1. (4 pts.) a.  Tell WHY fluorescence recovery after photobleaching demonstrates that membranes are fluid.
 

b.  Tell why a single freeze fracture experiment does not demonstrate that membranes are fluid.
 

2. (6 pts.) Indicate whether the transition temperature will be higher, lower or stay the same for each of the following membranes (assume the temperature remains constant).

All 16 carbon fatty acid chains are converted to 22 carbon chains ___________________

All unsaturated fatty acids become fully saturated _______________________________

The number of membrane proteins increases by 10-fold __________________________

3. (6 pts.) Below is a diagram of and SDS-PAGE gel in which several mixtures of proteins were run in different lanes. In lane 1, a mixture of hemaglobin, myoglobin, albumen and collagen was run on the gel. The bands corresponding to each protein are indicated. In the other lanes were run:

2. Hemaglobin and myoglobin only 3. Myoglobin and albumen only 4. Myoglobin, albumen and collagen only

Draw in the bands you would expect to see for lanes 2, 3, and 4.

4. (2 pts.) Patients with cystic fibrosis have defective chloride transport proteins.  Knowing what you know about the functions of dfferent domains of transport proteins, tell me two things that could be defective about the transporter (i.e. what are two things that normal transporter can do but a defective one might not be able to do?)

5. (4 pts.) Consider the movement of glycerol, pyruvate, ethanolamine, and alanine across the plasma membrane of a bacteria at 20° C. Both pyruvate and alanine have a charge of -1, ethanolamine has a charge of +1 and glycerol is uncharged.
Assume that the membrane potential is -95 mV and that the concentration of each solute is 0.1 mM on the outside of the cell and 2.0 mM on the inside of the cell.

Calculate the DG for inward transport of each of the compounds.

a. pyruvate ________________________

b. ethanolamiine ____________________

c. alanine _________________________

d. glycerol ________________________

6. (4 pts.) On the back of this paper, make a rough sketch of the pathway a protein would take from the ER to the outside of the cell.  Label important structures.

7. (2 pts.)  When programmed cell death occurs, the chromosomal DNA is broken (digested) up into small pieces.  Using what you know about apoptosis (programmed cell death), BRIEFLY explain how the DNA is probably broken up.