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Chapter 9

Chapter 9. CELLULAR RESPIRATION. 9-1 Chemical Pathways. Where do we get our E from? Food! Food gives us: Ability to grow/reproduce Raw materials E needed to “use” these materials. Chemical E and Food. Calorie: amount of E needed to raise 1g of water 1°C

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Chapter 9

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  1. Chapter 9 CELLULAR RESPIRATION

  2. 9-1 Chemical Pathways • Where do we get our E from? • Food! • Food gives us: • Ability to grow/reproduce • Raw materials • E needed to “use” these materials

  3. Chemical E and Food • Calorie: amount of E needed to raise 1g of water 1°C • “calorie” on food labels = kilocalorie • 1 kilocalorie = 1000 calories • Cells release E stored in food • Starts with process called “glycolysis” • “glyco” = sugar • “lysis” = split

  4. Cellular Respiration • Releases E by breaking down glucose and other food molecules in the presence of O2 • 6O2 + C6H12O6 = 6CO2 + 6H2O + E • Look familiar? • Happens in gradual steps • Traps E in ATP

  5. Glycolysis • 1st step of cellular respiration • Happens in cytoplasm • GOAL: 1 glucose converted to 2 pyruvic acid • ATP production • NADH production- accepts electrons/E • Starts as NAD+ • Just like NADPH in photosynthesis!

  6. Glycolysis • E yield is small but occurs fast so LOTS of ATP can be made • No need for O2 • When all NAD+ filled with electrons (making NADH), ATP production pauses • When do you think it will start again? • When more NAD+ is available!

  7. Now what? • If O2 is present, move on with cell respiration • If no O2 present...FERMENTATION! • Fermentation: releases E in food by producing ATP without O2

  8. Fermentation • NADH is converted back to NAD+ • If more NAD+, ATP production can continue • “anaerobic” process- no O2 needed Fermentation!

  9. Fermentation(creating more NAD+) • 1. Alcoholic fermentation • Pyruvic acid + NADH = alcohol + CO2 + NAD+ • ex: yeasts, bread dough • 2. Lactic acid fermentation • Pyruvic acid + NADH = lactic acid + NAD+ • ex: muscle cells, food/beverages

  10. 9-2 Krebs Cycle and Electron Transport Chain • At end of glycolysis, 90% of E is still unused • Stored in pyruvic acid • MUST have O2 (aerobic!) • O2 = electron acceptor • When O2 present, pyruvic acid moves to Krebs Cycle

  11. Krebs Cycle • GOAL: Pyruvic acid  CO2 + E • Aka: citric acid cycle (1st compound formed) • Happens in the mitochondria • Occurs in 2 steps

  12. Krebs Cycle Step 1 • Citric acid production • Pyruvic acid  acetyl CoA +CO2 +NADH • CO2 = waste product • NADH = electron/E acceptor • Then Acetyl CoA  citric acid

  13. Krebs Cycle Step 2 • Energy extraction • Citric acid  CO2 +NADH + FADH2 + ATP • + a series of C compounds • E totals: 4 NADH, 1 FADH2, 1 ATP

  14. Products of Krebs Cycle • 1. CO2- released as waste • 2. ATP- E used for cell activities • 3. NADH + FADH2- E carriers • move onto electron transport chain… NADH ATP FADH2

  15. Electron Transport Chain (ETC) • Uses electrons carried from glycolysis and Krebs cycle • NADH and FADH2 • Travel down ETC- lose E • E picked up and used to bring H+ into intermembrane space of mitochondria- buildup

  16. Electron Transport Chain (ETC) • O2 is final electron acceptor in chain • O2 + H+ + electrons = water! • H+ buildup in intermembrane space • Move thru ATP synthase protein • ADP + P  ATP • LOTS of ATP!

  17. Totals: • 36 ATP produced by 1 glucose • Any E not used is released as heat • Why you feel warm after exercise • Waste products = CO2 and water 6O2 + C6H12O6 = 6CO2 + 6H2O + E oxygen carbon dioxide water ATP glucose

  18. Energy and Exercise • 3 places to get ATP • 1. Stored ATP • 2. New ATP from lactic acid fermentation • 3. New ATP from cell resp. • At first, you can use all three • Over time, stored ATP and lactic acid ferm. run out • Then must rely on cell resp. alone

  19. Quick Energy • Used stored ATP (only lasts a few sec) • Then lactic acid ferm. (lasts ~90 sec) • Then you go into O2 debt • Must be “repaid” by heavy breathing

  20. Long-term Energy • Must rely on cell resp. • Slower at supplying ATP but lasts longer (15-20 min) • E stored in muscles as glycogen • After 20 min. the body will breakdown other compounds for E (fats, proteins, etc)

  21. Comparing and Contrasting Photosynthesis and Cell Respiration • Opposite E flows • Photosynthesis provides the food (for plants) • Cell Respiration turns it into E for release

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