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Chapter 7 – The Working Cell: Energy from Food

Chapter 7 – The Working Cell: Energy from Food. College Prep Biology Mr. Martino. 7.1 How Cells Make ATP. Cellular Respiration: harvesting of E from food molecules by cells 2 types of respiration: Aerobic: requires oxygen (harvests 40% of E in glucose)

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Chapter 7 – The Working Cell: Energy from Food

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  1. Chapter 7 – The Working Cell: Energy from Food College Prep Biology Mr. Martino

  2. 7.1 How Cells Make ATP • Cellular Respiration: harvesting of E from food molecules by cells • 2 types of respiration: • Aerobic:requires oxygen (harvests 40% of E in glucose) • Anaerobic: does not require oxygen (harvests 2% of E in glucose) • Evolved about 3.8 billion years ago - before oxygen • C6H12O6 + 6 O2 6 CO2 + 6 H2O + E • Glucose is the example carbohydrate

  3. Glycolysis: (exergonic) splits glucose into 2 pyruvic acid • Occurs in cytoplasm • Oxygen is final electron acceptor = water • Enzymes catalyze • First stage of all respiration

  4. Overview of Aerobic Respiration • Aerobic Respiration is continuous – but occurs in 3 main stages • Glycolysis: (exergonic) splits glucose into pyruvic acid • Occurs in cytoplasm • Kreb’s Cycle: (exergonic) completes glucose breakdown - pyruvic acid becomes CO2 • ETC: (endergonic) NADH and FADH2 shuttle e- and generates most of cell’s ATP by chemiosmosis

  5. Two Mechanisms Generate ATP • Chemiosmosis: cells use the potential E of concentration gradients to make ATP • Depends upon membranes and ATP synthase • ETC makes this E transport possible • Cells generate most of their E this way

  6. Substrate-level phosphorylation: an enzyme transfers a P-group from a substrate to ADP • No membrane involved • Only generates a small percentage of a cell’s ATP

  7. 7.3 Second Stage – Pyruvic Acid Conversion and Kreb’s Cycle • 2 pyruvate molecules from glycolysis enter mitochondrion • Pyruvic acid from glycolysis does not enter the Kreb’s cycle • 1. It is oxidized while NAD+ is reduced to NADH • 2. 1 C is released in the form of CO2 • 3. Coenzyme A + fragment = acetyl CoA • Each glucose produces 2 acetyl CoAs for Kreb’s

  8. Kreb’s Cycle • Only the acetyl part of acetyl CoA participates • Each turn of Kreb’s produces: • 1 ATP by substrate level phosphorylation • 3 NADH • 1 FADH2 • Turns twice per glucose

  9. 7.4 Third Stage – Electron Transport System • Final stage of respiration is ETC & ATP formation • The fold of the cristae provide space for many ETC’s and ATP synthases • NADH is shuttled down the e- carriers • Oxygen is the final e- (H) acceptor forming H2O • Proteins shuttle H+ across the membrane • The greater the gradient the more potential E • H+ are passed through ATP synthase which catalyzes the formation of about 34 ATP

  10. 7.5 Anaerobic Respiration • 2 forms of anaerobic respiration • Alcoholic fermentation: anaerobic respiration in which pyruvic acids form ethyl alcohol • Performed by yeasts and bacteria • Releases CO2 • Ethanol is toxic to the organisms who produce it – if too concentrated

  11. 7.5 – con’t • Lactic Acid Fermentation: anaerobic fermentation in which pyruvic acids form lactic acids • Used to make cheese and yogurt • Occurs in muscle cells – causing pain and fatigue • No CO2 is released

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