Cell Bio Chapter 11 problem set

A phospholipid is inserted into the cytosolic side of the ER membrane. Which of the following could randomly reposition this phospholipid to the other (lumen) side of the ER membrane? A. scramblase B. flippase C. Golgi apparatus D. glycolipids

A

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? A. the cytosolic face of the bilayer B. the extracellular face the bilayer C. Vesicles cannot fuse with the plasma membrane. D. randomly on one side or another

A

In a fluorescence recovery after photobleaching (FRAP) experiment, a fluorescently tagged membrane protein, A, shows very little recovery of fluorescence ten minutes after photobleaching, while membrane protein B shows a rapid increase in fluorescence after bleaching, recovering nearly 80% of its original fluorescent signal by ten minutes. Based on this information, which of the following statements can be made? A. Protein B is diffusing in a more fluid membrane. B. Protein A has faster mobility in the membrane. C. Protein A is easily denatured. D. Proteins A and B interact with each other in a complex.

A

Plasma membrane proteins that move ions in and out of cells using active transport are called A transporters B receptors C channels D anchorS

A

Shown is a schematic diagram of a membrane phospholipid. Which segment could carry a positive charge? A B C D E

A

Which of the following is NOT a way that cells restrict the lateral movement of membrane proteins? A. reducing the temperature of the membrane B. establishing diffusion barriers in the membrane C. anchoring to internal cell components like actin or other proteins D. tethering to external cell components like the extracellular matrix or adjacent cells

A

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

A

Why do cells regulate their membrane fluidity? A. to allow membrane proteins to diffuse to where they are needed for their function B. to keep two neighboring cells from easily fusing C. so they don't freeze in cold temperatures D. so that large, charged molecules can easily pass through the membrane

A

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

A B C D

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? A. phospholipids with more negatively charged phosphate groups than membranes in Texas bacteria B. more unsaturated lipid tails than membranes in Texas bacteria C. more saturated lipid tails than membranes in Texas bacteria D. fewer lipid tails with cis double bonds than membranes in Texas bacteria

B

Shown is a schematic diagram of a membrane phospholipid. Which segment will always carry a negative charge? A B C D E

B

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

B

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

B

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

It tends to make the lipid bilayer less fluid.

________ are the most abundant molecules in the animal cell membrane, whereas ________ make up 50% of the membrane by mass. Lipids, proteins Carbohydrates, lipids Proteins, lipids Lipids, carbohydrates

Lipids, proteins

Which statements are true about the differences between phospholipids and detergents? Phospholipids are hydrophobic, whereas detergents are amphipathic. Phospholipids are amphipathic, whereas detergents are hydrophobic. Phospholipids have two hydrocarbon tails, whereas detergents have just one. Phospholipids form bilayers in water, whereas detergents tend to form micelles. Detergents are shaped like cones, whereas phospholipids are more cylindrical.

Phospholipids have two hydrocarbon tails, whereas detergents have just one. Phospholipids form bilayers in water, whereas detergents tend to form micelles. Detergents are shaped like cones, whereas phospholipids are more cylindrical.

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

There will be more lipids than proteins.

What is true of human red blood cells? They possess no internal membranes. They possess a nuclear membrane, but no other internal membranes. They possess internal membranes, but no plasma membrane. They possess no membranes.

They possess no internal membranes.

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

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

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

the lumen of the vesicle or organelle

Why must all living cells carefully regulate the fluidity of their membranes? to allow membranes, under appropriate conditions, to fuse with one another and mix their molecules. to constrain and confine the movement of proteins within the membrane bilayer to allow cells to function at a broad range of temperatures to permit membrane lipids and proteins to diffuse from their site of synthesis to other regions of the cell to ensure that membrane molecules are distributed evenly between daughter cells when a cell divides

to allow membranes, under appropriate conditions, to fuse with one another and mix their molecules to permit membrane lipids and proteins to diffuse from their site of synthesis to other regions of the cell to ensure that membrane molecules are distributed evenly between daughter cells when a cell divides

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

within the plane of their own monolayer

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 charged amphipathic polar hydrophilic

hydrophobic

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

hydrophobic

Phospholipids assemble into in a membrane using covalent bonds. hydrophobic forces. assembly proteins. enzymes.

hydrophobic forces.

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

What is a functionally specialized region of a cell membrane, typically characterized by the presence of specific proteins, called? glycocalyx carbohydrate layer sphingomyelin domain membrane domain cell cortex

membrane domain

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

more cholesterol.

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

peripheral membrane

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

phosphatidylcholine

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

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

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

the cell exterior

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

the cytosolic face of the endoplasmic reticulum

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

the extracellular side

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

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

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

A. flip-flop

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

C

A cell membrane made up primarily of lipids with which characteristics would be the least fluid (i.e., most stiff)? A. long, unsaturated fatty acid tailsB. short, saturated fatty acid tailsC. short, unsaturated fatty acid tailsD. long, saturated fatty acid tails

D

In a famous experiment, mouse cells and human cells were fused into hybrid cells and the membrane proteins of human origin and mouse origin were specifically tagged and examined. After cell fusion and incubation, what was observed by investigators? A. The mouse proteins mixed throughout the membrane of the hybrid cell, whereas the human proteins remained in half of the membrane, in their original location. B. The human proteins mixed throughout the membrane of the hybrid cell, whereas the mouse proteins remained in half of the membrane, in their original location. C. The mouse and human proteins remained separated from each other on opposite sides of the hybrid cell. D. The mouse and human proteins mixed evenly throughout the membrane of the hybrid cell.

D

What kind of lipid molecule is represented in this figure? A. triacylglycerol B. cholesterol C. glycolipid D. phospholipid

D

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

D

Where are new phospholipids made? A. Golgi apparatus B. nucleus C. mitochondria D. endoplasmic reticulum

D

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? A. beta sheet B. multipass alpha helix C. single-pass alpha helix D. beta barrel

D

What effect do double bonds have on phospholipid hydrocarbon tails and on the fluidity of the membrane? 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, 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 less 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.

Which membrane would show a more rapid recovery of fluorescence in a FRAP study? A. a membrane containing equal amounts of saturated and unsaturated fatty acids B. The saturation of fatty acids in a cell membrane does not affect the speed of fluorescence recovery in a FRAP study. C. a membrane containing a larger proportion of saturated fatty acids D. a membrane containing a large amount of cholesterol E. a membrane containing a larger proportion of unsaturated fatty acids

E

Which of the following can be a component of cell membranes? protein DNA cholesterol sugar lipid

EVERYTHING BUT DNA

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? 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. When pushed together, the extracted lipids dissolved in water. 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? The hydrophobic head shuns water, while the hydrophilic tail is attracted to water. The hydrophilic head is attracted to water, while the hydrophobic tail shuns water. The hydrophobic tail is attracted to water, while the hydrophilic head shuns water. The hydrophilic head is insoluble in water. The hydrophobic head is attracted to water, while the hydrophilic tail shuns water.

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

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

amphipathic

Which of the following is a function of proteins in the plasma membrane? generate the energy required for lipids to diffuse within the membrane allow specific ions to cross the plasma membrane, thereby controlling its electrical properties transport molecules across the membrane serve as anchors to attach the cell to the extracellular matrix transmit extracellular signals to the cell interior

allow specific ions to cross the plasma membrane, thereby controlling its electrical properties transport molecules across the membrane Serve as anchors to attach the cell to the extracellular matrix transmit extracellular signals to the cell interior

Detergent molecules are ___________ in nature and bind with membrane proteins and membrane lipids to disrupt their interactions and release the proteins from the membrane. amphipathic hydrophilic polar hydrophobic

amphipathic

The shape of a cell and the mechanical properties of its plasma membrane are determined by a meshwork of fibrous proteins called what? basal lamina tight junction lamellipodium cell cortex glycocalyx

cell cortex

The plasma membrane is involved in which activities? RNA interference cell recognition DNA replication and repair import and export of nutrients and wastes cell growth and motility cell signaling

cell recognition import and export of nutrients and wastes cell growth and motility cell signaling

What function is served by the carbohydrates attached to cell-surface proteins? establish a distinctive identity for cell-cell recognition lubricate cells to keep them from sticking together promote cell-cell adhesion allow cells to establish and maintain their shape protect the cell from mechanical and chemical damage

establish a distinctive identity for cell-cell recognition lubricate cells to keep them from sticking together promote cell-cell adhesion protect the cell from mechanical and chemical damage

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

head