Metabolism
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Experiments on glucose metabolism
Key points from this exercise:
The metabolism of glucose can occur anaerobically, leading to the formation of 2 mol of lactate per mol of glucose.
Two mol of ATP are required to form fructose 1,6-bisphosphate from glucose.
Fructose 1,6-bisphosphate is cleaved to dihydroxyacetone phosphate and glyceraldehyde 3-phosphate, which are interconvertible.
Glyceraldehyde 3-phosphate undergoes oxidation (linked t the reduction of NAD to NADH) and phosphorylation (using inorganic phosphate) to form 1,3-bisphosphoglycerate.
One phosphate esterified to 1,3-bisphosphoglycerate is transferred to ADP, forming ATP.
Following a series of isomerisation reactions, phosphoenolpyruvate is formed, and its phosphate is also transferred to ADP forming ATP.
Under anaerobic conditions the NADH formed by oxidation of glyceraldehyde 3-phosphate is re-oxidised by reducing pyruvate to lactate. (The fate of pyruvate under aerobic conditions will be considered in a later exercise.)
Because there are two 3-carbon sugars formed from each mol of glucose, there is a yield of 4 x ATP per glucose metabolised. The 2 mol of ATP required to form fructose 1,6-bisphosphate from glucose must be subtracted from this, so there is a net yield of 2 x ATP per mol of glucose metabolised under anaerobic conditions.
Under aerobic conditions the NADH formed can be re-oxidised in the mitochondrial electron transport chain, yielding an additional ~2.5 x ATP per NADH, and so an additional ~5 x ATP per glucose.