Name______________________

 

Part I: Short answer. Please write complete sentences. Draw structures when appropriate. Each question is worth 5 points.

1. Why does the HIV virus only invade T lymphocytes and phagocytes?

 

 

 

 

 

2. Why is cholesterol essential for proper membrane structure and function?

 

 

 

 

3. Give an example of each type of signal transduction system that we have studied so far.

 

 

 

 

 

 

 

 

4. Describe the effect that an enzyme has on the ΔG of a reaction.

 

 

 

 

 

 

5. Draw a picture showing the cascade of signals that occurs when epinephrine binds to its receptor on a muscle cell.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Part II. Calculations. Put a box around your final answer. Each question is worth 10 points.

6. How much energy is required to increase the sodium concentration inside a cell to 30 times greater than the concentration outside of a cell at 25EC? The cell potential is 50 mV, (inside is negative).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

7. The energy for the synthesis of ATP in the mitochondria comes from the pH gradient that exists across the inner mitochondrial membrane. Protons move out of the matrix and into the inner membrane space via several mechanisms. If the pH of the mitochondrial matrix is 7.6 and the pH of the inner membrane space is 7.2, what is the ΔG for the movement of protons out of the matrix? The membrane potential is -0.070V (inside is negative). The temperature is 37EC.

 

 

 

 

 

 

 

 

 

 

8. Ubiquinone is an important part of the electron transport chain. It receives electrons and then donates them to other electron acceptors. Use the equations below to answer the following questions:

a. Write a redox equation using Ubiquinone as the oxidizing agent.

b. Calculate the Keq for the reaction that you wrote. ( 25EC)

c. Put a box around the reducing agent.

 

Half reactions Reduction potentials (E=E, Volts)

Fe+3 + e -1 ------> Fe+2 0.771

Ubiquinone + 2H+ + 2 e -1 ------ubiquinol + H2 0.045

NAD + 2H+ + 2e- ----------> NADH, H+ -0.320

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

9. ATP is synthesized in one glycolysis reaction. The phosphate from phosphoenol pyruvate(PEP) is transferred to ADP to make pyruvate and ATP. This is known as substrate level phosphorylation.

a. Calculate the free energy change at 37EC for the conversion of phosphoenol pyruvate (PEP) to pyruvate and the synthesis of ATP using the following concentrations and standard free energies.

 

b. Is this reaction at equilibrium? Why or why not?

 

pyruvate = 0.051mM

phosphoenol pyruvate = 0.023 mM

ATP = 2.24 mM

ADP = 0.25 mM

 

phosphoenol pyruvate-------------> pyruvate ΔG=E = -31.4 kJ/mol

ADP + Pi -------------> ATP ΔG=E = 30.5 kJ/mol

 

 

 

 

 

 

 

 

 

 

 

 

 

Part III, Short Essay: Your answer should be written in complete sentences that are in well organized paragraphs. If you don=t want a portion to be graded, just put a line through it and I will not read it. Questions will be graded on content (14 points), organization ( 4 points), grammar (2 point). I realize these are rough drafts and I will fully consider that when I grade these. Each question is worth 20 points.

 

10. Describe how the pancreas, liver, muscle and fat tissues are involved in maintaining blood glucose. Be sure to include what receptors are present, what transporters are involved, how the receptors and transporters function in each cell. Also, how are the receptors and transporters regulated?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

11. Epinephrine binds to a receptor on a muscle cell and activates a cascade that ultimately triggers the hydrolysis of glycogen. The seratonin receptor is similar, but uses different second messengers to propagate the signal.

a. For each type of receptor, describe how it works.

b. What second messenger(s) is/are involved for each?

c. How is the signal turned off for each receptor

d. What are the advantages to this type of signal mechanism?