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Chapter 7 Cellular Respiration

Chapter 7 Cellular Respiration. Section 7.1. Glycolysis and Fermentation. All cells break down complex organic compounds into simpler molecules As the compounds are broken down, cells release energy Some of the energy is used to make ATP from ADP. Harvesting Chemical Energy.

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Chapter 7 Cellular Respiration

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  1. Chapter 7Cellular Respiration Section 7.1

  2. Glycolysis and Fermentation • All cells break down complex organic compounds into simpler molecules • As the compounds are broken down, cells release energy • Some of the energy is used to make ATP from ADP

  3. Harvesting Chemical Energy • ATP is the main energy currency of cells • Cellular respiration- the complex process in which cells make ATP by breaking down organic compounds

  4. Cellular Respiration • Begins with glycolysis • Glycolysis yields a small amount of ATP • Two possible pathways depending on the presence or absence of oxygen

  5. Aerobic vs. Anaerobic • Aerobic: oxygen is present (pathway will lead to aerobic respiration) • Anaerobic: oxygen is absent (pathway leads to fermentation)

  6. Glycolysis • Takes place in the cytosol of the cell • Involves four main steps • One 6-Carbon molecule of glucose is oxidized to produce two three-Carbon molecules of pyruvic acid

  7. Two ATP molecules are used in step 1 • Four ATP molecules are produced in step 4 • Glycolysis has a net yield of 2 ATP

  8. Fermentation • Occurs in the absence of oxygen • Converts pyruvic acid into other compounds • These pathways regenerate NAD+

  9. Lactic Acid Fermentation • An enzyme converts pyruvic acid into another 3-carbon compound called lactic acid • Two hydrogen atoms are transferred to pyruvic acid

  10. Uses of Lactic Acid • Microorganisms are used for lactic acid fermentation in cheese and yogurt • Also occurs in muscle cells during strenuous exercise (muscle cells use up oxygen faster than it can be delivered)

  11. Alcoholic Fermentation • Plant cells and unicellular organisms, such as yeast, convert pyruvic acid into ethyl alcohol • Used in bread, wine, beer, etc.

  12. Energy Yield • Energy is measured in units of kilocalories (kcal) • One kilocalorie equals 1000 calories (cal) • Oxidation of a standard amount of glucose releases 686 kcal

  13. Efficiency of Glycolysis • Efficiency of = energy required to make ATP glycolysis energy released by oxidation of glucose = 2 X 12 kcal X 100% 686 kcal = 3.5%

  14. Anaerobic pathways probably evolved very early in the history of life on Earth • For more than a billion years, this was the only pathway available for harvesting chemical energy • The first organisms to use anaerobic pathways were bacteria

  15. Larger organisms have greater energy requirements that cannot be met by only anaerobic pathways • Must use aerobic respiration

  16. Chapter 7 Section 7.2

  17. Aerobic Respiration • Produces 20 times as much ATP as produced by glycolysis alone • Has two major stages: the Krebs cycle and the electron transport chain

  18. Energy Yield • Maximum of 38 ATP molecules can be produced from 1 molecule of glucose • Efficiency = Energy required to make ATP Energy released by oxidation of glucose = 38 X 12 kcal X 100% = 66% 686 kcal

  19. Aerobic respiration is nearly 20 times more efficient than glycolysis alone • Glucose  glycolysis  pyruvic acid  acetyl CoA  Krebs cycle

  20. Summarizing Cellular Respiration • C6H12O6 + 6O2 6 CO2 + 6H2O + energy • Cellular respiration provides ATP that all cells need to support the activities of life

  21. Also provides carbon skeletons that can be built up into larger molecules • Cells need specific organic compounds to build macromolecules

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