Glyceraldehyde-3-phosphate dehydrogenase catalyzes the sixth step in glycolysis; the conversion of glyceraldehyde-3-phosphate (G3P) into 1,3-bisphosphoglycerate (1,3BPG).

G3P + NAD+ + Pi ï 1,3BPG + NADH + H+ a)

a) How do we know that this is an oxidation-reduction reaction?

b) Write out the two reductive half reactions and indicate E0â for each half reaction.

c) Under biological standard state conditions, what is the free energy change (DG0â)? Which direction is spontaneous?

d) The cellular ratio of [NAD+] to [NADH] is ~1000 to promote catabolism. With cellular conditions of [G3P] and [1,3BPG] = 1mM and [Pi ] = 50 mM, what is DGâ for the reaction?

Indicate the direction in which the reaction is spontaneous under these cellular conditions.

Question

Glyceraldehyde-3-phosphate dehydrogenase catalyzes the sixth step in glycolysis; the conversion of glyceraldehyde-3-phosphate (G3P) into 1,3-bisphosphoglycerate (1,3BPG).

G3P + NAD+ + Pi ï 1,3BPG + NADH + H+ a)

a) How do we know that this is an oxidation-reduction reaction?

b) Write out the two reductive half reactions and indicate E0â for each half reaction.

c) Under biological standard state conditions, what is the free energy change (DG0â)? Which direction is spontaneous?

d) The cellular ratio of [NAD+] to [NADH] is ~1000 to promote catabolism. With cellular conditions of [G3P] and [1,3BPG] = 1mM and [Pi ] = 50 mM, what is DGâ for the reaction?

Indicate the direction in which the reaction is spontaneous under these cellular conditions.

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