Energy Releasing Pathways: Cellular Respiration and Glycolysis Biology 1010 -Chapter 8

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Energy Releasing Pathways: Cellular Respiration and Glycolysis Biology 1010 -Chapter 8 Slide 2 Introduction A. Unity of Life 1. all organisms use energy 2. byproducts of metabolism a. carbon dioxide b. water c. heat 3. at the biochemical level, all life is united Slide 3 Process of ATP Synthesis A. Comparison of Pathways 1. ATP is the energy currency of all cells 2. glycolysis a. common to all pathways b. splitting of glucose forms ATP c. occurs in the cytoplasm of the cell Slide 4 2. Fermentation and anaerobic electron transport a. occur in the absence of oxygen b. release small amounts of ATP 3. Aerobic respiration a. main pathway for converting CHO to ATP b. occurs in the mitochondria c. requires oxygen d. efficient Slide 5 4. chemical formula H 2 O +C 6 H 12 O 6 + O 2 = CO 2 + H 2 O 5. similarities to photosynthesis Slide 6 Slide 7 Glycolysis A. First stage of all energy-releasing pathways 1. occurs in the cytoplasm of the cell 2. does not require oxygen 3. evolutionary considerations Slide 8 B. Stages 1. energy investment phase a. glucose is phosphorylated by 2 ATP molecules 2. energy releasing phase a. glucose is split to form 4 ATP and 2 pyruvate molecules. b. electrons captured by NAD+ to form NADH (to ETS) c. ATP is produced by substrate- level phosphorylation. Slide 9 Slide 10 Slide 11 C. Inputs and Outputs 1. Inputs a. glucose b. NAD+ c. ADP 2. Outputs a. 2 pyruvate b. 2 NADH c. 2 ATP (net) Slide 12 Slide 13 Krebs Cycle: Aerobic Respiration A. General 1. occurs in the mitochondria (inner membrane space) 2. requires oxygen 3. input is the pyruvate (3-C)from glycolysis, which is modified to form acetyl-CoA 4. carbon leaves the cycle as CO 2 Slide 14 B. Stages 1. pyruvate is converted to acetyl-CoA 2. oxygen is used to break C-C bonds 3. broken bonds release energy and electrons. 4. energy is used to form ATP by oxidative phosphorylation 5. electrons captured by NAD+ and FAD+ to form NADH and FADH 2 (to ETS) Slide 15 6. carbon leaves as CO 2 7. cyclic pathway - intermediates are recycled 8. 1 glucose = 2 pyruvate. Two complete turns of the pathway per glucose molecule 9. 2 ATP produced per glucose Slide 16 C. Inputs and Outputs 1. Inputs a. pyruvate b. NAD+ and FAD+ c. ADP d. O 2 2. Outputs (per glucose) a. CO2 b. NADH and FADH 2 c. 2 ATP Slide 17 Slide 18 Slide 19 Electron Transport System (ETS) A. General 1. inputs are the NADH and FADH 2 from glycolysis and the Krebs cycle a. processes electrons, not carbon 2. located on the inner membrane of the mitochondria (integral proteins) 3. uses oxygen as a terminal electron receptor Slide 20 4. ATP is produced by chemiosmosis or electron-level phosphorylation B. Stages of chemiosmosis 1. NADH and FADH 2 transfer electrons to integral proteins on the inner membrane a. electrons are high energy 2. passage of energy between proteins pumps H+ ions out of the inner space a. generates an electrical gradient Slide 21 3. channels are opened, allowing the H+ ions to reenter, generating ATP. 4. oxygen is used to gather the spent electrons, generating water 5. high amounts of ATP are produced, typically 32 ATP per glucose. 6. NAD+ and FAD+ are recycled Slide 22 C. Inputs and Outputs 1. Inputs a NADH and FADH 2 b. ADP c. O 2 2. Outputs (per glucose) a. H 2 O b. NAD+ and FAD+ c. 32 ATP Slide 23 Slide 24 Slide 25 Summary of Energy Harvest A. ATP per glucose 1. glycolysis 2 ATP 2. Krebs 2 ATP 3. ETS 32 ATP B. Variations 1. yield per glucose may be 32-38 ATP depending on cell type Slide 26 Slide 27 Anaerobic Respiration A. General 1. occur in the absence of oxygen or oxygen-poor environments 2. after glycolysis, pyruvate is converted to other molecules than acetyl-CoA. 3. many bacteria are completely anaerobic Slide 28 B. Fermentation Pathways 1. Lactate fermentation a. pyruvate is converted to lactate b. process regenerates NAD+ c. occurs in bacteria and muscle cells 2. Alcohol fermentation a. pyruvate is converted to acetaldehyde and then alcohol b. NAD+ is regenerated Slide 29 Slide 30 C. Anaerobic electron transport 1. some bacteria have modified electron transport systems. 2. types a. convert SO 4 to H 2 S b. convert NO 3 to NO 2 3. evolutionary significance