Chapter 11

Question 1

Which is NOT found in a cell membrane?
A: Lipid
B: DNA
C: Protein
D: Cholesterol

Answer 1

B: DNA

Question 2

The cell membrane is NOT involved in:

Answer 2

DNA replication

Question 3

The tails of phospholipids are:

Answer 3

hydrophobic

Question 4

The entire phospholipid molecule is:

Answer 4

amphipathic

Question 5

Which parts of the phospholipid face the outside of the membrane?

Answer 5

The head

Question 6

Why do lipids form bilayers in water?

Answer 6

The hydrophilic head is attracted to water while the hydrophobic tail shuns water.

Question 7

In a lipid bilayer, which behaves like a two-dimensional fluid, lipids rapidly diffuse:

Answer 7

within the plane of one monolayer in the bilayer.

Question 8

In one second, a lipid in an artificial bilayer may diffuse as far as what distance?

Answer 8

2 microns (the length of a large bacterial cell)

Question 9

Phospholipids with which of the following hydrocarbon tails will produce the most fluid bilayer?

Answer 9

Tails with 18 carbon atoms and two double bonds

Question 10

Margarine is made from vegetable oils in which the hydrocarbon tails have had what treatment?

Answer 10

The removal of double bonds (i.e., changing them to single bonds and adding hydrogen atoms)

Question 11

Double bonds in hydrocarbon tails have what effect on the rigidity of fats and phospholipid bilayers?

Answer 11

Double bonds decrease the ability of hydrocarbon tails to

pack together into a rigid mass.

Question 12

How does cholesterol in animal cell membranes affect the fluidity of the bilayer?

Answer 12

Cholesterol tends to stiffen the bilayer.

Question 13

In eukaryotic cells, new phospholipids are manufactured by enzymes bound to which part of the endoplasmic reticulum membrane?

Answer 13

The monolayer that faces the cytosol

Question 14

What type of enzyme moves phospholipids from one monolayer to the other in a biological membrane?

Answer 14

Flippase

Question 15

When a vesicle fuses with the plasma membrane, the monolayer that was facing the inside of the vesicle will face:

Answer 15

outside the cell

Question 16

How much of the mass of the plasma membranes is constituted by proteins?

Answer 16

50%

Question 17

Q: Which of the following is NOT a function of membrane proteins?

Answer 17

Generate the energy required for lipids to diffuse through

the membrane

Question 18

Which is NOT an integral membrane protein?
A: A transmembrane protein that spans the lipid bilayer
B: A monolayer associated protein tucked into the inner leaflet of the lipid bilayer
C: A protein attached to the membrane by non-covalent
interactions with other membrane proteins
D: A lipid-linked protein anchored to the outer leaflet of the membrane

Answer 18

C

Question 19

In the /alpha helices of transmembrane proteins, the hydrophobic side chains are facing:

Answer 19

the outside of the membrane-spanning helix.

Question 20

Porin proteins—which form large, water-filled pores in mitochondrial and bacterial membranes—fold into /beta barrel structures. The amino acids that face the outside of the barrel have what kind of side chains?

Answer 20

Hydrophobic

Question 21

Which statement about phospholipids and detergents is NOT true?
A: Phospholipids have two hydrocarbon tails, whereas detergents have just one.
B: Phospholipids are amphipathic, whereas detergents are hydrophobic.
C: Phospholipids form bilayers, whereas detergents tend to form micelles.

Answer 21

B

Question 22

Bacteriorhodopsin is a membrane transport protein that uses sunlight to do what?

Answer 22

Pump H+ out of the cell and generate a H+ gradient across the plasma membrane

Question 23

The shape of a cell and the mechanical properties of its plasma membrane are determined by a meshwork of fibrous proteins called:

Answer 23

cell cortex

Question 24

Which is not a mechanism for restricting the movement of proteins in the membrane?

Answer 24

Coating proteins with carbohydrates

Question 25

On what side of the membrane are the carbohydrate chains of glycoproteins, proteoglycans, and glycolipids located?

Answer 25

External (noncytosolic) side

Question 26

What do carbohydrates attached to cell-surface proteins and lipids provide a cell?
A: Protection from mechanical and chemical damage
B: A slimy coat that prevents cells from sticking to one another
C: A distinctive identity in cell-cell recognition
D: All of the above

Answer 26

All of the above