Oxidative phosphorylation (respiration)

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  • Created by: Steff06
  • Created on: 26-02-16 11:09
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  • Oxidative phosphorylation
    • Electron transport chain
      • Takes place on CRISTAE of mitochondria. Carrier proteins are called CYTOCHROMES and arranged within cristae MEMBRANESin order of DECREASING energy levels.
      • OXYGEN acts as terminal ELECTRON ACCEPTOR.
      • 1. REDUCED NAD is DEHYDROGENATED, loses H+ ions. H+ ions split into PROTONS + ELECTRONS. Electrons pass down ETC, LOSING energy as they do so.
      • 2. Energy picked up by PROTEINS which use it to pump PROTONS into INTER MEMBRANE SPACE.
      • 3. Produces ELECTRO CHEMICAL GRADIENT. Protons DIFFUSE through ATP SYNTHASE back into mitochondrial MATRIX.
      • 4. Protons BIND with ELECTRONS and OXYGEN to produce WATER.
      • If the ETC is not operating as quickly as it should, NADH is NOT oxidised back to NAD/ The small amount of NAD within the cell will be used up. This will STOP conversion of TP to PYRUVATE.
    • Anaerobic respiration
      • LACK of oxygen, build up of LACTIC ACID and oxygen debt. Causes muscle FATIGUE.
      • Short burst activities, produces SMALL amounts of ATP.  1st part is GLYCOLYSIS which occurs in cell CYTOPLASM. Lactic acid BROKEN DOWN using OXYGEN in liver + muscle cells.
    • NAD/FAD:
      • Dehydrogenation occurrs where NAD/FAD/NADP are COENZYMES which ACCEPT hydrogen atoms. They take H+ ions to the ETC where they are SPLIT.
      • If oxidative phosphorylation couldnt occur, oxidised NAD/FAD amounts would DECREASE and reduced NAD/FAD amounts would increase.
    • Coenzyme A (CoA):
      • Helps in carrying ACETATE groups from PYRUVATE + carries acetate groups from fatty acids/amino acids to the KREBS CYCLE.
    • Cellular respiration:
      • ANAEROBIC respiration allows ATP to continue to be GENERATED when oxygen is LIMITING.
    • When free OXYGEN is LIMITING HYDROGENS cannot be disposed of by combining with OXYGEN and so the ETC is INHIBITED.
      • GLYCOLYSIS can still be used to make ATP. If a cell is to make the 2ATP made by glycolysis, the reduced NAD has to be OXIDISED. Do with ALCOHOLIC or LACTATE FERMENTATION.
    • ALCOHOLIC FERMENTATION:
      • Without oxidative phosphorylation, will RUN OUT of oxidised NAD.PYRUVATE is converted o ETHANAL. Reaction is catalysed by enzyme PYRUVATE DECARBOXYLASE. ETHANAL ACCEPT HYDROGEN from REDUCED NAD, which is REoxidised as ETHANAL is REDUCED to ETHANOL.
    • LACTATE FERMENTATION:
      • REDUCED NAD must be REOXIDISED to NAD. PYRUVATE is the HYDROGEN ACCEPTOR. It accepts H+ from reduced NAD. NAD is now reoxidised and available to accept MORE H+ from glucose. GLYCOLYSIS can continue, generating ATP for muscle CONTRACTION.
    • Purpose of anaerboic pathways:
      • To PRODUCE ATP in absence of sufficient oxygen. To PRODUCE OCIDISED NAD to ACCEPT more HYDROGEN ions from glucose in glycolysis. To CONVERT LACTATE to PYRUVATE to enter the KREBS CYCLE.

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