gluconeogenesis from pyruvate--> labeling carbon

[nickname]

I have to predict the positions of the glucose molecule that would become labeled from the 1-14C pyruvate (i.e, the label in the carboxyl group of pyruvate).

a) Carbon-1

b) carbon-2

c) carbon-3

d) carbon-4

e) carbon-5

d) carbon-6

I first thought that carbons 1 and 6 were the correct answers, but they are not. Then I thought that 1,3,and 6 were correct but they are not. I know that pyruvate has 3 carbons and glucose has 6, but I know two how to approach this problem correctly. Any help will be appreciate it.

Thank you and happy holidays!

[JackBean]

look on the reactions, which take place in gluconeogenesis and their mechanism. It's quite simple to trace the labeled atom...

[nickname]

So for this kind of problem you look at where the new carbon is being attached to, correct?

[JackBean]

look on this picture: http://upload.wikimedia.org/wikipedia/e ... enesis.png
and trace your atom! Just be carefull about symetrical molecules!

[USFBiomed]

3,4... its a head to head bonding, not tail to tail, so 1,6 would be the reverse...

[nickname]

Thank you USFBiomed. So since pyruvate is 3 carbons and glucose is 6 I connect the last of pyruvate with the first incoming carbon atom so 3 and 4 like you said. Is this explanation correct? Thanks again for your help and happy holidays!