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Cellular Respiration

Cellular Respiration. Cellular respiration – process in which mitochondria break down food molecules to produce ATP in plants & animals; occurs in the presence of oxygen Nutrients + oxygen water+ ATP+ CO 2 The equation for cellular respiration is:

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Cellular Respiration

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  1. Cellular Respiration

  2. Cellular respiration – process in which mitochondria break down food molecules to produce ATP in plants & animals; occurs in the presence of oxygen Nutrients + oxygen water+ ATP+ CO2 The equation for cellular respiration is: 6O2 + C6H12O6 → 6CO2 + 6H2O + Energy oxygen + glucose → carbon dioxide + water + energy • Process changes organic chemical energy (glucose) into inorganic chemical energy ATP

  3. Overview of Cellular Respiration 3 Stages: • Glycolysis – anaerobic process; does not require oxygen - cytoplasm • Citric Acid (Krebs) Cycle – aerobic; does require oxygen – mitochondria • Electron Transport Chain – aerobic; does require oxygen - mitochondria

  4. Glycolysis • Glycolysis – breaks down glucose into two molecules of pyruvic acid (colorless acid) • This reaction uses enzymes and takes place in the cytoplasm of the cell (anaerobic reaction) Produces: • 2 Pyruvic acid molecules (used in Step 2 of cellular respiration) • 2 ATP molecules (energy cell can use) • 2 NADH molecules (electron carrier)

  5. At the beginning of glycolysis, the cell uses up 2 molecules of ATP to start the reaction. 4 ADP 2 ATP 4 ATP 2 ADP 2 ATP 2NAD+ 2 Pyruvic acid 2 To the electrontransport chain

  6. Fermentation • Fermentation releases energy from food molecules by producing ATP in the absence of oxygen; anaerobic process • During fermentation, cells convert NADH to NAD+ by passing high-energy electrons back to pyruvic acid. • This action converts NADH back into NAD+, and allows glycolysis to continue producing a steady supply of ATP.

  7. 2 Types of Fermentation 1. Lactic acid fermentation – process that supplies energy when O2 is scarce Ex.) released during vigorous exercise; “feel the burn” 2.Alcoholic fermentation – used to produce CO2 and ethyl alcohol Ex.) Yeast Cells

  8. The Krebs Cycle • Named after Hans Krebs – British biochemist; won Nobel Prize in 1953 for discovery of this cycle • Aerobic process • Pyruvic acid produced from glycolysis along w/O2 start the 2nd stage of cellular respiration • Pyruvic acid is broken down into CO2 in a series of endergonic reactions

  9. 2 Parts of the Krebs Cycle Part A Step 1: Cycle begins when pyruvic acid enters the mitochondrion

  10. The Krebs Cycle 2. Carbon molecule is removed, forming CO2, & electrons are removed, changing NAD+ to NADH. 3. Coenzyme A joins the 2-carbon molecule, forming acetyl-CoA.

  11. The Krebs Cycle 4. Acetyl-CoA then adds the 2-carbon acetyl group to a 4-carbon compound, forming citric acid. Citric acid

  12. The Krebs Cycle Part B Step 1: Citric acid is broken down into a 5-carbon compound, then into a 4-carbon compound.

  13. The Krebs Cycle Step 2: Two more molecules of CO2 are released and electrons join NAD+ and FAD, forming NADH and FADH2.

  14. The Krebs Cycle Result: 1 molecule of ATP is produced

  15. Energy totals from 1 molecule of pyruvic acid is : • 4 NADH • 1 FADH2 • 1 ATP Electron Transport Chain = 3rd step in cellular respiration, aerobic process, uses the high-energy electron carriers from the Krebs Cycle to convert ADP into ATP. Carrier molecules produced are used to generate ATP via the Electron Transport Chain

  16. Electron Transport Chain • High-energy electrons from NADH and FADH2 are passed along the electron transport chain from one carrier protein to the next.

  17. The Totals • Glycolysis produces just 2 ATP molecules per molecule of glucose. • The complete breakdown of glucose through cellular respiration, including glycolysis, results in the production of 36 molecules of ATP.

  18. The Totals: Overview

  19. Comparing Photosynthesis and Cellular Respiration • Comparing Photosynthesis and Cellular Respiration • The energy flows in photosynthesis and cellular respiration take place in opposite directions.

  20. On a global level, photosynthesis and cellular respiration are also opposites. • Photosynthesis removes carbon dioxide from the atmosphere and cellular respiration puts it back. • Photosynthesis releases oxygen into the atmosphere and cellular respiration uses that oxygen to release energy from food.

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