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level: 12.3 Oxidative phosphorylation

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level questions: 12.3 Oxidative phosphorylation

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Oxidative phosphorylation- The last stage of aerobic respiration - Inner mitochondrial membrane - Produces many molecules of ATP + produces H20 from O2
Reactants​- NADH - FADH2
Products- H20 - Energy - ATP
The current model for oxidative phosphorylation- Chemiosmotic theory
Chemiosmotic theory- Energy from electrons passed through the ETC is used to pump H ions up their con. g. into the intermembrane space - The Hs are then allowed to flow by facilitated diffusion through ATP synthase into the matrix - Energy of the H2 flowing down their con. g. is harnessed resulting in the conversion of ADP into ATP by ATP synthase
The electron transport chain (ETC)- Made up of a series of membrane proteins/electron carriers - Positioned close together which allows the electrons to pass from carrier to carrier - Inner membrane of the mitochondria is impermeable to H ions so these electron carriers are required to pump H across the membrane to establish the con. g.
An outline of oxidative phosphorylation (1)- H2 is donated by NADH + FADH2 from the KC - H2 split into protons (H+ ions) + electrons - Electrons enter the ETC in a series of oxidation-reduction reactions
An outline of oxidative phosphorylation (2)- Energy from electrons passed through the ETC is used to pump H ions up their con. g. into the intermembrane space - A con. g. of protons is established between the intermembrane space and the matrix
An outline of oxidative phosphorylation (3)- The Hs are then allowed to flow by facilitated diffusion through ATP synthase into the matrix - Energy of the H2 flowing down their con. g. is harnessed resulting in the conversion of ADP into ATP by ATP synthase - O2 acts as the 'final electron acceptor' + combines with protons and electrons at the end of the ETC to form H2O
Products from one Krebs cycle and where it goes- 1 coenzyme A, reduced in the next link reaction - Oxaloacetate, regenerated for use in the next Krebs cycle - 2 CO2, released as a waste product - 1 ATP, used for energy - 3 reduced NAD, to oxidative phosphorylation - 1 reduced FAD, to oxidative phosphorylation
Why is oxygen so important for aerobic respiration- Final electron acceptor - Without O2 ETC can't continue coz electrons have nowhere to go - Without O2 accepting e-s + Hs, NADH2 + FADH2 cannot be oxidised to NAD and FAD - So they can’t be used in further hydrogen transport
ATP production can be affected by mitochondria diseases- Affect how proteins involved in OP or KC function, reducing ATP production - This may cause anaerobic respiration to increase, to try and make up some of the ATP shortage - This results in lots of lactate being produced, causes muscle fatigue + weakness - Some lactate will also diffuse into the bloodstream, leading to high lactate concentrations in the blood
Releasing energy in stages- The more energy that is released in a single step, the more of it is released as heat, less available for more useful purposes - So, electrons carried by NAD + FAD are not transferred in one explosive step - Instead passed along a series of electron transfer carrier molecules, each of which is at a slightly lower energy level - The electrons move down an energy gradient - Which allows their energy to be released gradually + more usefully
Alternative respiratory substrates- Sugars are not the only substrates which can be oxidised by cells to release energy - Both lipids + proteins may be used as respiratory substrates, without first being converted to carbohydrate
Respiration of lipids- Trigs are hydrolysed to fatty acids + glycerol - Glycerol is converted to triose phosphate - Fatty acids hydrolyses into 2C fragments which are converted to acetylcoA - Enter KC - Energy yield is more that that of glucose respiration - As trigs have more Hs than glucose, thus it carries more electrons, so more energy
Respiration of protein- Hydrolysed into amino acids - Have amino acid groups removed (deamination) - 3C compounds converted to pyruvate - 4 + 5C compounds converted to intermediates in KC