Membrane Structure

Question 1

Membrane lipids are amphipathic

A) have hydrophilic heads, Hydrophobic tails
B) Hydrophobic heads, Hydrophilic tails
C) Nither

Answer 1

A

Question 2

In phospolipids a hydrophilic head is linked to the rest of the lipid through
A) Nonpolar group
B) Phosphate Group
C) Hydroxl Group
D) Hydrophobic tails

Answer 2

B

Question 3

The most common phospolipid is
A) Phosphatidylcholine
B)Phoshatidylserine
C)Cholesterol
D) Glycogen

Answer 3

A

Question 4

Which group cannot form bonds with water molecules
A) Phoshatidylserine
B) Glycogen
C) Triacyglycerols
D) Cholesterol

Answer 4

C

Question 5

Which groups can form noncovalent bonds with water?

A) Hydrophobic head groups
B) Hydroflaks
C) Hydrophilic head groups
D) Lipid bailyer

Answer 5

C

Question 6

The self-organizing properties of amphipathic
membrane phospholipids, in the absence of any
proteins, can produce which of the following?
A. spontaneous formation of enclosed lipid vesicles
B. spontaneous repair of tears in the membranes
C. constant movement of membrane lipid molecules
within one layer but not to the other layer of the
bilayer.
D. A and B are produced but not C.
E. A, B and C are produced.

Answer 6

E

Question 7

You LOWER the temperature of a bacterium from 30oC to
200C. How might the organism respond to maintain constant
fluidity in its plasma membrane (same at 20oC as at 300C)?
A. Increase the number of saturated fatty acid tails in its
membranes
B. Increase the number of unsaturated fatty acid tails in its
membrane
C. Increase the length of the fatty acid tails in its membrane
D. A and C are both correct.
E. B and C are both correct.

Answer 7

B

Question 8

Integral membrane proteins include
A) Transmembranes
B) Lipid-linked
C) Protein attached
D) Monolayer- associated
E) A and D
F) B and A

Answer 8

E

Question 9

Which one of the following would most likely be
extracted from a membrane by increasing the salt
concentration in the medium surrounding the membrane?
A. a peripheral membrane protein
B. an integral membrane protein spanning the membrane
with two alpha helices
C. an integral membrane proteins embedded in only one of
the two bilayers
D. an integral membrane protein inserted into the
membrane with a lipid tail
E. a protein spanning the membrane with one alpha helix

Answer 9

A

Question 10

When the polypeptide chain crosses the membrane just once,
hydrophobic amino acids are typically exposed on the ______ of an a-helix

A) outside
B) inside
C) Both

Answer 10

A

Question 11

Why do atoms of the peptide bond form a-helices

A) they are hydrogen bonded
B) have a partial charge
C) are noncovalent
D) All of the above

Answer 11

B

Question 12

Pores which allow passage of hydrophilic molecules can be formed by
multiple a-helices arranged in a cylinder, with

A) hydrophobic side chains exposed to outside, hydrophilic exposed to inside
B) Both hydrophilic side chains exposed to outside, hydrophilic exposed to inside
C) Both hydrophobic side chains exposed to outside, hydrophobic exposed to inside
D) hydrophilic side chains exposed to outside, hydrophobic exposed to inside

Answer 12

A

Question 13

In beta sheets Large pores are formed because
A) Hydrophobic side chians on inside, Hydrophilic on inside
B) Hydrophilic side chains are on the inside, Hydrophobic on the outside.
C) Hydrophobic side chains on the inside and outside.

Answer 13

B

Question 14

Which of the following would be found in a
transmembrane protein?
A. A polypeptide that passes through the membrane once as
an alpha helix with only hydrophobic residues in the helix
B. A polypeptide that passes through the membrane multiple
times as alpha helices, with hydrophilic residues facing the
membrane and hydrophobic residues facing the inside of a
channel
C. A beta barrel sheet pore with hydrophilic residues facing
the membrane and hydrophobic residues facing the inside
of the barrel
D. A and B could both be found but not C.
E. A, B and C could all be found.

Answer 14

A

Question 15

What is the structure of detergent molecules?

Answer 15

ONE hydrophobic tail, Bigger hydrophilic heads, wedged shaped form micelles

Question 16

What would one have to do to a phospholipid
molecule to make it more like a detergent
molecule?
A. make its charged head group larger
B. make its charged head group smaller
C. eliminate one of its fatty acid tails
D. A and C would both work.
E. B and C would both work.

Answer 16

D

Question 17

What is the plasma membrane reinforced by

A) Transmembrane proteins
B) cell crotex
C)Cytosolic surface

Answer 17

B

Question 18

The extracellular face of the plasma membrane has short _____ and long _________ chains of sugars attached to many
of the proteins and lipids exposed on this side.

A) 1(in
glycoproteins), (in proteoglycans)
B)(in proteoglycans), in
glycoproteins
C) Tags, Sugar

Answer 18

A

Question 19

The extracellular face of the plasma membrane has short (in
glycoproteins) and long (in proteoglycans) chains of sugars attached to many
of the proteins and lipids exposed on this side.
a. Protect the cells from chemical and physical damage
b. Absorb water to give the outside of the cell a slimy coat
(lubrication)
c. Because of diverse sequences and linkages, they are tags which
allow particular molecules, and other types of cells, to bind
d. all of the above

Answer 19

d

Question 20

Single particle tracking of individual protein molecules
(e.g., tagged with gold particles/IgG) show

A) Some of variation
in diffusion rates and extents.
B) Lower variation
in diffusion rates and extents.
C) No variation in duffusion rates and extents
D) a lot of variation
in diffusion rates and extents.

Answer 20

D

Question 21

Mild detergents like triton 100x can be used to
A) Solubilize and reconstitute functional membrane proteins
B) Break proteins apart
C) Reconstitute functional membrane proteins
D) Add phospholipids

Answer 21

A

Question 22

Which of the following is NOT found in a lipid bilayer cell membrane?
A. Phosphatidylcholine
B. Cholesterol
C. triacylglycerol
D. Phosphatidylserine
E. All of the above (A, B, C and D) are found

Answer 22

C

Question 23

Which of the following is produced by the self-organizing properties of amphipathic
membrane phospholipids, in the absence of any proteins?
A. spontaneous formation of enclosed lipid vesicles from bilayers with edges exposed to water
B. spontaneous repair of tears in the membranes
C. constant movement of membrane lipid molecules within one layer of the lipid bilayer but
almost no movement of membrane lipids molecules between the two layers
D. The organization of the lipid bilayer, with hydrophilic heads pointed towards the water and
two layers of fatty acid tails on the inside
E. All of the above (A, B, C and D) are produced

Answer 23

E

Question 24

You LOWER the temperature of a bacterium from 30C to 20C. How might the organism
respond to maintain constant fluidity in its plasma membrane (same at 20C as at 30C)?
A. Increase the number of unsaturated fatty acid tails in its membrane
B. Increase the number of saturated fatty acid tails in its membrane
C. increase the length of the fatty acid tails in its membrane
D. A and C are both correct.
E. B and C are both correct.

Answer 24

A

Question 25

_______(1) selectively transfer lipids from the extracellular or lumenal side of the membrane
to the cytosolic side, and ________(2) transfer phospholipids randomly from one monolayer
of the membrane to the other.
A. Scramblases (1), flippases (2)
B. Flippases (1), scramblases (2)
C. Scramblases (1), scramblases (2)
D. Flippases (1), flippases (2)
E. Scramblases (1), vesicles (2)

Answer 25

B

Question 26

Sugar chains are typically found attached to lipids and proteins
A. On the lumenal side of the Golgi apparatus
B. On the extracellular side of the plasma membrane
C. On the cytosolic side of the plasma membrane
D. A and B are both correct.
E. B and C are both correct.

Answer 26

D

Question 27

Which of the following membrane-associated proteins would have part of its polypeptide
chain inserted into the membrane?
A. A transmembrane protein
B. A protein with a monolayer-associated alpha-helix
C. A peripheral membrane protein
D. A and B are both correct but not C.
E. B and C are both correct but not A

Answer 27

D

Question 28

hich of the following could be found in a transmembrane protein?
A. A polypeptide that passes through the membrane once as an alpha helix with only hydrophilic
residues in the helix
B. A polypeptide that passes through the membrane multiple times as alpha helices, with
hydrophobic residues facing the membrane and hydrophilic residues facing the inside of a
channel
C. A beta barrel sheet with hydrophobic residues facing the inside of the barrel and hydrophilic
residues facing the membrane
D. B and C could all be found but not A.
E. A, B and C could all be found

Answer 28

B

Question 29

Which of the following would NOT be a common orientation for a detergent molecule?
A. Its hydrophilic part facing the interior of a lipid bilayer and its hydrophobic part facing water
molecules
B. Its hydrophilic part facing water molecules and it hydrophobic part facing hydrophobic parts
of the protein.
C. Its hydrophilic part facing water and its hydrophobic parts inside a micelle with hydrophobic
parts of other detergent molecules
D. A and B are both not common.
E. B and C are both not common.

Answer 29

A

Question 30

In the experiment in which mouse cells with red-fluorescing plasma membrane proteins were
fused with human cells with green-fluorescing plasma membrane proteins, what would
happen if the temperature were lowered immediately after the cells were fused?
A. The red and green proteins would mix faster than they would have at the higher temperature.
B. The red and green proteins would mix slower than they would have at the higher temperature.
C. The red and green proteins would mix at the same rate as they would have mixed at the higher
temperature.
D. The red and green proteins would no longer fluoresce.
E. The red protein would fluoresce green and the green protein would fluoresce red

Answer 30

B