Chapter 11 Test

Membrane asymmetry is manifested in several ways. Which of the following are correct? Select all that apply. A. Golgi based Flippases act on specific phospholipids to preferentially move some into the cytosolic layer of a bilayer. B. A membrane associated proteoglycan will have more sugar groups then a glycoprotein. C. An integral membrane protein is likely to have a symmetric distribution of sugar groups. D. Spectrin molecules are preferentially found outside of the cell where they help maintain cell shape. E. Different proteins are preferentially associated with only the inside or outside of a cell membrane by covalent linkage to integral membrane proteins. F. Sugar groups are preferentially found on the extracellular side of a membrane.

A, B, C and F are all correct.

What function is served by the carbohydrates attached to cell-surface proteins? Choose one or more: A. establish a distinctive identity for cell-cell recognition B. allow cells to establish and maintain their shape C. promote cell-cell adhesion D. protect the cell from mechanical and chemical damage E. lubricate cells to keep them from sticking together

A, C, D and E are all correct.

In a patch of animal cell membrane about 10 μm in area, which will be true? Choose one: A. There will be about an equal number of proteins and lipids. B. There will be more lipids than proteins. C. Because the lipid bilayer acts as a two-dimensional fluid, there is no way to predict the relative numbers of proteins and lipids in any patch of cell membrane. D. There will be more carbohydrates than lipids. E. There will be more proteins than lipids.

B. There will be more lipids than proteins.

In a lipid bilayer, where do lipids rapidly diffuse? Choose one: A. not at all, because they remain in place within the bilayer B. within the plane of their own monolayer C. in and out of the bilayer D. within the plane of one monolayer and back and forth between the monolayers E. back and forth from one monolayer to the other in the bilayer

B. within the plane of their own monolayer

How does the inclusion of cholesterol affect animal cell membranes? Choose one: A. It tends to make the lipid bilayer more fluid. B.It makes the lipid bilayer wider. C. It tends to make the lipid bilayer less fluid. D. It makes the lipid bilayer more permeable. E. It has little effect on the properties of the lipid bilayer.

C. It tends to make the lipid bilayer less fluid.

Why do phospholipids form bilayers in water?Choose one: A. The hydrophobic head shuns water, while the hydrophilic tail is attracted to water. B. The hydrophobic tail is attracted to water, while the hydrophilic head shuns water. C. The hydrophilic head is attracted to water, while the hydrophobic tail shuns water. D. The hydrophobic head is attracted to water, while the hydrophilic tail shuns water. E. The hydrophilic head is insoluble in water.

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

Which of the following is a common transmembrane protein structure that can traverse the membrane to form a pore or channel by alternating hydrophobic and hydrophilic amino acids? Choose one: A. single-pass alpha helix B. beta sheet C. multipass alpha helix D. beta barrel

D. beta barrel

Animals exploit the phospholipid asymmetry of their plasma membrane to distinguish between live cells and dead ones. When animal cells undergo a form of programmed cell death called apoptosis, phosphatidylserine—a phospholipid that is normally confined to the cytosolic monolayer of the plasma membrane—rapidly translocates to the extracellular, outer monolayer. The presence of phosphatidylserine on the cell surface serves as a signal that helps direct the rapid removal of the dead cell.How might a cell actively engineer this phospholipid redistribution? Choose one: A. by inactivating a scramblase in the plasma membrane B. by inverting the existing plasma membrane C. by boosting the activity of a flippase in the plasma membrane D. by inactivating both a flippase and a scramblase in the plasma membrane E. by activating a scramblase and inactivating a flippase in the plasma membrane

E. by activating a scramblase and inactivating a flippase in the plasma membrane