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General Biology I Lab

General Biology I Lab. Lab #5: Cellular Respiration and Fermentation Instructor: Kristine A. Cooper. Purpose. To understand energy transformations in cells.

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General Biology I Lab

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  1. General Biology I Lab Lab #5:Cellular Respiration and Fermentation Instructor:Kristine A. Cooper

  2. Purpose • To understand energy transformations in cells. • We will investigate the processes of fermentation and cellular respiration, which transfer energy in glucose bonds to ATP (chemical energy). • This ATP is then used to power the cell.

  3. Redox Reactions • Fermentation and cellular respiration both involve oxidation-reduction (redox) reactions. • Oxidation=loss of electron(s) • Reduction=gain of electron(s) • LEO the lion says GER

  4. Cellular respiration • Consists of 3 stages • Glycolysis • Occurs in cytoplasm • Krebs Cycle or Citric Acid Cycle • Occurs in mitochondria • Electron Transport Chain (ETC) • Occurs in mitochondria

  5. 3 stages of respiration

  6. Redox Reactions of Respiration • Glucose is oxidized (loss of 2 hydrogen atoms) • NAD+- coenzyme which is reduced (receives 2 electrons) from glucose to become NADH

  7. First stage:Glycolysis Consists of a series of steps that oxidize glucose to pyruvate. 2 ATP produced

  8. Second stage:Kreb’s Cycle • Prior to the Kreb’s Cycle pyruvate is converted to Acetyl CoA • During the Kreb’s Cycle many NADH and FADH2 are generated (electron carriers) • 2 ATP are produced

  9. Third stage:Electron Transport Chain and Chemiosmosis • ETC- electrons from NADH and FADH2 power H+ pump across mitochondrial membrane • Oxygen is needed as a final electron acceptor • H+ gradient is stored energy, which diffuses back through membrane causing formation of ATP • Max ATP production of 34 ATP

  10. A total of 38 ATP are produced.

  11. Fermentation • Occurs during anaerobic conditions • Oxygen cannot be the final electron acceptor in ETC and therefore Kreb’s cycle and ETC are inhibited • Single stage - only glycolysis occurs • There are 2 forms of fermentation: • Alcoholic fermentation- occurs in plants, some fungi, and yeast • Lactic Acid Fermentation- occurs in animals, certain fungi, and some bacteria

  12. Alcoholic Fermenation • Alcoholic fermentation- convert pyruvate from glycolysis to ethanol and carbon dioxide

  13. Lactic Acid Fermenation • Lactic acid fermentation- converts pyruvate from glycolysis to lactate.

  14. Why Ferment? If cellular respiration can create 38 ATP from a single glucose, why would an organism want to ferment glucose to only 2 ATP?

  15. Today’s Lab: Alcoholic Fermentation • CO2 is a product of alcoholic fermentation • We will measure rate of fermentation in yeast by monitoring amount of CO2 produced using a respirometer.

  16. succinate fumarate H+ + e- DPIP-oxidized (blue) DPIP-reduced (colorless) Today’s Lab: Cellular Respiration • Monitoring the conversion on succinate to fumarate during the Kreb’s cycle to determine rate of respiration • DPIP is reduced during this reaction turning it from blue to colorless • The degree of color change will be measured by the amount of light it absorbs in a spectrophotometer

  17. Today’s Mission • Complete 5.1A, 5.2A • Complete and fill in lab worksheet. • QUIZ #2 OPENS TODAY • The lab practical is in three weeks. Be sure to begin studying now!

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