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Unraveling Cellular Respiration: From Food to Energy Production

Explore the intricate process of cellular respiration, from the initial steps like glycolysis to the complex Krebs Cycle and Electron Transport Chain, all converging to produce ATP for energy. Understand how this vital process occurs in the presence of oxygen and compare it to photosynthesis. Discover the three sources of ATP generation in the body and the distinction between quick and long-term energy supply. Witness the transformation of food molecules into usable energy and the essential role of oxygen in this crucial biochemical pathway.

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Unraveling Cellular Respiration: From Food to Energy Production

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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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