Although the final reaction of the hexose portion of glycolysis yields DHAP and

Question

Although the final reaction of the hexose portion of glycolysis yields DHAP and G-3-P, further reactions proceed as if there had been 2 G-3-P made per glucose. Why?
a. G-3-phosphate is used for Stage II of glycolysis so the system is more likely to produce more of it than Dihydroxyactone phosphate.

b. Because the Go of the conversion between the two is negative.

c. Because the Go of the conversion between the two is positive

d. Because nonequililbrium conditions favor the conversion of DHAP to G-3-P

e. None of the above

Explanation / Answer

Answer: a

Glyceraldehyde-3-phosphate is directly used in the second phase of glycolysis since it produces ATP, but dihydroxyacetone phosphate does not. Dihydroxy acetone phosphate cannot enter the phase 2 of glycolysis unless it is coverted to Glyceraldehyde-3-phosphate. These two forms are easily convertible by TIM (Triose phosphate isomerase) and most of it remains in the form of G-3-phosphate. If dihydroxyacetone phosphate is not converted to G-3-phosphate, the energy pruduction (ATP generation) is compromised.

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