Lehninger Principles of Biochemistry 6th Edition By David L. Nelson – Test Bank

Chapter 11 Biological Membranes and Transport

Multiple Choice Questions

1. The composition and architecture of membranes
Page: 386 Difficulty: 2 Ans: C
Which one of the following statements about membranes is true?

A) Most plasma membranes contain more than 70% proteins.
B) Sterol lipids are common in bacterial plasma membranes.
C) Sterol lipids are common in human cell plasma membranes.
D) Sterol lipids are common in plant cell plasma membranes.
E) The plasma membranes of all cell types within a particular organism have basically the same lipid and protein composition.

2. The composition and architecture of membranes
Page: 386 Difficulty: 3 Ans: C
The inner (plasma) membrane of E. coli is about 75% lipid and 25% protein by weight. How many molecules of membrane lipid are there for each molecule of protein? (Assume that the average protein is Mr 50,000 and the average lipid is 750.)

A) 1
B) 50
C) 200
D) 10,000
E) 50,000

3. The composition and architecture of membranes
Pages: 386–388 Difficulty: 2 Ans: A
Which of these statements about the composition of biological membranes is false?

A) In a given eukaryotic cell type (e.g., a hepatocyte), all intracellular membranes have essentially the same complement of lipids and proteins.
B) The carbohydrate found in membranes is virtually all part of either glycolipids or glycoproteins.
C) The plasma membranes of the cells of vertebrate animals contain more cholesterol than the mitochondrial membranes.
D) The ratio of lipid to protein varies widely among cell types in a single organism.
E) Triacylglycerols are not commonly found in membranes.

4. The composition and architecture of membranes
Pages: 386–388 Difficulty: 1 Ans: C
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
5. The composition and architecture of membranes
Pages: 389–395 Difficulty: 1 Ans: E
Membrane proteins:

A) are 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.

6. The composition and architecture of membranes
Page: 389 Difficulty: 2 Ans: A
Peripheral membrane proteins:

A) are generally noncovalently bound to membrane lipids.
B) are usually denatured when released from membranes.
C) can be released from membranes only by treatment with detergent(s).
D) may have functional units on both sides of the membrane.
E) penetrate deeply into the lipid bilayer.

7. The composition and architecture of membranes
Page: 389 Difficulty: 2 Ans: C
An integral membrane protein can be extracted with:

A) a buffer of alkaline or acid pH.
B) a chelating agent that removes divalent cations.
C) a solution containing detergent.
D) a solution of high ionic strength.
E) hot water.

8. The composition and architecture of membranes
Pages: 390–392 Difficulty: 2 Ans: B
The shortest  helix segment in a protein that will span a membrane bilayer has about _____ amino acid residues.

A) 5
B) 20
C) 50
D) 100
E) 200

9. The composition and architecture of membranes
Page: 392 Difficulty: 2 Ans: E
A hydropathy plot is used to:

A) determine the water-solubility of a protein.
B) deduce the quaternary structure of a membrane protein.
C) determine the water content of a native protein.
D) extrapolate for the true molecular weight of a membrane protein.
E) predict whether a given protein sequence contains membrane-spanning segments.

10. The composition and architecture of membranes
Pages: 393–394 Difficulty: 3 Ans: A
Which of these statements is generally true of integral membrane proteins?

A) The secondary structure in the transmembrane region consists solely of -helices or -sheets.
B) The domains that protrude on the cytoplasmic face of the plasma membrane nearly always have covalently attached oligosaccharides.
C) They are unusually susceptible to degradation by trypsin.
D) They can be removed from the membrane with high salt or mild denaturing agents.
E) They undergo constant rotational motion that moves a given domain from the outer face of a membrane to the inner face and then back to the outer.