Membranes

1. Assume you are given a culture of _E. coli_ bacteria that have been growing at 25°C. You incubate the culture at 37°C. What change will the bacteria make in their plasma membranes?
a. Increase saturated fatty acids
b. Decrease steroids
c. Decrease length of fatty acid chains
d. Increase glycolipids
e. None of the above

2. You have a preparation of ghosts and need to collect only the right-side out ghosts You decide you can trap the ride-side out ghosts in an affinity column packed with:
a. SDS
b. A carbohydrate-binding molecule
c. A protein-binding antibody
d. A serine-binding molecule
e. None of the above

3. You stain membrane proteins with a fluorescent-labeled antibody and notice the membrane is evenly stained. After a few hours, all of the fluorescence is at one end of a cell. You can conclude that:
a. Lipids flip-flop in the membrane
b. Proteins move laterally in the membrane
c. The fluorescent dye was bleached
d. Proteins act as transporters
e. All of the above

4. The antibiotic amphotericin B forms channels in membranes by complexing the cholesterol. Which of the following would be killed by amphotericin B?
a. Plant cells
b. Animal cells
c. Bacterial cells
d. All of the above
e. None of the above

5. Compared to active transport, the amount of energy required for facilitated diffusion is:
a. Greater
b. Lesser
c. Equal
d. Depends on the substrate
e. Can't tell

6. Compared to active transport, the need for a transporter protein by facilitated diffusion is:
a. . Greater
b. Lesser
c. Equal
d. Depends on the substrate
e. Can't tell

7. Some bacteria are killed by detergents. In the presence of a detergent:
a. Cell contents would leak out
b. The cell membrane would become rigid
c. Water would leave the cell causing plasmolysis
d. Cell membranes would not be made correctly
e. None of the above

8. Which of the following is not true?
a. Phospholipids have hydrophilic and hydrophobic regions
b. Proteins form continuous layers in the plasma membrane
c. Membrane ports consist of transmembrane proteins
d. Animal cells without cholesterol will lyse
e. Glycolipids are used in cell recognition

9. The bumps that are visible in freeze-fracture membrane preparations for electron microscopy are:
a. Carbohydrates
b. Cholesterol molecules
c. Extrinsic proteins
d. Integral proteins
e. Phospholipids

10. Plant guard cells have a high [Cl-] than outside environments. The most likely explanation for this is:
a. Water leaves the cell by osmosis
b. Cl- is diffusing through transmembrane channels
c. Cl- diffusion is aided by a mobile carrier
d. An active transport symport transports Cl-/H+
e. None of the above

11. The transporter protein that brings a glucose and a proton into a cell is a(n):
a. Antiport
b. Symport
c. Uniport
d. Pore
e. None of the above

12. The transporter protein that brings Hg+ into a bacterial cell to detoxify the mercury is a(n):
a. Antiport
b. Symport
c. Uniport
d. Pore
e. Can't tell

13. Which of the following pairs is not correctly matched?
a. Porin-ionophore
b. Plasmodesmata-gap junction
c. Plant cell wall-bacterial cell wall
d. Tight junction-middle lamella
e. None of the above

14. The poisonous heavy metal arsenate (3+) enters cells through an ionophore for:
a. Hydrogen (1+)
b. Chloride (1-)
c. Magnesium (2+)
d. Phosphate (3+)
e. Nitrogen (3-)

15. Insulin is produced by the pancreas in response to increasing the glucose concentration of the blood. What is the most likely action of insulin?
a. Increases glucose transport proteins
b. Decreases active transport
c. Increases osmosis
d. Decreases group translocation
e. All of the above