Question 1

To facilitate the regulation of membrane fluidity, E.coli has the enzyme

Accepted Answer

A)  fatty acid convertase.
B)  gangliosidase.
C)  unsaturase.
D)  desaturase.
E)  bacteriorhodopsin. D

Question 2

Temperature has a dramatic effect upon cell membranes. This influence can readily make a cell membrane more solid or more fluid in response to the temperature. This is an example of

Accepted Answer

A)  membrane flexibility.
B)  membrane asymmetry.
C)  scanning calorimetry.
D)  liquidation.
E)  phase transition. E

Question 3

Hopanoids

Accepted Answer

A)  are related to cholesterol.
B)  are a type of phospholipid.
C)  are a type of glycolipid.
D)  are found in eukaryotes only.
E)  all of the above A

Question 4

Which of the following is a sterol- like lipid associated with the cell membrane of prokaryotes?

Accepted Answer

A)  phytosterol
B)  stearate
C)  linoleate
D)  palmitate
E)  hopanoids

Question 5

Based on the composition of cell membranes, the most prominent lipids are

Accepted Answer

A)  cerebrosides.
B)  phospholipids.
C)  glycolipids.
D)  phytosterol.
E)  cholesterol.

Question 6

Cell- cell communication in plants takes place via specialized structures called

Accepted Answer

A)  plasmodesmata.
B)  cell wall pores.
C)  gap junctions.
D)  connexons.
E)  desmids.

Question 7

Which of the following is NOT a function of membranes?

Accepted Answer

A)  regulation of transport
B)  information storage
C)  define cell boundaries
D)  compartmentalization
E)  cell- cell communication

Question 8

Starting with shredded spinach leaves, you follow a procedure that allows for separation of cellular organelles. You are specifically looking for the fraction that contains the mitochondria. To identify this fraction you should test for the

Accepted Answer

A)  phospholipids unique to intracellular membranes.
B)  presence of enzymes associated with cellular respiration.
C)  phospholipids unique to the mitochondrial membrane.
D)  general presence of enzymes that fix carbon.
E)  polysaccharides that specifically surround the mitochondria.

Question 9

Which is NOT a model for membrane structure?

Accepted Answer

A)  Gorter and Grendel bilayer
B)  Watson and Crick double helix
C)  Overton lipid coat
D)  Langmuir monolayer
E)  Singer and Nicholson fluid mosaic

Question 10

The likely number of and locations of transmembrane segments of integral membrane proteins is inferred by

Accepted Answer

A)  X- ray crystallography.
B)  hydropathic analysis.
C)  affinity labeling.
D)  western blot.
E)  SDS- PAGE.

Question 11

Two cells with different cell- surface markers are fused in the presence of polyethylene glycol (PEG). The cells are then placed at 0°C. What do you expect to observe about the individual cell markers?

Accepted Answer

A)  The markers will essentially remain where they are, with little migration.
B)  The markers will be endocytosed by the fused cell and then redistributed as fused markers.
C)  Only one marker will disperse while the other remains stationary.
D)  Both sets of markers will not mix, but will migrate to opposite poles from one another.
E)  The markers will evenly disperse throughout both membranes.

Question 12

Many integral membrane proteins have not been analyzed by X- ray crystallography. However, transmembrane segments can be inferred using computer analysis of the amino acid sequence of the protein. This technique is known as

Accepted Answer

A)  SDS- PAGE.
B)  lipid analysis.
C)  hydropathic analysis.
D)  lipid rafting.
E)  homeoviscous adaptation.

Question 13

Inactivation of a fluorescent dye in a very concentrated spot on a cell so that the fluidity of membranes is visualized is called

Accepted Answer

A)  photobleaching.
B)  ferritin conjugated lectins.
C)  the freeze fracture technique.
D)  liposome formation.
E)  SDS- PAGE.

Question 14

Which of the following molecules would NOT readily cross an intact cell membrane by simple diffusion?

Accepted Answer

A)  oxygen
B)  glucose
C)  water
D)  ethanol
E)  fatty acids

Question 15

A prokaryotic organism is isolated from a glacier, where it has been observed to be thriving. Based on your knowledge of the plasma membrane, you would expect to find a predominance of

Accepted Answer

A)  equal amounts of saturated and unsaturated fatty acids, as long as the chain was close to 12 carbons in length.
B)  largely saturated fatty acids.
C)  largely unsaturated fatty acids.
D)  cell wall to define the cell, as the cell membrane would not be present.
E)  none of the above

Question 16

Which of the following disorders is the result of impaired glycosphingolipid metabolism?

Accepted Answer

A)  Tay- Sachs disease
B)  leprosy
C)  polydactyly
D)  tuberculosis
E)  glycosphingolipid anemia

Question 17

You are examining an electron micrograph of cells obtained from a new deep- sea life form. Upon closer examination, you notice that there are two dark lines separated by a lightly stained region. These results are similar to the observation of which person's or persons' investigation into membrane structure?

Accepted Answer

A)  Singer and Nicolson
B)  Gorter and Grendel
C)  Overton
D)  Unwin and Henderson
E)  Robertson

Question 18

With respect to the outer and inner faces of the lipid bilayer of the cell membrane, the composition of proteins is

Accepted Answer

A)  identical.
B)  a mirror image.
C)  highly random and varies throughout the cell.
D)  not identical, but symmetrical.
E)  asymmetrical.

Question 19

is the name given to the technique that utilizes radioactive molecules that bind to specific membrane proteins.

Accepted Answer

The answer of is the name given to the technique...

Question 20

With respect to the outer and inner faces of the lipid bilayer of the cell membrane, the composition of lipids is

Accepted Answer

A)  identical.
B)  a mirror image.
C)  highly random and varies throughout the cell.
D)  asymmetrical.
E)  not identical, but symmetrical.

Exam 7: Membranes: Their Structure, Function, and Chemistry