(12) Respiration Flashcards
what happens during glycolysis
one molecule of glucose (6C) is split into 2 molecules of pyruvate (3C) in the cytoplasm of cells. this doesn’t require oxygen but is the 1st stage of anaerobic and aerobic
outline phosphorylation (the first stage of glycolysis)
1) phosphorylation- glucose is phosphorylated using a phosphate from a molecule of ATP which creates glucose phosphate and ADP. ATP is then used to add another phosphate to form hexose biphosphate which splits to form 2 molecules of triose phosphate.
outline oxidation (the second stage of glycolysis)
2) TP is oxidised (loses hydrogen) forming 2 molecules of pyruvate.
NAD collects H+ forming 2 x NADH
4 ATP are produced but 2 were used up in stage 1 so theres a net gain of 2 ATP.
in aerobic respiration what happens to the products of glycolysis
the 2 molecules of NADH go to oxidative phosphorylation
the 2 pyruvate molecules are actively transported to the matrix of the mitochondria for the link reaction
what happens to pyruvate in anaerobic respiration
converted to ethanol (plants and yeast) or lactate (animals and some bacteria) using NADH
how does glycolysis continue when there isn’t much oxygen
production of ethanol or lactate regenerates oxidised NAD so glycolysis can continue so a small amount of ATP can be produced to keep some biological processes going
what happens in the link reaction
1) pyruvate is decarboxylated (one C atom removed in the form of CO2)
2) pyruvate is oxidised to form acetate and NAD is reduced to form NADH
3) acetate is combined with coenzyme A to form acetyl coenzyme A
4) no ATP is produced
how many times does the link reaction occur for every glucose molecule
twice
what happens in the krebs cycle (series of redox reactions in the matrix of the mitochondria)
1) acetyl CoA from link reaction combines with a 4C molecule to form 6C molecule. CoA goes back to link reaction to be used again
2) 6C citrate molecule is converted to 5C molecule. CO2 is removed (decarboxylation), hydrogen is removed (dehydrogenation). H is used to produce NADH
3) 5C molecule then converted to 4C molecule
decarboxylation and dehydrogenation occur producing one reduced FAD and 2 reduced NAD. ATP is produced by substrate level phosphorylation and citrate is now oxaloacetate.
what is substrate level phosphorylation
when a phosphate group is transferred directly from one molecule to another
what is the order of steps in aerobic respiration
- glycolysis (phosphorylation & oxidation)
- link reaction
- krebs cycle
- oxidative phosphorylation
what happens during oxidative phosphorylation
energy carried by electrons from reduced coenzymes (reduced FAD and NAD) is used to make ATP (involves electron transport chain and chemiosmosis
outline the steps of oxidative phosphorylation
1) H atoms are released from NADH and FADH and the H atoms split into protons and electrons
2) electrons move down ETC and lose energy
3) energy is used to pump protons from mitochondrial matrix into intermembrane space (forms conc gradient)
4) protons move back into mitochondrial matrix via ATP synthase. this drives the synthesis of ATP from ADP and Pi (this is called chemiosmosis)
5) in mitochondrial matrix at end of transport chain, protons, e- and O2 combine to form H2O. O2 is said to be the final electron acceptor.
what is chemiosmosis and the chemiosmotic theory
chemiosmosis- process of ATP production driven by the movement of H+ ions across a membrane (due to electrons moving down electron transport chain)
how many ATP can be made from one glucose molecule
32
