Question

GAP is the only 3 atom unit useful to produce ATP. However, under cellular conditions, TPI favors DHAP formation over GAP formation. How can glycolysis work? A. Glycolysis reactions that occur in stage 3, lower the concentration of GAP and drive glycolysis B. Aldolase reaction favors GAP formation C. ATP hydrolysis in stage 1 are irreversible and favor the formation of GAP D. TPI changes the equilibrium to favor GAP formation E. All of the above

Answer 1

It is well known that the concentration GAP is lowered from step 6, whereas in stage 3 fructose 6-phosphate converted into fructose 1,6-bisphosphate. Hence, option A is wrong.

In stage 1,   the glucose ring is phosphorylated in presence of ATP where as GAP is formed in stage 4 during aldose reaction and the phosporylation is not an irreversible reaction. so, option C is not right.

In case of step 4 of glycolysis, the enzyme Aldolase splits fructose 1, 6-bisphosphate into two isomer dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP), so there is no favorable reactions for GAP formation. so, option B is wrong.

From step 5 of glycolysis, GAP is the only molecule that continues in the glycolytic pathway. As a result, all of the DHAP molecules produced in the previuos step, are further converted to GAP by the enzyme TPI. So, TPI change the equlibrium to favor GAP formation. hence, option D is right.