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Cellular Respiration Harvesting Chemical Energy
ATP
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Overview of cellular respiration
1. Glycolysis – occurs in cytoplasm Anaerobic respiration - respiration without O2 Aerobic respiration - respiration using O2 - in cytoplasm - in mitochondria 2. Lactic Acid Fermentation OR Alcoholic Fermentation 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain C6H12O6 6O2 ATP 6H2O 6CO2 +
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Cellular Respiration Stage 1: Glycolysis
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What’s the point? The point is to make ATP! ATP
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glucose pyruvate
Glycolysis Breaking down glucose “glyco – lysis” (splitting sugar) ancient pathway which harvests energy Is the starting point for ALL cellular respiration but it’s inefficient generate only 2 ATP for every 1 glucose occurs in cytoplasm glucose pyruvate 2x 6C 3C Why does it make sense that this happens in the cytosol? Who evolved first? That’s not enough ATP for me!
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Overview 10 reactions glucose C-C-C-C-C-C fructose-1,6bP
ATP 2 enzyme 10 reactions convert glucose (6C) to 2 pyruvate (3C) produces: 4 ATP & 2 NADH uses: 2 ATP End result: 2 ATP & 2 NADH ADP 2 enzyme fructose-1,6bP P-C-C-C-C-C-C-P enzyme enzyme enzyme DHAP P-C-C-C G3P C-C-C-P NAD+ 2 2H 2Pi enzyme 2 1st ATP used is like a match to light a fire… initiation energy / activation energy. Destabilizes glucose enough to split it in two enzyme ADP 4 2Pi enzyme ATP 4 pyruvate C-C-C
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Overview of cellular respiration
1. Glycolysis – occurs in cytoplasm Anaerobic respiration - respiration without O2 Aerobic respiration - respiration using O2 - in cytoplasm - in mitochondria 2. Lactic Acid Fermentation OR Alcoholic Fermentation 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain C6H12O6 6O2 ATP 6H2O 6CO2 +
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Cellular Respiration Stage 2 & 3: Oxidation of Pyruvate Krebs Cycle
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Cellular respiration
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Mitochondria — Structure
Double membrane energy harvesting organelle smooth outer membrane highly folded inner membrane cristae intermembrane space fluid-filled space between membranes matrix inner fluid-filled space intermembrane space inner membrane outer matrix cristae mitochondrial DNA
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pyruvate acetyl CoA + CO2
Oxidation of pyruvate Pyruvate enters mitochondrial matrix As it enters…. Breaks off a carbon and makes 2 CO2 Makes 2 NADH produces 2 acetyl CoA molecules Acetyl CoA enters Krebs cycle [ 2x ] pyruvate acetyl CoA + CO2 3C NAD 2C 1C Where does the CO2 go? Exhale! CO2 is fully oxidized carbon == can’t get any more energy out it CH4 is a fully reduced carbon == good fuel!!!
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Pyruvate is a branching point
fermentation anaerobic respiration mitochondria Krebs cycle aerobic respiration
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Count the electron carriers!
pyruvate 3C 2C acetyl CoA NADH NADH citrate 4C 6C 4C 6C This happens twice for each glucose molecule CO2 Everytime the carbons are oxidized, an NAD+ is being reduced. But wait…where’s all the ATP?? NADH x2 5C 4C FADH2 CO2 4C 4C NADH ATP
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Krebs Cycle So we fully broke down glucose C6H12O6 CO2
& ended up with 2 more ATP! What’s the point?
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Electron Carriers = Hydrogen Carriers
Krebs cycle produces large quantities of electron carriers NADH FADH2 go to Electron Transport Chain! ADP + Pi ATP
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Energy accounting of Krebs cycle
2x 4 NAD + 1 FAD 4 NADH + 1 FADH2 pyruvate CO2 1 ADP 1 ATP 3C 3x 1C ATP Net gain = 2 ATP = 8 NADH + 2 FADH2
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Overview of cellular respiration
1. Glycolysis – occurs in cytoplasm Anaerobic respiration - respiration without O2 Aerobic respiration - respiration using O2 - in cytoplasm - in mitochondria 2. Lactic Acid Fermentation OR Alcoholic Fermentation 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain C6H12O6 6O2 ATP 6H2O 6CO2 +
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Cellular Respiration Stage 4: Electron Transport Chain
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Cellular respiration
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What’s the point? The point is to make ATP! ATP
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ATP accounting so far… Glycolysis 2 ATP Kreb’s cycle 2 ATP
Life takes a lot of energy to run, need to extract more energy than 4 ATP! There’s got to be a better way! I need a lot more ATP! A working muscle recycles over 10 million ATPs per second
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That sounds more like it!
There is a better way! Electron Transport Chain series of proteins built into inner mitochondrial membrane transport of electrons down ETC that bring Hydrogen ions across the membrane These hydrogen electrons fuel a protein that makes ATP This stage makes ~36 ATP from 1 glucose! Only happens WITH O2 (aerobic respiration) That sounds more like it! O2
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Remember the Electron Carriers?
Krebs cycle 8 NADH 2 FADH2 Time to break open the piggybank!
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Electron Transport Chain
Building proton gradient! NADH NAD+ + H p e intermembrane space H+ H+ H+ inner mitochondrial membrane H e- + H+ C Q e– e– e– H FADH2 FAD H 1 2 NADH 2H+ + O2 H2O NAD+ As NADH and FADH2 move through the proteins, they drop off hydrogen and make water NADH dehydrogenase cytochrome bc complex cytochrome c oxidase complex mitochondrial matrix
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We did it! Set up a H+ gradient They want to move from high to low
ADP + Pi Set up a H+ gradient They want to move from high to low As they move to low the protons to flow through ATP synthase Synthesizes ATP ADP + Pi ATP ATP
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~40 ATP Cellular respiration + + 2 ATP 2 ATP ~36 ATP
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Overview of cellular respiration
1. Glycolysis – occurs in cytoplasm Anaerobic respiration - respiration without O2 Aerobic respiration - respiration using O2 - in cytoplasm - in mitochondria 2. Lactic Acid Fermentation OR Alcoholic Fermentation 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain C6H12O6 6O2 ATP 6H2O 6CO2 +
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Pyruvate is a branching point
fermentation anaerobic respiration mitochondria Krebs cycle aerobic respiration
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Fermentation (anaerobic)
Bacteria, yeast 1C 3C 2C pyruvate ethanol + CO2 NADH NAD+ back to glycolysis beer, wine, bread Animals, some fungi Count the carbons!! Lactic acid is not a dead end like ethanol. Once you have O2 again, lactate is converted back to pyruvate by the liver and fed to the Kreb’s cycle. pyruvate lactic acid 3C NADH NAD+ back to glycolysis cheese, anaerobic exercise (no O2)
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Alcoholic Fermentation
Takes pyruvate and makes ethanol (alcohol) and carbon dioxide Happens without oxygen but makes very little ATP Used by bacteria and yeast
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Lactic Acid Fermentation
Takes pyruvate and makes lactic acid Lactic acid is what makes your muscles sore This is eventually broken down over time and removed as waste Happens without oxygen but makes very little ATP Used by animals and some fungi
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