Biochemistry II, Exam II,    2002                            Name___________________________

There are 100 regular points and 5 bonus points.

Exam Memory Bank: See exam I for examples of equations and constants that are given.

1. (4 points) Anaplerotic reactions are those that result in replenishing intermediates in the TCA cycle. Which of the following enzymes catalyze(s) (an) anaplerotic reaction(s)?

I. malate dehydrogenase         II. pyruvate carboxylase           III. pyruvate kinase     IV. PEP carboxykinase

a. I and III        b. II and IV                c. I, II and III               d. IV only                 e. none of these

2. (4 points) In the catalysis of a reaction, an enzyme

I. Increases the rate.           II. Increases the Keq.             III. Lowers the activation energy.
IV. Increases the rate and increases the Gibb=s free energy of the reaction.

a. I and III           b. I, II and III           c. IV only                  d. II and IV                e. None of these

3. (10 points) Choose one of the enzymes from the Kreb=s cycle that is regulated by allosteric interactions, covalent modification or both. Draw the structures of all of the reactants and products for the reaction that it catalyzes. Fully discuss how the enzyme is regulated. Give an example of a disease that results from a defect in that enzyme.

4. (10 points) 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? Be specific.

5. (15 points) Compare the net yield of ATP from the complete oxidation of hexanoic acid versus the complete oxidation of glucose. If you consider that each mole of ATP requires 51.8 KJ for its synthesis, do the values for the amount of ATP energy account for the caloric content of fat (hexanoic acid= 9kcal/gram) and (sugar glucose=4 Kcal/gram).

6. (10 points) Combine the Alanine-Glucose cycle and the Cori cycle in one picture. You can use names of compounds or draw the structures. For the key steps, please provide the name of the enzyme involved. Explain how these cycles exacerbate the hyperglycemic state in a diabetic patient.

7. (10 points) Dr. Science's "friend" found a wonder diet pill advertised on the www. The "friend" ordered the pills that guaranteed "weight loss for those who love their feed-sacks". Upon ingesting the pills, the "friend" became quite ill and had a body temperature of 40EC. Dr. Science determined that the diet drug chemical was 2,4 dinitrophenol.

a. How was 2,4-dinitrophenol responsible for the "friend's" illness? Be specific about what the chemical was doing to what system in the patient. You should describe the system.

b. What is the basis for using this chemical as a weight loss product?

c. The friend was taken to an emergency room and was miss-diagnosed as having an infection. Luckily, Dr. Science was able to intervene before Dr. Welbynot could inject the antibiotic, Valinomycin. What effects would Valinomycin (an ionophore) have had on this patient.

d. Would 2,4 dinitrophenol affect the ATP concentration in erythrocytes? Explain your answer.

8. (12 points) Complete the following table for the b-oxidation enzymes. The reactions are not in order.

 

Enzyme

Cofactor (s)

Structure of the product(s)

Thiolase

 

 

 

 

 

 

 

 

 

 

 

FADH2

 

 

Hydratase

 

 

 

9. (10points) Hibernating bears don=t get thirsty in the middle of their long winter=s nap. What reactions are used to generate water in these animals? Be specific.

Part II. Please answer each question using complete sentences in well organized paragraphs.

10. (10 points) Fats are not soluble in blood, thus they must be transported through the blood on various carriers. Dietary fat, mobilized fat from adipocytes and excess dietary fat are all transported on different carriers. Describe each type of carrier and the destination of each type of fat.

11. (10 points) Why is oxygen essential for the operation of the Kreb=s cycle? Answer this in terms of how all of the reactions in the Kreb=s cycle are regulated and how oxygen in involved in the overall process of metabolism. Be specific. (Use the back of this page.)