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IB HL Biology 8.2 Cell Respiration (Mitochondria: in all eukaryotic cells;…

- - - - Cellular respiration: controlled release of energy from organic compounds to produce ATP
        
        Types
        
        Aerobic respiration: complete breakdown, oxygen required, large ATP yield
        
        Anaerobic respiration: incomplete breakdown, no oxygen required, small ATP yield
        
        Discrete steps
        
        Activation energy divided across steps (can be reached @ normal body temperatures)
        
        Released energy transferred to activated carrier molecules via redox reactions to make ATP
        
        Redox reactions: reduction of one species and oxidation of another
        
        Reduction
        
        Gain electrons
        
        Gain hydrogen
        
        Lose oxygen
        
        Oxidation
        
        Lose electrons
        
        Lose hydrogen
        
        Gain oxygen
        
        Carrier molecules (hydrogen or electron carriers) b/c they gain e-'s and p+'s; transport them to cristae (site of ETC in mitochondria) where they are used to synthesize ATP (requires oxygen → why aerobic respiration unlocks more energy and produces more ATP)
        
        NAD+ - reduced to form NADH (NAD+ + 2H+ + 2e- → NADH + H+)
        
        FAD reduced to form FADH2 (FAD + 2H+ + 2e- → FADH2)
- - - - LINK REACTION: transport of pyruvate into mitochondria; 1) pyruvate transported from cytosol into mitochondrial matrix by carrier proteins on mitochondrial membrane, 2) pyruvate is decarboxylized → CO2 formed, 3) 2C forms acetyl group when it loses H atoms via oxidation (NAD+ reduced to NADH + H+), 4) acetyl compound combines with coenzyme A to form acetyl CoA; glycolysis splits glucose into two pyruvate molecules therefore link reaction occurs twice per glucose molecule (PRODUCTS: 2x acetyl CoA, 2x NADH + H+, 2x CO2)
        
        KREBS CYCLE/CITRIC ACID (mitochondrial matrix): 1) acetyl CoA transfers acetyl group to oxaloacetate to make citrate (4C to 6C compound); CoA released and returns to link reaction fo form more acetyl CoA, 2) 6C compound broken down - 2 C atoms released via decarboxylation to form 2x CO2, 3) reduction of hydrogen carriers (3x NADH + H+, 1 x FADH2), 1 ATP formed from SLP; link reaction produces two acetyl CoA molecules therefore Krebs occurs twice (4x CO2, 2x ATP, 6x NADH + H+, 2x FADH2)
        
        ELECTRON TRANSPORT CHAIN (inner mitochondrial membrane arranged into cristae/folds to increase SA): 1) generating proton motive force - hydrogen carriers oxidized and release high energy e- and p+'s → e-'s transferred to ETC consisting of transmembrane carrier proteins, as they pass through lose their energy which is used by chain to pump H+ ions from matrix: this accumulation w/in intermembrane space creates electrochemical gradient/proton motive force, 2) ATP synthesis (chemiosmosis) - proton motive force causes H+ ions to move down gradient and diffuse back into matrix (chemiosmosis) as facilitated by ATP synthase enzyme (trigger molecular rotation/phosphorylation to synthesize ATP), 3) reduction of oxygen - oxygen acts as final e- acceptor, removing de-energized e-'s to prevent chain from being blocked/binds with free p+'s to form H2O (removing protons maintains H gradient), WITHOUT OXYGEN, CARRIERS CANNOT TRANSFER ENERGIZED ELECTRONS TO CHAIN AND ATP PRODUCTION STOPPED
    - - Animals - converted to lactic acid
      - Plants/yeast - converted into ethanol and CO2 (used in bread and alcohol)
      - *glycolysis involves rxn's to reduce NAD+ to NADH and H+
        
        Reduced hydrogen carriers oxidized via aerobic respiration to restore NAD+ stocks
        
        Glycolysis depletes available stocks of NAD+, preventing further glycolysis in anaerobic respiration → fermentation of pyruvate involves reduction rxn that oxidizes NADH and allows glycolysis to continue without oxygen
- - - - Anaerobic: glucose
      - Aerobic: glucose and oxygen
    - - Anaerobic: incomplete
      - Aerobic: complete
    - - Anaerobic: 2 ATP
      - Aerobic: 36-38 ATP
    - - Anaerobic: lactic acid (animals), ethanol and CO2 (yeast)
      - Aerobic: CO2, H2O
    - - Anaerobic: cytoplasm
      - Aerobic: cytoplasm, mitochondrion
    - - Anaerobic: glycolysis, fermentation
      - Aerobic: glycolysis, link reaction, Krebs cycle, ETC
  - - - Temperature
      - Hydration
      - LIght