Chapter 16 Practice problems.

1. Human brains require glucose or ketone bodies as their sources of energy. During times of fasting, the liver supplies the brain (via the blood) with glucose that it makes from oxaloacetate. If a person only has acetyl CoA (a product of fatty acid metabolism) and the Kreb=s cycle enzymes and the enzymes to make glucose from oxaloacetate, can this person=s liver supply the brain with glucose? Why or why not?

2. The Cori cycle is used to convert muscle lactate into pyruvate in the liver. How can pyruvate be used to increase the amount of oxaloacetate for glucose production in the liver? What enzyme(s) are required?

 

3. Fluoroacetate kills rats.

a. What Kreb=s cycle and glycolysis intermediates accumulate?

b. What enzyme(s) are inhibited?

c. Why is it fatal to rats?

4. Fully describe the regulation of pyruvate dehydrogenase.

 

5. A 55 year old patient complains of weakness and uncoordinated movements. On first examination, the uncoordination was linked to the smell of fermented fruits on the patient=s breath. A blood test was done, and the results showed that the patient had elevated levels of pyruvate and a-ketoglutarate. A review of the patient=s history showed that he had just consumed a large meal of turkey, mashed potatoes and bread.

What is deficient in this patient? Why is he deficient in this? Why does he have elevated levels of pyruvate and a-ketoglutarate? What treatment would you suggest?

 

 

 

6. Graphically show the regulation of citrate synthase by succinyl CoA under saturating concentrations of oxaloacetate. Why does Succinyl CoA regulate citrate synthase?

 

7. Calculate the DG for the conversion of acetyl CoA and oxaloacetate to citrate. The DG'°   for the reaction is -32.2 Kj/mol, Temp: 25°C, Oxaloacetate: 1µM, acetylCoA: 1µM, citrate: 220µM, CoASH: 65µM, pH: 7.0. What is favored, reactants or products?

8. Why is oxygen essential for the operation of the Kreb=s cycle?