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Anaerobic Respiration
- when oxygen is not present
- - ex: Fermentation
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Fermentation
- occurs instead of cellular respiration
- incomplete oxidation (giving less ATP)
- waste products: CO2 and lactic acid or ethanol
- produces 2 ATP
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Aerobic Respiration
- when oxygen is present
- consumes organic molecules and O2 and yields ATP
- C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy
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Oxidative Phosphorylation
- making ATP via electron transport chain by adding Phosphate
- requires oxygen and electron transport chain
- ex: in photosynthesis b/t photosystem II and I
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Substrate Level Phosphorylation
- making ATP from a substrate
- no electron transport chain
- no oxygen
- less ATP made
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NAD+
- coenzyme; electron acceptor
- passes electrons to electron transport chain
- NADH = reduced form of NAD+
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Glycolysis
- First phase of aerobic respiration
- Breaks down glucose into two molecules of pyruvate
- Takes place outside of mitochondria, in cytosol
- Makes 2 pyruvates, 2 NADH, and 4 ATP by substrate-level phosphorylation
- Uses glucose and 2 ATP
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Citric Acid (Kreb's) Cycle
- completes the breakdown of glucose
- Gain 1 ATP per cycle - 2 pyruvates formed during glycolysis, so must go around cycle 2 times = 2 ATP (by substrate-phosphorylation)
- in mitochondria region
- more electrons added from glycolysis
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Kreb's Cycle (cont.)
- releases a TOTAL of:
- 4 CO2 (other 2 CO2 needed for product comes from the change into pyruvate)2 ATP
- 6 NADH
- 2 FADH21 molecule pyruvate releases:
- 2 CO2
- 1 ATP
- 3 NADH
- 1 FADH2
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Electron Transport Chain
- Following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the energy extracted from food
- These 2 e- carriers donate e-s to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation
- slow release of a little energy at a time; controlled
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Electron Transport Chain (cont.)
- Electrons are passed through a number of cytochromes (proteins with iron atom that accept and donate electrons) to O2
- Function: to break the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts
- Releases 32-34 ATP
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Chemiosmosis
- use of energy in H+ gradient to drive cellular work
- Electron transfer causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space
- H+ moves back across the membrane through channels in ATP synthase
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Fermentation and anaerobic respiration
- Glycolysis can produce ATP with or without O2
- Anaerobic respiration uses electron transport chain with electron acceptor other than O2
- Fermentation uses phosphorylation instead of electron transport chain
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Why do fermentation?
- To get rid of pyruvate - waste product can get out of the cell
- Continue making ATP & NADH from glycolysis
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Fermentation and Aerobic Respiration
- Both use glycolysis
- Different final electron acceptors
- Different amounts of ATP produced (Aerobic = 38 ATP per glucose molecule; Fermentation = 2 ATP per glucose molecule)
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Why is Oxygen needed?
- It is the final electron acceptor in electron transport chain
- For pull of pyruvate into mitochondria (changing to CoA)
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