Please do not forget to write down all the names of your groupmembers.

1. Please propose the mechanism for α−β C-C bond cleavage ofG6P. Draw the mechanism clearly, give the structures of theproduct, and then explain why steps 2 and 3 of glycolysis arenecessary.

2. If glucose is labeled at C1 carbon (the C1 carbon is taggedwith radioactive 14C), where would this labeled C atom be (whichcarbon atom number, draw the structure and label this carbon atom)when glucose has been metabolized to:

A. DHAP

B. GAP (you should be able to figure which carbon atom is theoriginal C1 if you draw the mechanism of step 5)

C. After the reaction with G6PD enzyme (first step in pentosephosphate pathway)

D. After the oxidative decarboxylation step in PPP

E. How many % of the total pyruvate produced via glycolysis willcarry this label?

3. A. What would be the fate of glucose in cells that need ATP,but not NADPH and R5P?

B. How about cells that need a lot of NADPH, but not R5P?

C. Finally, what would be the fate of glucose if the cells needa lot of R5P, but not NADPH?

Here are some hints to help you answer Q3.

1) Remember that the reactions in PPP (with the exception of the3 in oxidative phase) are FULLY reversible.

2) Remember that glycolysis and PPP are linked by the commonmetabolites: F6P and GAP.

3) Although the stoichiometry of the reactions shown in class isdifferent: glycolysis starts from 1 glucose molecule and PPP needs3 G6P. In reality, our cells will always have more than 1 glucosemolecule. 180 g of glucose (4.5 cans of soft drink) is 6.022 x 1023molecules of glucose. Bottom line: to answer Q3, please do notworry about stoichiometry and whether there is enough glucose inthe cells or not. There is truly plenty of glucose to go to anypathways as needed.

UPDATE: Question 2 refers to question 1