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Cellular Respiration

Cellular Respiration. Chapter 9. Finding Energy. All energy ultimately comes from the sun Energy flows into an ecosystem as sunlight and leaves as heat Chemical components are recycled. Redox Reactions. Energy is released from the transfer of e - ’s

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Cellular Respiration

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  1. Cellular Respiration Chapter 9

  2. Finding Energy • All energy ultimately comes from the sun • Energy flows into an ecosystem as sunlight and leaves as heat • Chemical components are recycled

  3. Redox Reactions • Energy is released from the transfer of e-’s • Oxidation is a loss of (hydrogen) e-’s • Reduction is a gain of (hydrogen) e-’s • Reduce (+) charge of an atom by adding a (-) charge e- • LEO goes GER or OIL RIG • Always occur together

  4. Organic Molecules as Fuel • Organic molecules have high abundance of hydrogen • Energy released as O2 oxidizes (accepts e-’s from) H2 • e-’s travel with a proton (hydrogen atom) • PE lost as e-’s ‘fall’ down an energy gradient (move towards more EN molecule) • Lower energy state from less complex molecules • Enzymes needed to facilitate in animals because of energy of activation (EA)

  5. Electron Transport Train • Glucose (C6H12O6) is oxidized during cellular respiration • Occurs in steps to effectively access and use energy (avoids explosions) • e-’s transferred to an electron carrier, not directly to O2 • Coenzyme NAD+as an oxidizing agent (e- acceptor) • Dehydrogenase removes a pair of hydrogen atoms (2 e-’s and 2 protons)

  6. Controlling Energy Release • With no intermediates reaction = explosion • Little PE lost with e- transfer to NAD+ • Each NADH stores energy for ‘fall’ to O2 (final e- acceptor) • Electron transport chain, proteins within inner mitochondrial membrane,controls • Each carrier more EN than previous

  7. Cellular Respiration • 3 metabolic stages • Glycolysis: in cytosol, breaks down glucose into pyruvate • Citric acid cycle: in mitochondrial matrix, oxidizes pyruvate to create CO2 • Oxidative phosphorylation: mitochondrial matrix, e-’s to O2 and H+ = H2O and synthesizes ATP • Makes 36-38 ATP • Glucoses stores 686 kcal/mol of energy in bonds • ATP has 7.3 kcal/mol • Single, large unit of energy broken into smaller, more usable forms

  8. Glycolysis • Glucose (6C) 2 pyruvate (3C) • No CO2 released • Substrate-level phosphorylation • Can occur with or without O2 • O2 needed for citric acid cycle • No O2 then fermentation

  9. Transition Step • Pyruvate (3C) acetyl-CoA (2C) • High energy product so reacts exergonically • Decarboxylation is loss of CO2 • ‘Grooming’ for citric acid cycle

  10. Citric Acid Cycle (2 C’s) • Within mitochondria • Intermediate steps • Acetyl-CoA becomes citrate • CO2 and NADH leave as number of carbons reduces to 4 • FADH2 and an additional NADH leave • Oxaloacetate joins 2nd acetyl-CoA to reform citrate • Cycle repeats • 2 turns per 1 glucose Acetyl-CoA ATP + 3 NADH + FADH2 + CO2 Citrate (6 C’s) Oxaloacetate (4C’s) (4 C) molecule

  11. Oxidative Phosphorylation • 2 processes = ETC and chemiosmosis within inner mitochondrial membrane • NADH and FADH2 store most energy till now • Hydrogen concentration gradient setup • Components are protein pumps

  12. Electron Transport Chain • NADH and FADH2 bring e-’s to ETC complex • Oxidized when they lose e- to a lower neighbor (higher EN) • No direct ATP, control of energy release from fuel to oxygen (final acceptor) • Smaller, more manageable energy sources • FADH2 adds to lower energy level • Produce third less energy for ATP synthesis • Sets up a H+ concentration gradient

  13. Chemiosmosis • Energy stored as H+ gradient across a membrane drives cellular work • H+ ions pumped out by ETC • Sets up the gradient to drives ATP synthesis • ATP synthase is a protein complex that makes ATP from ADP and Pi • Endergonic reaction of ATP synthesis is coupled with exergonic ETC

  14. Cellular REspiration C6H12O6 + 6O2 6H2O + 6CO2 + 36-38 ATP + heat 1 NADH = 3 ATP 1 FADH2 = 2 ATP

  15. Oxidizing Fuel without Oxygen • Anaerobic respiration • ETC, but O2 not final e- acceptor • Fermentation • Primary purpose is to recycle NADH to NAD+ not ATP production • Pyruvate picks up e-’s (reduced) • Glycolysis • Occurs because NAD+ is oxidizer, not O2 • NAD+ recycling • NADH transfers e-’s to pyruvate to recycle NAD+

  16. Fermentation • Alcohol fermentation • Pyruvate to ethanol • Lose CO2 then reduced by NADH • In bacteria and yeast; makes bread, beer, and wine • Lactic acid fermentation • Pyruvate directly by NADH to lactate • No CO2 released • To make cheese and yogurt

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