Ch 11 smartworks test 2

Which of the following would be most likely to disrupt lipid bilayer formation? Choose one: A. addition of a phosphate to the end of the lipid tail B. addition of a methyl group to the end of the lipid tail C. addition of a hydroxyl group to the head group of the lipid D. addition of cholesterol to the membrane

A. addition of a phosphate to the end of the lipid tail

A cell membrane made up primarily of lipids with which characteristics would be the least fluid (i.e., most stiff)? Choose one: A. long, saturated fatty acid tails B. long, unsaturated fatty acid tails C. short, unsaturated fatty acid tails D. short, saturated fatty acid tails

A. long, saturated fatty acid tails

Which is a mechanism for restricting the movement of proteins in the plasma membrane? Choose one or more: A. tethering proteins to the extracellular matrix B. forming a covalent linkage with membrane lipids C. tethering proteins to the cell cortex D. using barriers such as tight junctions E. tethering proteins to the surface of another cell F. coating proteins with carbohydrates

A. tethering proteins to the extracellular matrix C. tethering proteins to the cell cortex D. using barriers such as tight junctions E. tethering proteins to the surface of another cell

Which type of movement is the least common for lipids in a bilayer? Choose one: A. flexion B. flip-flop C. rotation D. lateral diffusion

B. flip-flop

Which of these macromolecules is NOT commonly found in the plasma membrane? Choose one: A. fatty acids B. proteins C. carbohydrates D. nucleic acids

D. nucleic acids

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

It tends to make the lipid bilayer less fluid.

Which term correctly describes the entire phospholipid molecule? Choose one: amphipathic hydropathic hydrophobic apathetic hydrophilic

amphipathic

Proteins that are associated with the membrane by noncovalent interactions with other membrane proteins are called ___________ proteins. Choose one: integral membrane peripheral membrane monolayer-associated lipid-linked

peripheral membrane

Which portion of a membrane phospholipid faces the outside of the membrane? Choose one: none, because phospholipids are confined to the interior of the membrane fatty acids head tail amphipathic portion

head

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? Choose one: hydrophobic polar amphipathic charged hydrophilic

hydrophobic

Which characteristic describes the tails of phospholipids? Choose one: hydrophobic stiff coated with sugars amphipathic hydrophilic

hydrophobic

Which is the most abundant phospholipid in animal cell membranes? Choose one: cholesterol glycolipid phosphatidylinositol triacylglycerol phosphatidylcholine

phosphatidylcholine

Which of the following would produce the most fluid lipid bilayer? Choose one: A. phospholipids with tails of 20 carbon atoms and two double bonds B. large amounts of cholesterol C. phospholipids with fully saturated tails of 20 carbon atoms D. phospholipids with fully saturated tails of 18 carbon atoms E. phospholipids with tails of 18 carbon atoms and two double bonds

phospholipids with tails of 18 carbon atoms and two double bonds

If the backbone of a polypeptide is hydrophilic, how can a transmembrane alpha helix span the hydrophobic portion of the lipid bilayer? Choose one: A. because the hydrophilic backbone makes a hole in the membrane B. because many transmembrane alpha helices must come together in a way that neutralizes the hydrophilic backbone C. because amino acid side chains in a transmembrane helix are hydrophobic and interact with the hydrophobic interior of the bilayer D. because the membrane bends in such a way that the polar heads of the lipids contact the transmembrane helix

C. because amino acid side chains in a transmembrane helix are hydrophobic and interact with the hydrophobic interior of the bilayer

Imagine you collected bacteria from the sediment in a frozen lake in Minnesota in January and compared the membranes to membranes from bacteria collected from a lake in Texas in June. Consider how the membranes would likely differ. The membranes in bacteria from the Minnesota lake would most likely have which of the following? Choose one: A. phospholipids with more negatively charged phosphate groups than membranes in Texas bacteria B. fewer lipid tails with cis double bonds than membranes in Texas bacteria C. more unsaturated lipid tails than membranes in Texas bacteria D. more saturated lipid tails than membranes in Texas bacteria

C. more unsaturated lipid tails than membranes in Texas bacteria

If a phospholipid is located in the outer layer of the bilayer in a vesicle, where will it end up when the vesicle fuses with the plasma membrane? Choose one: A. randomly on one side or another B. the extracellular face the bilayer C. the cytosolic face of the bilayer D. Vesicles cannot fuse with the plasma membrane.

C. the cytosolic face of the bilayer

What effect do double bonds have on phospholipid hydrocarbon tails and on the fluidity of the membrane? Choose one: Double bonds increase the ability of hydrocarbon tails to pack together into a rigid mass, which makes the bilayer less fluid. Double bonds decrease the ability of hydrocarbon tails to pack together, which makes the bilayer more fluid. Double bonds increase the ability of hydrocarbon tails to pack together into a rigid mass, which makes the bilayer more fluid. Double bonds decrease the ability of hydrocarbon tails to pack together into a rigid mass, which makes the bilayer less fluid. Double bonds have little effect on membrane fluidity.

Double bonds decrease the ability of hydrocarbon tails to pack together, which makes the bilayer more fluid.

In 1925, scientists exploring how lipids are arranged within cell membranes performed a key experiment using red blood cells. Using benzene, they extracted the lipids from a purified sample of red blood cells. Because these cells have no nucleus and no internal membranes, any lipids they obtained were guaranteed to come from the plasma membrane alone.The extracted lipids were floated on the surface of a trough filled with water, where they formed a thin film. Using a movable barrier, the researchers then pushed the lipids together until the lipids formed a continuous sheet only one molecule thick.The researchers then made an observation that led them to conclude that the plasma membrane is a lipid bilayer.Which of the following would have allowed the scientists to come to this conclusion?Choose one: When pushed together, the extracted lipids dissolved in water. The extracted lipids covered half the surface area of the intact red blood cells. The extracted lipids covered twice the surface area of the intact red blood cells. The extracted lipids covered the same surface area as the intact red blood cells.

The extracted lipids covered twice the surface area of the intact red blood cells.

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

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

In a patch of animal cell membrane about 10 μm in area, which will be true?Choose one: There will be more proteins than lipids. 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. There will be more carbohydrates than lipids. There will be about an equal number of proteins and lipids. There will be more lipids than proteins.

There will be more lipids than proteins.

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: by boosting the activity of a flippase in the plasma membrane by inactivating both a flippase and a scramblase in the plasma membrane by activating a scramblase and inactivating a flippase in the plasma membrane by inverting the existing plasma membrane by inactivating a scramblase in the plasma membrane

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

Which of the following can be a component of cell membranes? Choose one or more: cholesterol protein lipid sugar DNA

cholesterol protein lipid sugar

Organisms that live in cold climates adapt to low temperatures by doing which of the following? Choose one: increasing the amounts of unsaturated fatty acids in their membranes to help keep their membranes fluid increasing the amounts of saturated fatty acids in their membranes to help keep their membranes fluid increasing the amounts of unsaturated fatty acids in their membranes to help decrease the fluidity of their membranes increasing the amounts of saturated fatty acids in their membranes to help decrease the fluidity of their membranes decreasing the amounts of unsaturated fatty acids in their membranes to help keep their membranes fluid

increasing the amounts of unsaturated fatty acids in their membranes to help keep their membranes fluid

A less permeable membrane is likely to have Choose one: more cholesterol. less cholesterol. many unsaturated fatty acids. shorter fatty acid tails.

more cholesterol.

When grown at higher temperatures, bacteria and yeast maintain an optimal membrane fluidity by doing which of the following? Choose one: producing membrane lipids with tails that are shorter and contain fewer double bonds adding cholesterol to their membranes producing membrane lipids with tails that are shorter and contain more double bonds producing membrane lipids with tails that are longer and contain fewer double bonds producing membrane lipids with tails that are longer and contain more double bonds

producing membrane lipids with tails that are longer and contain fewer double bonds

What type of protein moves randomly selected phospholipids from one monolayer of a lipid bilayer to the other? Choose one: phospholipase flippase scramblase none; such movement occurs spontaneously and relatively quickly none; phospholipids cannot move from one monolayer to another

scramblase

When a vesicle fuses with the plasma membrane, which way will the monolayer that was exposed to the interior of the vesicle face? Choose one: the endomembrane system The direction the monolayer will face will be established randomly. It depends on where, along the plasma membrane, the vesicle fuses. the cell exterior the cell cytoplasm

the cell exterior

In eukaryotic cells, phospholipids are synthesized by enzymes bound to which of the following? Choose one: both monolayers of the endoplasmic reticulum the cytosolic face of the endoplasmic reticulum the inside of the endoplasmic reticulum the cytosolic face of the Golgi apparatus the cytosolic face of the plasma membrane

the cytosolic face of the endoplasmic reticulum

On what side of the plasma membrane are the carbohydrate chains of glycoproteins, proteoglycans, and glycolipids located? Choose one: the cytosolic side both sides the extracellular side the underside the inside

the extracellular side

All of the carbohydrates in the plasma membrane face the cell exterior. Which direction do the carbohydrates on internal cell membranes face? Choose one: the cell exterior the lumen of the vesicle or organelle the plasma membrane the glycocalyx the cytosol

the lumen of the vesicle or organelle

In the α helices of transmembrane proteins, the hydrophobic side chains face which direction? Choose one: the external or lumenal side of the membrane the outside of the membrane-spanning helix the cytosolic side of the membrane the inside of the membrane-spanning helix

the outside of the membrane-spanning helix

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

within the plane of their own monolayer