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BI 211 Principles of Biology Fall 2009
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Lecture 2 Outline (Ch. 7) I. Overview of Cellular Respiration
Redox Reactions Steps of Respiration IV. Cellular Respiration A. Glycolysis B. Coenzyme Junction C. Citric Acid Cycle (aka Krebs/TCA cycle) D. Electron Transport Chain (ETC) E. Chemiosmosis Anaerobic respiration Respiration using other biomolecules
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Cellular Respiration Overall purpose: • convert fuels to energy
• animals AND plants • complementary to photosynthesis
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Cellular Respiration Cellular Respiration: (Exergonic)
• catabolizes sugars to CO2 • requires O2 • at mitochondrion
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Redox Reactions • as part of chemical reaction, e- are transferred
• e- transfer = basis of REDOX reactions (reduction) (oxidation)
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Redox Reactions • follow the H, e- w/them
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Redox Reactions Equation for respiration
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Redox Reactions • transfer of e- to oxygen is stepwise
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Redox Reactions • e- moved by NAD+ (niacin)
• when “carrying” e- (& H+), NADH • gained e- (& H+), reduced Where do e- come from? • food (glucose) Where do e- go? • glucose NADH ETC O2 (H2O)
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Steps of Respiration • Steps of respiration: 1. glycolysis
Coenzyme Junction 2. Citric acid cycle 3. ETC 4. Chemiosmosis
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Cellular Respiration • Stages of respiration:
1. Glycolysis – prep carbons
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Cellular Respiration 1. Glycolysis • 1 glucose (6C) 2 pyruvate (3C)
• key points: - inputs - ATP - NAD+/NADH - CO2 and H2O - outputs • eukaryotes AND prokaryotes
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Cellular Respiration Glycolysis -inputs: -outputs: Where do they go?
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Cellular Respiration Coenzyme Junction
• 2 pyruvate (3C) Acetyl CoA (2C) • pyruvate joins coenzyme A (vitamin B) • 2 C lost (as CO2) • 2 NAD+ NADH
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Steps of Respiration • Stages of respiration:
2. Citric acid cycle e- transfer: redox
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Cellular Respiration 2. Citric acid cycle • few ATP so far
• mitochondrial matrix • 2 Acetyl CoA (2C) join oxaloacetate (4C) • 2 citrate (6C) converted several steps, 4C lost (CO2) • e- to carriers (NAD+, FAD)
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Citric acid cycle -inputs: -outputs: Where do they go?
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Self-Check Step of Respiration Inputs Outputs CO2/H2O ATP produced
e- carriers loaded Glycolysis 1 glucose 2 pyruvate 2H2O 2 net 2 NADH Coenzyme Junction Citric Acid Cycle Electron Transport Chain Oxidative phosphorylation Fermentation
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Steps of Respiration • Steps of respiration: 1. glycolysis - cytosol
Coenzyme Junction 2. Citric acid cycle - mitochondrial matrix 3. ETC - inner mitochondrial membrane 4. Chemiosmosis - inner membrane to intermembrane space
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Steps of Respiration • Stages of respiration: ETC Proton Motive Force
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Substrate-level phosphorylation
Phosphate group moved from substrate to ADP yields ATP
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Cellular Respiration 3. Electron transport chain (ETC)
• lots of energy harvested • released in stages • so far, 4 ATP – substrate P • many ATP – oxidative phosphorylation
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Cellular Respiration – mitochondria revisited
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Cellular Respiration Electron transport chain (ETC)
• ETC e- collection molecules • embedded on inner mitochondrial membrane • accept e- in turn • e- ultimately accepted by O2 (O2 reduced to H2O)
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Electron transport chain (ETC)
-inputs: per glucose, -outputs: Where do they go? H+ NAD+/FAD
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Steps of Respiration • Stages of respiration: 4. Chemiosmosis
ATP produced!
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Cellular Respiration 4. Chemiosmosis
• ATP synthase: inner mitochondrial membrane • energy input ATP – H+ gradient • chemiosmosis – ion gradient to do work
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Cellular Respiration 4. Chemiosmosis • Four parts to ATP synthase:
Rotor, Stator, Rod, Knob • H+ must enter matrix here • Generates 1 ATP per ~3.4 H+
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Cellular Respiration Summary of respiration
• Cells convert ~ 40% of energy in glucose to energy in ATP • Most fuel efficient cars convert only ~ 25% of gasoline energy
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Cellular Respiration - anaerobic
• no O2 – no oxidative phosphorylation • fermentation - extension of glycolysis • substrate-level phosphorylation only • need to regenerate e- carrier (NAD+)
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Cellular Respiration - anaerobic
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Cellular Respiration - anaerobic
• Types of fermentation - 1. alcohol • pyruvate converted to acetaldehyde • acetaldehyde accepts e- • ethanol produced
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Cellular Respiration - anaerobic
• Types of fermentation - 2. Lactic acid • pyruvate accepts e- • lactate produced
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Cellular Respiration - anaerobic
• inputs/outputs • alcohol • pyruvate in • CO2 and EtOH out • brewing & baking • lactic acid • pyruvate in • lactate out • muscle fatigue
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Cellular Respiration • pyruvate - junction
• O2 present – citric acid cycle • O2 absent - fermentation
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Self-Check • Comparison of aerobic vs. anaerobic respiration:
Aerobic Anaerobic • ATP made by: • ATP per glucose: • initial e- acceptor: • final e- acceptor:
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Cellular Respiration – other biomolecules
• Glucose catabolism = one option Cycle can run in reverse! • Proteins: – amino group removed – a.a. enter Krebs Cycle
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Cellular Respiration – fats
Glycerol in at glycolysis - becomes pyruvate Fatty acids at coenzyme junction - becomes Acetyl CoA 2 carbons at a time via β-oxidation A fatty acid chain of 16 C is energetically equivalent to how many glucose molecules?
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Self-Check Step of Respiration Inputs Outputs CO2/H2O ATP produced
e- carriers loaded Glycolysis 1 glucose 2 pyruvate 2H2O 2 net 2 NADH Coenzyme Junction Citric Acid Cycle Electron Transport Chain Oxidative phosphorylation Fermentation
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Lecture 2 Summary 1. Respiration Overview (Ch. 7) Purpose
Redox reactions Electron carriers & final electron acceptors 2. Locations of respiration steps, inputs/outputs, purpose, description (Ch. 7) Glycolysis Coenzyme Junction Citric Acid/Krebs Cycle ETC & Oxidative Phosphorylation [chemiosmosis] 3. Differences with anaerobic respiration (Ch. 7) Location Inputs/outputs 4. Catabolism of other biomolecules (Ch. 7) Proteins Fats
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