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Cellular Respiration: Glycolysis, Respiration, and ATP Production

Learn about the processes of glycolysis, respiration, chemiosmosis, and ATP production in cellular respiration. Understand the roles of FADH2, NADH, and phosphorylation, as well as the importance of the citric acid cycle and the electron transport chain. Explore the recycling of NAD+ in fermentation and the breakdown of macromolecules for ATP production. Discover the chemical equation for cellular respiration and the energy flow in open systems.

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Cellular Respiration: Glycolysis, Respiration, and ATP Production

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  1. Chapter 9 Warm-Up Define: • Glycolysis • Respiration • Chemiosmosis • Phosphorylation • Fermentation • ATP (draw and label) • Electrochemical gradient • FAD  FADH2 • NAD+ NADH • What is the role of phosphofructokinase? How does it “work”? • Explain “glycolysis”. Where does it occur? How does it “work”?

  2. Chapter 9 Warm-Up • What is the chemical equation for cellular respiration? • Remember: OILRIG • In the conversion of glucose and oxygen to CO2 and H2O, which molecule is reduced? • Which is oxidized? • What happens to the energy that is released in this redox reaction? • NAD+ is called a(n) ________________. Its reduced form is _______.

  3. Chapter 9 Warm-Up • Which has more energy available: • ADP or ATP? • NAD+ or NADH? • FAD+ or FADH2? • Where does the Citric Acid Cycle occur in the cell? • What are the main products of the CAC?

  4. Chapter 9 Warm-Up • How is the proton gradient generated? • What is its purpose? • Describe how ATP synthase works.

  5. Chapter 9 Warm-Up • Where are the proteins of the ETC located? • Where does the ETC pump H+ ions into? • In cellular respiration, how many ATP are generated through: • Substrate-level phosphorylation? • Oxidative phosphorylation?

  6. Chapter 9 Warm-Up • In fermentation, how is NAD+ recycled? • You eat a steak and salad. Which macromolecule cannot be broken down to make ATP? • Think about the structure of a fat molecule. What feature of its structure makes it a better fuel than a carbohydrate (like glucose)? • Explain where the fat goes when you lose weight.

  7. Chapter 9 Warm-Up • In fermentation, how is NAD+ recycled? • What is the function of the enzyme phosphofructokinase? • You eat a steak and salad. Which macromolecule cannot be broken down to make ATP? • Explain where the fat goes when you lose weight.

  8. Chapter 9: Respiration

  9. What you need to know: • The summary equation of cellular respiration. • The difference between fermentation and cellular respiration. • The role of glycolysis in oxidizing glucose to two molecules of pyruvate. • The process that brings pyruvate from the cytosol into the mitochondria and introduces it into the citric acid cycle. • How the process of chemiosmosis utilizes the electrons from NADH and FADH2 to produce ATP.

  10. In open systems, cells require E to perform work (chemical, transport, mechanical) E flows into ecosystem as Sunlight Autotrophs transform it into chemical E O2 released as byproduct Cells use some of chemical E in organic molecules to make ATP E leaves as heat

  11. Catabolic Pathway Simpler waste products with less E Complex organic molecules Some E used to do work and dissipated as heat

  12. Respiration: exergonic (releases E) C6H12O6 + 6O2 6H2O + 6CO2 + ATP(+ heat) Photosynthesis: endergonic (requires E) 6H2O + 6CO2 + Light  C6H12O6 + 6O2

  13. Redox Reactions (oxidation-reduction) oxidation (donor) lose e- Xe- + Y  X + Ye- • Oxidation = lose e- • Reduction = gain e- C6H12O6 + 6O2 6H2O + 6CO2 + OiLRiG or LeoGer oxidation ATP reduction (acceptor) gain e- reduction

  14. Energy Harvest • Energy is released as electrons “fall” from organic molecules to O2 • Broken down into steps: Food (Glucose)  NADH  ETC  O2 • Coenzyme NAD+ = electron acceptor • NAD+ picks up 2e- and 2H+ NADH (stores E) • NADH carries electrons to the electron transport chain (ETC) • ETC: transfers e- to O2 to make H2O ; releases energy

  15. NAD+ as an electron shuttle

  16. Electron Transport Chain

  17. Stages of Cellular Respiration • Glycolysis • Pyruvate Oxidation + Citric Acid Cycle (Krebs Cycle) • Oxidative Phosphorylation (electron transport chain (ETC) & chemiosmosis)

  18. Overview of Cellular Respiration

  19. Cellular Respiration Stage 1: Glycolysis

  20. Glycolysis • “sugar splitting” • Believed to be ancient (early prokaryotes - no O2 available) • Occurs in cytosol • Partially oxidizes glucose (6C) to 2 pyruvates (3C) • Net gain: 2 ATP +2NADH • Also makes 2H2O • No O2 required

  21. Glycolysis Stage 1: Energy Investment Stage • Cell uses ATP to phosphorylate compounds of glucose Stage 2: Energy Payoff Stage • Two 3-C compounds oxidized • For each glucose molecule: • 2 Net ATP produced by substrate-level phosphorylation • 2 molecules of NAD+ NADH

  22. Substrate-Level Phosphorylation • Generate small amount of ATP • Phosphorylation: enzyme transfers a phosphate to other compounds • ADP + Pi ATP P compound

  23. Glycolysis (Summary) glucose 2 NAD+ 2 NADH + 2H+ 2 ATP 2H2O ADP P 2 pyruvate (3-C) C3H6O3

  24. Cellular Respiration Stage 2: Pyruvate Oxidation + Citric Acid Cycle

  25. Mitochondrion Structure Citric Acid Cycle (matrix) ETC (inner membrane)

  26. Pyruvate Oxidation • Pyruvate Acetyl CoA (used to make citrate) • CO2 and NADH produced

  27. Citric Acid Cycle (Krebs) • Occurs in mitochondrial matrix • Acetyl CoA Citrate  released • Net gain: 2 ATP,6 NADH, 2 FADH2(electron carrier) • ATP produced by substrate-level phosphorylation CO2

  28. Summary of Citric Acid Cycle

  29. http://multimedia.mcb.harvard.edu/anim_mitochondria.html BioVisions at Harvard:The Mitochondria

  30. Cellular Respiration Stage 3: Oxidative Phosphorylation

  31. Oxidative Phosphorylation Electron Transport Chain Chemiosmosis H+ ions pumped across inner mitochondrial membrane H+ diffuse through ATP synthase (ADP  ATP) • Occurs in inner membrane of mitochondria • Produces 26-28 ATP by oxidative phosphorylation via chemiosmosis

  32. Electron Transport Chain (ETC) • Collection of molecules embedded in inner membrane of mitochondria • Tightly bound protein + non-protein components • Alternate between reduced/oxidized states as accept/donate e- • Does not make ATP directly • Ease fall of e- from food to O2 • 2H+ + ½ O2 H2O

  33. As electrons move through the ETC, proton pumps move H+ across inner mitochondrial membrane

  34. Chemiosmosis: Energy-Coupling Mechanism • Chemiosmosis = H+ gradient across membrane drives cellular work • Proton-motive force: use proton (H+) gradient to perform work • ATP synthase: enzyme that makes ATP • Use E from proton (H+) gradient – flow of H+ back across membrane

  35. Chemiosmosis couples the ETC to ATP synthesis

  36. oxidative phosphorylation uses which couples chemiosmosis generates proton gradient ATP uses E to produce called redox reactions H+ pumped from matrix to intermembrane space proton motive force of ETC drives in which H+ e- passed down E levels through ATP synthase to final e- acceptor O2 H2O

  37. ATP yield per molecule of glucose at each stage of cellular respiration

  38. BioFlix: Cellular Respiration

  39. Anaerobic Respiration: generate ATP using other electron acceptors besides O2 • Final e- acceptors: sulfate (SO4), nitrate, sulfur (produces H2S) • Eg. Obligate anaerobes: can’t survive in O2 • Facultative anaerobes: make ATP by aerobic respiration (with O2 present) or switch to fermentation (no O2 available) • Eg. human muscle cells

  40. Fermentation = glycolysis + regeneration of NAD+

  41. Glycolysis Without O2 O2 present Fermentation Respiration Release E from breakdown of food with O2 Occurs in mitochondria O2 required(final electron acceptor) Produces CO2, H2O and up to 32 ATP • Keep glycolysis going by regenerating NAD+ • Occurs in cytosol • No oxygenneeded • Creates ethanol [+ CO2]or lactate • 2 ATP (from glycolysis)

  42. Types of Fermentation Alcohol fermentation Lactic acid fermentation Pyruvate  Lactate Ex. fungi, bacteria, human muscle cells Used to make cheese, yogurt, acetone, methanol Note: Lactate build-up causes muscle fatigue and pain • Pyruvate  Ethanol + CO2 • Ex. bacteria, yeast • Used in brewing, winemaking, baking

  43. Various sources of fuel • Carbohydrates, fats and proteins can ALL be used as fuel for cellular respiration • Monomers enter glycolysis or citric acid cycle at different points

  44. Phosphofructokinase: • Allosteric enzyme that controls rate of glycolysis and citric acid cycle • Inhibited by ATP, citrate • Stimulated by AMP • AMP+ P + P ATP

  45. Respiration: Big Picture

  46. ENERGY aerobic cellular respiration (with O2) anaerobic (without O2) glycolysis (cytosol) mitochondria Fermentation (cytosol) pyruvate oxidation ethanol + CO2 (yeast, some bacteria) substrate-level phosphorylation citric acid cycle lactic acid (animals) ETC oxidative phosphorylation chemiosmosis

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