Chapter 9. Cellular Respiration: Harvesting Chemical Energy. m/watch?v=9wjdfc 5ISKw

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1 Chapter 9 Cellular Respiration: Harvesting Chemical Energy m/watch?v=9wjdfc 5ISKw

2 Principles of Energy Harvest Photosynthesis vs. Cellular respiration

3 Principles of Energy Harvest Photosynthesis Cellular respiration Endergonic Exergonic Products: O 2, Products: CO 2, C 6 H 12 O 6 H 2 O, ENERGY Reactants: CO 2, Reactants: O 2, H 2 O, ENERGY C 6 H 12 O 6 Chloroplasts Mitochondria

4 Principles of Energy Harvest Cell respiration is catabolic Breaks down glucose Photosynthesis is anabolic Synthesizes glucose

5 Redox reactions Oxidation - Reduction Oxidation is e- or H loss Reduction is e- or H gain Reducing agent: e- donor Oxidizing agent: e- acceptor

6 Oxidizing agent in respiration NAD+ (nicotinamide adenine dinucleotide) Removes electrons from food (series of reactions) NAD+ is reduced to NADH Enzyme action: dehydrogenase Oxygen is the eventual e- acceptor

7 Electron transport chains Electron carrier molecules (membrane proteins) Shuttles electrons that release energy used to make ATP Sequence of reactions that prevents energy release in 1 explosive step Electron route: food---> NADH ---> electron transport chain ---> oxygen

8 Cellular respiration summary Glycolysis: cytosol; degrades glucose into pyruvate Kreb s Cycle: mitochondrial matrix; pyruvate into carbon dioxide Electron Transport Chain: inner membrane of mitochondrion; electrons passed to oxygen

9 Glycolysis 1 Glucose ---> 2 pyruvate molecules The First Stage of Respiration for ALL living organisms, anaerobes or aerobes, is called Glycolysis and takes place in the Cytosol.

10 2 Pyruvic Acid Net Result 2 ATP per glucose (4 2 = 2) 2 NADH In summary, glycolysis takes one glucose and turns it into 2 pyruvates (molecules of pyruvic acid), 2 NADH and a net of 2 ATP.

11 Glycolysis Glucose 4 ATP s are produced (6 carbons) 2 ATP s supply the activation energy Pyruvic Acid (3 Carbons) Pyruvic Acid (3 Carbons) 2 NAD e- 2 NADH 4 ATP Yield = 2 ATP Net Gain

12 Glycolysis 1 Glucose ---> 2 pyruvate molecules Energy investment phase: cell uses ATP to phosphorylate fuel Energy payoff phase: ATP is produced by substrate-level phosphorylation and NAD+ is reduced to NADH by food oxidation Net energy yield per glucose molecule: 2 ATP plus 2 NADH; no CO 2 is released; occurs aerobically or anaerobically (no O 2 used)

13 In order for Aerobic Respiration to continue the Pyruvic acid is first converted to Acetic Acid by losing a carbon atom and 2 oxygens as CO 2. The Acetic acid then must enter the matrix region of the mitochondria. The CO 2 produced is the CO 2 animals exhale when they breathe. Mitochondrion

14 The Krebs Cycle (AKA the Citric Acid Cycle, Tricarboxylic Acid Cycle) Sir Hans Adolf Krebs Produces most of the cell's energy in the form of NADH and FADH 2 not ATP Does NOT require O 2

15 Each pyruvate is converted into acetyl CoA (x 2): CO2 is released NAD+ ---> NADH coenzyme A (from B vitamin), makes molecule very reactive From this point, each turn 2 C atoms enter (pyruvate) and 2 exit (carbon dioxide) Kreb s Cycle Creates NADH + FADH 2 + ATP

16 The cycle : Oxaloacetate is regenerated Kreb s Cycle Requires O 2, creates NADH + FADH 2 + ATP For each pyruvate that enters (x2): 3 NAD+ reduced to NADH 1 FAD+ reduced to FADH2 (riboflavin, B vitamin) 1 ATP molecule

17 Krebs cycle Summary Occurs in matrix of mitochondrion As a result of one turn of the Krebs cycle the cell makes: 1 FADH 2 3 NADH 1 ATP However, each glucose produces two pyruvic acid molecules. So the total outcome is: 2 FADH 2 6 NADH 2 ATP

18 Oxidative Phosphorylation Occurs in inner mitochondrial membrane Only phase that requires O 2 Requires NADH or FADH 2 ADP and P O 2

19 Electron transport chain

20 The Chemiosmotic Hypothesis proposes that the Electron Transport Chain energy is used to move H + (protons) across the cristae membrane, and that ATP is generated as the H + diffuse back into the matrix through ATP Synthase.

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22 Electron transport chain Cytochromes carry electron carrier molecules (NADH & FADH 2 ) down to oxygen Chemiosmosis: energy coupling mechanism ATP synthase (enzyme): produces ATP using H+ gradient (proton-motive force) pumped into the inner membrane space from the electron transport chain harnesses the flow of H+ back into the matrix to phosphorylate ADP to ATP (oxidative phosphorylation)

23 Review: Cellular Respiration 38 molecules ATP/glucose molecule (theoretically!) 1. Glycolysis: 2 ATP (substrate-level phosphorylation) 2. Kreb s Cycle: 2 ATP (substrate-level phosphorylation) 3. Electron transport & oxidative phosphorylation: 2 NADH (glycolysis) = 6ATP 4. 2 NADH (acetyl CoA) = 6ATP 6 NADH (Kreb s) = 18 ATP 2 FADH2 (Kreb s) = 4 ATP 38 TOTAL ATP/glucose

24 How other nutrients enter the catabolic pathway

25 Control of Glucose Catabolism

26 But Theoretical ATP Yield of Aerobic Respiration Usually Said to be 36 ATP

27 Why can t we agree?

28 Related metabolic processes Fermentation: 1. Alcohol: pyruvate to ethanol 2. Lactic acid: pyruvate to lactate Facultative anaerobes (yeast/bacteria) Beta-oxidation lipid catabolism

29 Two Types of Cellular Respiration There are two types of Respiration: Anaerobic Respiration and Aerobic Respiration Some organisms use the Anaerobic Respiration pathway, and some organisms use the Aerobic Respiration pathway.

30 Anaerobic Respiration: Alcoholic Fermentation is carried out by yeast, a kind of fungus.

31 Alcoholic Fermentation (Ethyl Alcohol or Ethanol) C 6 H 12 O 6 2 C 2 H 5 OH + 2 CO 2 As a result of Alcoholic Fermentation, Glucose is converted into 2 molecules of Ethyl Alcohol and 2 Molecules of Carbon Dioxide.

32 Alcoholic Fermentation Glucose (6 carbons) Glycolysis 4 ATP s are produced 2 ATP s supply the activation energy Pyruvic Acid (3C) Pyruvic Acid (3C) Released into the environment CO 2 (C 2 H 5 OH) Ethyl Alcohol (2C) Released into the environment CO 2 Ethyl Alcohol (2C) (C 2 H 5 OH) 2 NAD e- 2 NADH 2 NAD e- 4 ATP Yield = 2 ATP Net Gain

33 Anaerobic Respiration: Lactic Acid Fermentation Occurs in animals Uses only Glycolysis. Does NOT require O 2 Produces ATP when O 2 is not available. Carried out by human muscle cells under oxygen debt. Lactic Acid is a toxin and causes fatigue, soreness and stiffness in muscles. Diffuses into blood, detoxified by liver.

34 Lactic Acid Fermentation Glycolysis 4 ATP s are produced Pyruvic Acid (3C) Lactic Acid (3C) Glucose (6 carbons) 2 ATP s supply the activation energy Pyruvic Acid (3C) Lactic Acid (3C) 2 NAD e- 2 NADH 2 NAD e- 4 ATP Yield = 2 ATP Net Gain

35 Lab 5 rz43rk