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

Question 1

Based on your knowledge of the chemistry of the cell membrane, which of the following compounds would you couple with a new drug in order to achieve better uptake by cells?

A)carbohydrates
B)polar amino acids
C)lipids
D)any hydrophilic substance
E)several mannose- 6- phosphate monomers

Answer 1

C

Question 2

You are experimenting with a variety of lipids to determine their efficacy for use as drug delivery system liposomes. What is one feature of the individual lipid that would best ensure the use of a lipid for this purpose?

A)It must have be composed entirely of unsaturated fatty acids.
B)It should be exclusively hydrophobic.
C)It should be exclusively hydrophilic.
D)It must have a structure similar to cholesterol.
E)It should be amphipathic.

Answer 2

E

Question 3

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

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

Answer 3

B

Question 4

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

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

Question 5

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?

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 6

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

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

Question 7

With regard to the semipermeable nature of the plasma membrane, which of the following would readily cross without the aid of a transport protein?

A)glucose
B)calcium ions
C)amino acids
D)water
E)DNA

Question 8

The most common number of carbons in fatty acid hydrocarbon chains of membrane phospholipids is

A)19.
B)24.
C)16.
D)10.
E)7.

Question 9

A means of detecting the presence of specific carbohydrate moieties on glycoproteins is

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

Question 10

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

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

Question 11

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

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 12

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

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

Question 13

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

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

Question 14

Where would you expect to find an organism possessing a cell membrane with the following composition: large proportions of cholesterol and a predominance of unsaturated fatty acids?

A)equatorial regions
B)frozen wastelands
C)upper levels of an aquatic environment
D)temperate regions
E)tropical regions

Question 15

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

A)equal amounts of saturated and unsaturated fatty acids, as long as the chain was close to 12 carbons in length.
B)largely unsaturated fatty acids.
C)largely saturated fatty acids.
D)polar fatty acids.
E)none of the above

Question 16

Cholesterol

A)intercalates between the fatty acid chain within the bilayer.
B)destabilizes the cell membrane.
C)increases permeability for small cations.
D)is found only in plants.
E)is found in abundance in prokaryotic cell membranes.

Question 17

Which is NOT a model for membrane structure?

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 18

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

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 19

Which of the following is NOT a function of membranes?

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

Question 20

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

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

Question 21

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?

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

Question 22

Of the following lipids, which is found in approximately equal amounts in both the outer and inner portions of the lipid bilayer?

A)phophatidylethanolamine
B)phophatidylinositol
C)phosphatidylserine
D)glycolipid
E)cholesterol

Question 23

Hopanoids

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

Question 24

The technique that allows various proteins to be differentiated based on size, once the proteins have been denatured, is

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

Question 25

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

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

Question 26

Most unsaturated fatty acids are in the configuration, but some are in the
configuration, making their shape more like that of saturated fatty acids.

Question 27

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

Question 28

The scientist(s)who developed the "sandwich" model of the cell membrane is (are)

A)Davson and Danielli.
B)Gorter and Grendel.
C)Langmuir.
D)Robertson.
E)Overton.

Question 29

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

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

Question 30

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

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

Question 31

Localized regions of membrane lipids that contain proteins involved in cell signaling are known as

A)islands of hydropathy.
B)hopanoids.
C)lipid rafts.
D)membrane leaflets.
E)homeoviscous adaptation.

Question 32

In E. coli the enzyme responsible for creating unsaturated bonds from saturated ones in the fatty acids of the cell membrane is .

Question 33

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

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

Question 34

is a sterol associated with fungal cell membranes.

Question 35

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

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