5 Lecture Review Questions
1. Phospholipids spontaneously form bilayer structures, but oils form small droplets. Why do oils not form
bilayers?
a. Oils are not as hydrophobic as phospholipids.
b. The fatty acids in oils preclude bilayer formation.
c. Oils are energy reserves of cells.
d. Oils do not have the polar head group that phospholipids have.
e. Oils and water do not mix.
2. Which of the following statements about membrane proteins is false?
a. Hydrophilic regions of integral membrane proteins are in contact with the interior of the bilayer.
b. Peripheral membrane proteins may be associated with the phospholipid head groups.
c. Integral membrane proteins can move in the plane of the membrane.
d. Some membrane proteins may have oligosaccharides attached to them.
e. None of the above
3. A comparison of the properties of the plasma membrane to those of the membrane of lysosomes would
reveal that
a. only the plasma membrane has a lipid bilayer.
b. the two membranes contain the same proteins.
c. the two membranes have the same lipids.
d. all of the proteins in the two membranes are extrinsic to the membrane.
e. the two membranes have different proteins and lipids.
4. In addition to the bilayer lipids and proteins, membranes may contain _______ in the form of _______
and _______.
a. nucleic acids; DNA; RNA
b. carbohydrates; cellulose; starch
c. triglycerides; fats; oils
d. carbohydrates; glycoproteins; glycolipids
e. nucleotides; ATP; GTP
5. Which of the following molecules do you think would diffuse across a phospholipid bilayer fastest,
assuming that there are no proteins associated with the bilayer.
a. H2O
b. NH4+
c. CH3COO
d. NH3
e. Na+
6. What would happen if a suspension of red blood cells in an isotonic NaCl solution was suddenly diluted
with pure water by a factor of ten?
a. Nothing
b. The cells would lose water and shrink.
c. The cells would swell and lyse (burst).
d. The cells would take up water, but the cell wall would prevent bursting.
e. The cells would pump water out of the cell.
7. Osmosis is
a. the diffusion of water across membranes.
b. the active transport of water across membranes.
c. unidirectional diffusion of water across membranes.
d. unaffected by solute concentrations inside cells.
e. a process that requires energy.
8. In facilitated diffusion,
a. molecules may be transported against their concentration gradient.
b. specific integral membrane proteins mediate transport.
c. the rate of transport is independent of the concentration of the molecule transported.
d. ATP is used.
e. endocytosis is involved.
9. The specificity of ion channels for the ions they transport is
a. a result of gating of the channel.
b. independent of the size of the ion.
c. a result of the characteristics of the channel protein.
d. a result of the carbohydrates attached to the channel protein.
e. dependent only on the of charge the ion.
10. Secondary active transport resembles transport by ion channels in that
a. both types of transport can involve the movement of Na+ across the plasma membrane.
b. both types of transport are indirectly linked to the hydrolysis of ATP.
c. both can transport molecules against a concentration/electrical gradient.
d. the same membrane proteins are used for both types of transport.
e. both types of transport resemble facilitated diffusion.
11. A voltage difference is maintained across the plasma membrane. This voltage difference
a. is positive on the inside of the cell relative to the outside.
b. does not require energy to generate and maintain.
c. arises because the sodium-potassium pump pumps 2 Na+ in and 3 K+ out during one catalytic cycle.
d. arises because the sodium-potassium pump pumps 2 K+ in and 3 Na+ out during one catalytic
cycle.
e. arises from secondary active transport.
12. Receptor-mediated endocytosis
a. is non-specific.
b. allows small molecules to enter cells.
c. involves the formation of clathrin-coated vesicles.
d. directly involves the Golgi apparatus.
e. is another name for phagocytosis.
13. Which statement about ion channels is not true?
a. They form pores in the membrane.
b. They are proteins.
c. All ions pass through the same type of channel.
d. Movement through them is from regions of high concentration to regions of low concentration.
e. Movement through them is by simple diffusion.
14. Facilitated diffusion and active transport both
a. require ATP.
b. require the use of proteins as carriers or channels.
c. carry solutes in only one direction.
d. increase without limit as the concentration gradient increases.
e. depend on the solubility of the solute in lipids.
15. Which statement about membrane phospholipids is not true?
a. They associate to form bilayers.
b. They have hydrophobic tails.
c. They have hydrophilic heads.
d. They give the membrane fluidity.
e. They flip-flop readily from one side of the membrane to the other.
16. When a hormone molecule binds to a specific protein on the plasma membrane, the protein it binds to is
called a
a. ligand.
b. clathrin.
c. receptor protein.
d. hydrophobic protein.
e. cell adhesion molecule.
16. FRAP can be used to study the mobility of a protein within the plasma membrane.
A) PCR is short for polymerase chain reaction. What is FRAP short for?
Fluorescence recovery after photobleaching
B) What does it mean when you say that a fluorescent protein has been bleached?
The fluorescent moiety has been destroyed.
C) Results of a FRAP experiment are shown below. The control condition is a GFP tagged protein that is
known to move freely within the membrane. Fill in the results you would expect for a protein that is
anchored to the cytoskeleton.
Control
Samples
Bleach
Relative
Fluorescence
Bleach
Relative
Fluorescence
Time
Time