Q1. Calculate the ratio of phosphoenolpyruvate to pyruvate in the human erythrocyte, necessary to convert pyruvate back to phosphoenolpyruvate. The concentrations of ADP and ATP in human erythrocytes are 0.25 mM and 2.25 mM respectively and the ΔG0' for the reaction is -1.4 kJ/mol

Q2. First bypass: Pyruvate to oxaloacetate to phosphoenolpyruvate

a. If you incubate bacteria with pyruvate and [14C}-HCO3, indicate the carbons the would be radioactively labeled in oxaloacetate, and in phosphoenolpyryuvate

b. If you incubate bacteria with [14C]-pyruvate (the radioactive labeled carried by the C in the CH3 group), which carbons would be labeled in

- OA

- Pyruvate

- Glucose.

Q3. Identify the reaction catalyzed by pyruvate carboxylase as a reduction or oxidation.

This reaction requires biotin. How many molecules of biotin are covalently attached to the enzyme?

What may happen if the (-CH2-)4  is "rigidified" replacing one of the single C-C bonds with a double bond?

Q4. Oxalacetate cannot get into the mitochondria and should be transformed into L-malate.

Is this a reduction or an oxidation?

What is the standard free energy for this reaction? Under physiological conditions, this reaction is very close to equilibrium. Provide a reason.

What is the importance of regeneration of oxalacetate from L-malate in the cytoplasm?

Q5. Draw an energy diagram for the reaction of Pyruvate->oxaloacetate->Phophoenolpyruvate.

Q6. How many molecules of ATP, GTP, and NADH are consumed to produce glucose from

a. Glyceraldehyde- phosphate

b. Fructose-1, 6, bisphosphate