Oxidative phosphorylation (respiration)
- 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.
- Electron transport chain
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