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Cellular Metabolism

Cellular Metabolism. Biol 105 Lecture 6 Read Chapter 3 (pages 63 – 69). Metabolism. Consists of all of the chemical reactions that take place in a cell. Metabolism. Animation—Breaking Down Glucose For Energy http://wps.aw.com/bc_goodenough_boh_4/177/45509/11650544.cw/index.html.

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Cellular Metabolism

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  1. Cellular Metabolism Biol 105 Lecture 6 Read Chapter 3 (pages 63 – 69)

  2. Metabolism • Consists of all of the chemical reactions that take place in a cell

  3. Metabolism Animation—Breaking Down Glucose For Energy http://wps.aw.com/bc_goodenough_boh_4/177/45509/11650544.cw/index.html

  4. Cellular Metabolism • Aerobic cellular respiration – requires oxygen, produces carbon dioxide • Anaerobic Fermentation – does not require oxygen

  5. Summary of Cellular Respiration Electrons transferred by NADH Cytoplasm Blood vessel Electrons transferred by NADH Glucose Electrons transferred by NADH and FADH2 Plasma membrane Carrier protein Electron Transport Chain Citric Acid Cycle Transition Reaction Glycolysis glucose pyruvate Oxygen Mitochondrion  +2 ATP +2 ATP +32 ATP 36 ATP Extracellular fluid Figure 3.27

  6. Aerobic Cellular respiration • In aerobic cellular respiration cells take in sugar (glucose) and breaks it down to into carbon dioxide and water, this requires oxygen. • This process produces energy in the form of ATP • C6H12O6 + 6O2 → 6CO2 +6H2O + Energy

  7. Aerobic Cellular respiration • There are four steps of aerobic cellular respiration: • Glycolysis • Transition Reaction • Citric Acid Cycle (Krebs Cycle) • Electron Transport Chain

  8. NADH and FADH2 are important carriers of electrons

  9. Cellular Respiration - Glycolysis • Phase 1: Glycolysis • Occurs in the cytoplasm • Splits one glucose into two pyruvate molecules • Generates a net gain of 2 ATP and 2 NADH molecules • Does not require oxygen

  10. Cellular Respiration - Glycolysis • Starts with glucose • Ends with 2 ATP, 2 NADH, 2 pyruvate

  11. Glycolysis Glycolysis (in cytoplasm) Cytoplasm During the first steps, two molecules of ATP are consumed in preparing glucose for splitting. Glucose During the remaining steps, four molecules of ATP are produced. 2 ATP Energy- investment phase 2 ADP 4 ADP 4 ATP Energy- yielding phase The two molecules of pyruvate then diffuse from the cytoplasm into the inner compartment of the mitochondrion, where they pass through a few preparatory steps (the transition reaction) before entering the citric acid cycle. 2 NAD+ 2 NADH Two molecules of nicotine adenine dinucleotide (NADH), a carrier of high-energy electrons, also are produced. 2 Pyruvate Figure 3.23

  12. In Cytosol

  13. Cellular Respiration – Transition Reaction • Phase 2: Transition reaction • Occurs within the mitochondria • Coenzyme A combines with pyruvate and CO2 is removed from each pyruvate • Forms 2 acetyl CoA molecules • Produces 2 NADH

  14. Transition Reaction • Start with: • 2 pyruvate (3 carbon molecules) • 2 Coenzyme A • End with: • 2 CO2 • 2 NADH • 2 Acetyl CoA (2 carbon molecule)

  15. Transition Reaction Transition Reaction (in mitochondrion) Pyruvate (from glycolysis) One carbon (in the form of CO2) is removed from pyruvate. A molecule of NADH is formed when NAD+ gains two electrons and one proton. CO2 NAD+ Coenzyme A NADH (electron passes to electron transport chain) The two-carbon molecule, called an acetyl group, binds to coenzyme A (CoA), forming acetyl CoA, which enters the citric acid cycle. CoA Acetyl CoA Citric Acid Cycle Figure 3.24

  16. Cellular Respiration – Citric acid cycle • Phase 3: Citric acid cycle • Occurs in the mitochondria • Acetyl CoA enters the citric acid cycle • Releases 2 ATP, 2 FADH2 and 6 NADH, 4 CO2 molecules • Requires oxygen

  17. Citric Acid Cycle • Also called the Krebs Cycle • Start with 2 Acetyl CoA • End with: • 4 CO2 • 2 ATP • 6 NADH and 2 FADH2

  18. Citric Acid Cycle Citric Acid Cycle (in mitochondrion) Acetyl CoA, the two-carbon compound formed during the transition reaction, enters the citric acid cycle. The citric acid cycle also yields several molecules of FADH2 and NADH, carriers of high-energy electrons that enter the electron transport chain. Acetyl CoA CoA CoA Oxaloacetate Citrate NADH CO2 leaves cycle NAD+ NAD+ Citric Acid Cycle Malate NADH FADH2 Pi ADP + ATP FAD -Ketoglutarate Succinate CO2 leaves cycle NAD+ NADH The citric acid cycle yields One ATP from each acetyl CoA that enters the cycle, for a net gain of two ATP. Figure 3.25

  19. Cellular Respiration • Phase 4: Electron transport chain • Electrons of FADH2 and NADH are transferred from one protein to another, until they reach oxygen • Releases energy that results in 32 ATP • Requires oxygen

  20. The Big Pay Off – Electron Transport Chain • NADH and FADH2 are important carriers of electrons • They donate electrons to the electron transport chain • At the end of the chain oxygen accepts the electrons.

  21. The Big Pay Off – Electron Transport Chain • Electron Transport Chain produces ATP using the ATP synthase protein molecule • The Electron Transport Chain produces 32 ATP

  22. Electron Transport Chain Electron Transport Chain (inner membrane of mitochondrion) The molecules of NADH and FADH2 produced by earlier phases of cellular respiration pass their electrons to a series of protein molecules embedded in the inner membrane of the mitochondrion. High NADH NAD+ As the electrons are transferred from one protein to the next, energy is released and used to make ATP. 2e– FADH2 Membrane proteins 2e– FAD Potential energy Eventually, the electrons are passed to oxygen, which combines with two hydrogens to form water. 2e– 2e– 2e– H2O Low 1 + 2 H+ O2 2 Energy released is used for synthesis of ATP Figure 3.26

  23. How is ATP made using the ETC • In the mitochondria, the NADH and FADH donate electrons to the electron transport chain (ETC) • Oxygen is the final electron acceptor from the ETC • The ETC uses the energy from the electrons to transport H+ against the concentration gradient, transporting them from the lumen of the mitochondria to the intermembrane space.

  24. How is ATP made using the ETC • The ATPsynthase transports the H+ back to the lumen of the mitochondria. • The H+ falling through the ATPsynthase provides the energy for the ATPsynthase to catalyze the reaction of ADP + P →ATP

  25. Summary of Cellular Respiration Table 3.5

  26. Summary of Cellular Respiration • One molecule of glucose is broken down and 36 ATP are generated. • Oxygen is used by the electron transport chain – it accepts electrons from the ETC • Carbon dioxide is produced by the Transition Reaction and the Citric acid cycle

  27. Summary of Cellular Respiration • Glycolysis: Starts the process by taking in glucose. Produces 2 ATP • The Transition Reaction produces CO2 and NADH • The Citric acid cycle: Produces 2 ATP but also produces lots of NADH and FADH2. Produces CO2.

  28. Summary of Cellular Respiration • Electron transport chain • Takes electrons from NADH and FADH2 and uses them to produce ATP using the ATP synthase molecule. • Requires oxygen. Oxygen is the final electron acceptor on the electron transport chain • One glucose can produce a total of 36 ATP

  29. Complex Carbohydrates must first be broken down into glucose before entering glycolysis Fats and proteins enter the process at different steps

  30. Oxygen • Cellular respiration requires oxygen – this is aerobiccellular respiration • Sometimes organisms, including humans, need to produce energy without using oxygen • When you need energy quick, or if there is not enough O2 then the cell will use only glycolysis

  31. Anaerobic Fermentation • Breakdown of glucose without oxygen • Takes place entirely in the cytoplasm • It is very inefficient - results in only two ATP

  32. Anaerobic Fermentation • Anaerobic Fermentation: Anaerobic pathway to produce ATP from glycolysis without the Krebs and ETC

  33. Fermentation in Animals • When cells need energy quick they will use this pathway for a short time • 2 pyruvic acid + 2 NADH → 2 lactate and 2 NAD+ • End result = lactate and 2 ATP produced (from glycolysis) and NAD+ is regenerated

  34. What is the starting molecule of glycolysis? • Acetyl CoA • Protein • Glucose • Pyruvate (pyruvic acid)

  35. Which stage produces CO2 • Glycolysis • Electron Transport Chain • Transition • Citric acid Cycle • Both 3 and 4

  36. Which stage uses O2 • Glycolysis • Krebs Cycle • Electron Transport Chain

  37. Which stage produces the most NADHs • Glycolysis • Krebs Cycle • Electron Transport Chain

  38. Which stage produces the most ATP • Glycolysis • Krebs Cycle • Electron Transport Chain

  39. Important Concepts • Read Ch 4 • What is Cellular respiration and Anaerobic Fermentation and what are the differences between them. • What are the four steps of aerobic cellular respiration, what happens in each step, what are the starting molecules, what comes out of each step, where in the cell does each step occur, how many ATP and NADH/FADH2 are produced in each step.

  40. Important Concepts • Describe in detail how is ATP made using the electron transport chain • What is the role of ATPsynthase, H+, O2, NADH and FADH2 and the electron transport chain in ATP production? • Know the overall picture of cellular respiration (summary slides)

  41. Important Concepts • What is the role of oxygen in cellular respiration, what steps produce carbon dioxide • What is anaerobic fermentation, what steps are involved in fermentation, what end products are produced in humans, is oxygen required? when is it used.

  42. Definitions • Aerobic cellular respiration, anaerobic fermentation , ATP synthase, metabolism

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