Question

Which of these statements about the composition of membranes is true?

A) All biological membranes contain cholesterol.

B) Free fatty acids are major components of all membranes. C) The inner and outer membranes of mitochondria have different protein compositions.

D) The lipid composition of all membranes of eukaryotic cells is essentially the same.

E) The lipid: protein ratio varies from about 1: 4 to 4: 1

Membrane proteins:

A) ere sometimes covalently attached to lipid moieties:

B) are sometimes covalently attached to carbohydrate moieties.

C) are composed of the same 20 amino acids found in soluble proteins.

D) diffuse laterally in the membrane unless they are anchored

E) have all of the properties listed above.

Which of these is a general feature of the lipid bilayer in all biological membranes?

A) Individual lipid molecules are free to diffuse laterally in the surface of the bilayer.

B) Individual lipid molecules in one face (monolayer) of the bilayer readily diffuse (flip-flop) to the other monolayer.

C) Polar, but uncharged, compounds readily diffuse across the bilayer.

D) The bilayer is stabilized by covalent bonds between neighboring phospholipid molecules.

E) The polar head groups face inward toward the inside of the bilayer.

The fluidity of a lipid bilayer will be increased by:

A) decreasing the number of unsaturated fatty acids.

C) decreasing the temperature.

B) increasing the length of the alkyl chains.

D) increasing the temperature.

E) substituting 18: 0 (stearic acid) in place of 18: 2 (linoleic acid).

Scatchard analysis can provide information on:

A) enzyme cascades.

B) enzyme mechanisms.

C) gated ion channels.

D) protein phosphorylation.

E) receptor-ligand interactions.

Which of the following is not involved in signal transduction by the b-adrenergic receptor pathway?

A) Cyclic AMP synthesis

B) GTP hydrolysis

C) GTP-binding protein

D) Protein kinase

E) All of the above are involved.

TRUE or FALSE - When a vesicle fuses with a cellular membrane, the outer leaflet of the vesicle becomes part of the outer leaflet of cell membrane and the inner leaflet of vesicle becomes part of the inner leaflet of the cell membrane.

Answer 1

Q.1

C) the inner and outer membranes of mitochondria have different protein compositions.

Q.2

E) have all the properties listed above.

Q.3

A) Individual lipid molecules are free to diffuse laterally in the surface of the bilayer.

Q.4

D) increasing the temperature.

Q.5

E) receptor- ligand interactions.

Q.6

E) All of the above are involved.

Answer 2

1. E is the correct answer

Generally, membranes are composed of approximately 75% lipids, 20% proteins, and 5% carbohydrates. The mass ratio of lipids to proteins can range anywhere from 1:4 to 4:1.

2. Option E

All of the above features for membrane proteins are correct.

3. Option A

Phospholipid molecules in synthetic bilayers are reported to rarely display migration from the monolayer on one side to that on the other. This “flip-flop,” movement occurs less frequently. In lipid molecules, on the other hand, have the capacity to readily exchange places with their neighbors (lateral diffusion) within the same monolayer.

4. Option D.

As temperature increases, the bilayer fluidity also increases. At high temperatures, the phospholipids have enough kinetic energy to resist the intermolecular forces holding the membrane together.

5. Option E

The Scatchard equation in molecular biology is used to calculate the affinity and number of binding sites of a receptor for a ligand.

6. Option E-

all of the above are involved.

7. True.

The outer leaflet of the vesicle is reported to merge with the tethered membrane, and in this way it inhibits further diffusion. The inner leaflet also fuses with the luminal side of the cell membrane.