Quiz 11.2: Membrane Proteins

How thick is the plasma membrane?

50 atoms

Treatment of this membrane with phospholipase C would release which protein or proteins from the bilayer? https://s3.amazonaws.com/RM_Images/20160122194232670_raw.jpg

B

Which statement about phospholipids and detergents is NOT true?

Phospholipids are amphipathic, whereas detergents are hydrophobic.

In a patch of animal cell membrane about 10 µm in area, which will be true?

There will be more lipids than proteins.

Multipass transmembrane proteins can form pores across the lipid bilayer. The structure of one such channel is shown in the diagram. In this figure, the areas shown in red represent: https://s3.amazonaws.com/RM_Images/20160117001221000_raw.jpg

the hydrophilic side chains of the transmembrane α helices.

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

the outside of the membrane-spanning helix.

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

Coating proteins with carbohydrates

A functionally specialized region of a cell membrane, typically characterized by the presence of specific proteins, is called a:

membrane domain

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

External (noncytosolic) side

Human red blood cells contain no internal membranes other than the nuclear membrane.

False

Which of the following is NOT a function of plasma membrane proteins?

Generate the energy required for lipids to diffuse through the membrane

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

(D) All of the above

Which of these membrane-associated protein structures has never been found in a cell membrane? https://s3.amazonaws.com/RM_Images/20160117001214739_raw.jpg

5

In a typical animal cell, approximately how much of the mass of the plasma membrane is constituted by proteins?

50%

Which is NOT an integral membrane protein?

A protein attached to the membrane by noncovalent interactions with other membrane proteins

Treatment of this membrane with a detergent like sodium dodecyl sulfate (SDS) would release which protein or proteins from the bilayer? https://s3.amazonaws.com/RM_Images/20160117001217723_raw.jpg

All of the proteins

To study the structure of a particular membrane protein, the target protein is usually removed from the membrane and separated from other membrane proteins. Shown here are three different proteins associated with the cell membrane. Treatment of this membrane with high salt would release which protein or proteins from the bilayer? https://s3.amazonaws.com/RM_Images/20160117001216210_raw.jpg

C

The movement of an individual protein in a cell membrane can be followed using a technique called single-particle tracking. In the diagram of the red blood cell cortex shown in Figure 1, actin proteins would show which of the three types of movement in Figure 2? https://s3.amazonaws.com/RM_Images/20160117001225232_raw.jpg

C

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

Hydrophobic

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

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

Treating this membrane with a lectin would release which protein or proteins from the bilayer? https://s3.amazonaws.com/RM_Images/20160117001219226_raw.jpg

None of the proteins

Fluorescence recovery after photobleaching (FRAP) is used to monitor the movement of fluorescently labeled molecules within the plane of a cell membrane. The molecules labeled are often proteins, but can also be lipids. How would the curve that represents FRAP for labeled proteins compare to the curve representing labeled lipids?

The FRAP curve for lipids would show very rapid recovery to initial levels of fluorescence.

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

cell cortex