul></li></ul> <p>5. 4 Phases </p> <ul><li>Citric acid cycle: occurs in matrix </li></ul> <ul><li><ul><li>Produces more NADH and FADH 2</li></ul></li></ul> <ul><li><ul><li>Releases CO 2</li></ul></li></ul> <ul><li><ul><li>Produces 2 ATP </li></ul></li></ul> <ul><li>Electron transport chain: Occurs in crista </li></ul> <ul><li><ul><li>NADH and FADH 2release electrons</li></ul></li></ul> <ul><li><ul><li>Energy released </li></ul></li></ul> <ul><li><ul><li>Produces water </li></ul></li></ul> <p>6. Glycolysis </p> <ul><li>Occurs outside the mitochondria </li></ul> <ul><li>Uses 2 ATP, but makes 4, so total gain of 2 ATP per glucose broken </li></ul> <ul><li>Makes 2 pyruvate from 1 glucose </li></ul> <p>7. Preparatory Reaction </p> <ul><li>Occurs in matrix of mitochondria </li></ul> <ul><li>Each pyruvate is broken into CO 2and C 2acetyl group, which binds to coenzyme A to produce acetyl CoA </li></ul> <ul><li>NADH is produced </li></ul> <p>8. Citric Acid Cycle </p> <ul><li>Occurs in matrix of mitochondria </li></ul> <ul><li>Acetyl CoA is oxidized to CO2 </li></ul> <ul><li>NADH and FADH2 are produced </li></ul> <ul><li>ATP is produced </li></ul> <p>9. Electron transport chain </p> <ul><li>Occurs in cristae of mitochondria </li></ul> <ul><li>Series of carriers that pass electrons from one to the next </li></ul> <ul><li>NADH and FADH2 are the sources of the electrons, but the chain does not accept the H + , only the e- </li></ul> <ul><li>Final acceptor for electrons is the O 2that we breathe in!</li></ul> <p>10. Electron transport chain </p> <ul><li>Energy released as electrons move down the chain is used to make ATPs </li></ul> <ul><li>NAD and FAD are recycled to be used again </li></ul> <p>11. Electron transport chain </p> <ul><li>What about the H + ? </li></ul> <ul><li>The energy released by the ETC is used to pump H +into the inter-membrane space, between inner and outer membranes of mitochondria </li></ul> <ul><li>This creates a gradient- more H +in inter-membrane space than in matrix </li></ul> <p>12. Electron transport chain </p> <ul><li>Like in photosynthesis, this gradient results in potential energy that can be used </li></ul> <ul><li>ATP synthase exists in cristae </li></ul> <ul><li>H +flows back into matrix through synthase, which makes ATP from the energy </li></ul> <p>13. Electron transport chain </p> <ul><li>Produces 34 ATP from each glucose that originally entered the cycle </li></ul> <ul><li>ETC ATP plus ATP made earlier= 38 ATP per glucose </li></ul> <ul><li>This is about 40% of energy in glucose, the rest is lost as heat </li></ul> <p>14. Fermentation </p> <ul><li>Cellular respiration requires O 2as the final acceptor in the electron transport chain, but what if no O 2is available? </li></ul> <ul><li>Pyruvate is reduced to make lactate, H +comes from NADH </li></ul> <ul><li>Only makes 2 ATP- what is the point? </li></ul> <p>15. Fermentation </p> <ul><li>Regeneration of NAD keeps glycolysis going, instead of stalling (=death) </li></ul> <ul><li>Can create short bursts of energy </li></ul> <ul><li>Why you are sore after strenuous work </li></ul> <ul><li>Yeasts use fermentation and generate ethyl alcohol instead of lactate </li></ul>