[Aiyume]

I have questions about glycolysis, and I tried to answer them. I need someone to look at my answer and see if they are correct or not. Especially questions 7 and 8. Thanks!

1) Is the conversion of 2-phosphoglycerate to phosphoenolpyruvate a redox reaction?
Ans: No, because there is no transfer of electrons.

2) Explain how fructose catabolism may lead to an overproduction of pyruvate relative to glucose metabolism in the liver.
Ans: PFK-1 is the major control step in glycolysis where many factors in glucose metabolism would regulate this step, but fructose could bypass PFK-1 to produce pyruvate.

3) Illustrate how increased intracellular [cAMP] affects the activity of pyruvate kinase in mammalian liver cells.
Ans: Low blood glucose --> Glucagon release --> increase cAMP --> activates PKA --> decrease glycogen synthesis

4) Ingestion of large amounts of ethanol inhibits glycolysis. Which glycolytic enzyme is inhibited? Why?
Ans: Lactate dehydrogenase is inhibited.
Because: Ethanol + NAD+ ---> CH3CHO + NADH + H+
Decrease [NAD+]/ [NADH] ratio, inhibit transformation of lactate to pyruvate.

5) In an anaerobic muscle preparation, lactate formed from glucose labeled in C-3 and C-4 would be labeled in __________
Ans: the methyl and carboxyl carbon atoms

6) A new dehydrogenase enzyme catalyzing the conversion of glyceraldehyde 3-phosphate to phosphoglycerate directly. How would modifying the glycolytic pathway in this way affect the cell?
Ans: It bypass a step; normally it would be:
GAP + Pi + NAD+ ----> 13BPG + NADH + H+ delta G = +6.3kJ/mol
1,3BPG + ADP ----> 3PG + ATP delta G = -18.5kJ/mol ==> delta G = -12.2kJ/mol
Bypassing the step that produce 13BPG, delta G could be more negative - more energy is produced.

7) State the fate of 32Pi that is added to a cell-free liver preparation undergoing glycolysis.
Ans: It will be used in early step to provide energy for starting glycolysis, then it will be regenerated at the end of glycolysis.

8 ) If patients with diabetes mellitus produce insufficient insulin, explain why these patients cannot properly respond to increases in the levels of blood glucose
Ans: High blood glucose ---> insulin secreation ---> Actived phosphatase ---> activate PFK2, inactivate FBPase-2 ----> increase [F-2,6BP] ---> Activate PFK 1, inactivate FBPase-1 ----> Increase glycolysis, decrease glyconeogensis
Patients with diabetes mellitus cannot produce sufficient insulin, therefore, glucose uptake is slow.