Chapter 4 Practice quiz

On average, how many amino acids engaged in predominantly hydrophobic a- helices does it take to cross the hydrophobic part of the membrane?

about 20 amino acids

A transport system that moves one solute into the cell and another one out of the cell during a single cycle accompanied by the expenditure of energy through ATP hydrolysis could be called a(n) _______

active antiport

One reason why gene therapy has NOT been successful in the treatment of cystic fibrosis is that:

adenovirus did not integrate its own DNA into the target cell and had to be re-administered frequently, increasing the risk of an inflammatory response.

The fine extension of a neuron that conducts impulses away from the cell body is:

an axon.

Lipid rafts:

are thought to be patches of cholesterol and sphingolipids that tend to float within the more fluid environment of phosphoglycerides.

Membrane carbohydrates:

can be covalently linked to membrane proteins or to membrane lipids.

Aquaporins:

can be regulated by the hormone vasopressin.

An action potential is ultimately caused by:

changes in membrane permeability.

Membranes contain a wide diversity of lipids, including ________.

cholesterol, phosphoglycerides and sphingolipids

The ten alpha-helices in the transmembrane domain:

create a channel through the membrane where the ion binding and transit may occur.

Which organism provided an ideal system for the study of the nicotinic acetylcholine receptor?

electric fish

Diffusion:

eliminates a concentration gradient between two regions.

What are the building blocks of a phosphoglyceride, specifically phosphatidic acid?

glycerol + 1 phosphate group + 2 fatty acids

Saturated fatty acids:

have straight fatty acyl chains.

Movement of membrane proteins may be restricted by all of the following EXCEPT:

increased temperature.

Acetylcholine:

increases in concentration in the synaptic cleft in the presence of drugs that inhibit acetylcholinesterase.

Signal transduction:

involves the response of a cell to external stimuli, such as specific molecules or light.

An electrochemical gradient:

is determined by the concentration difference of a substance between two compartments and by the difference in charge between two compartments.

A symport:

is used to move Na+ and glucose together into the epithelial cells of the intestine.

The substance a-bungarotoxin possesses all of the characteristics EXCEPT that:

it binds to dopaminergic receptors.

The major drawback of using fluorescence recovery after photobleaching (FRAP) to follow the movements of molecules in the membranes of living cells is:

it can only be used to follow the average movements of a relatively large number of molecules over a relatively large distance.

The plasma membrane of the human erythrocyte is the MOST studied and BEST understood of all the diverse types of membrane because:

it is easily obtained by hemolysis of red blood cells.

If a red blood cell were added to a hypotonic solution,:

it would rapidly gain water and swell or burst.

It is thought by some investigators that cholesterol and sphingolipids self-assemble into microdomains within the plasma membrane that are more gelated and highly ordered than surrounding regions that contain primarily phospholipids. It is hypothesized that certain proteins tend to concentrate in these so-called ________, thereby organizing the membrane into functional compartments.

lipid rafts.

Individuals that lack glycophorin A in their red blood cell membranes:

may be protected from the protozoan that causes malaria.

Proteins that penetrate the lipid bilayer _________.

may pass entirely through the lipid bilayer and protrude from both the extracellular and cytoplasmic sides of the membrane.

The sodium-potassium pump, or Na+/K+ ATPase:

moves both Na+ ions and K+ ions across the membrane against their concentration gradients.

Where in a myelinated axon are action potentials generated?

nodes of Ranvier

The movement of water molecules down its concentration gradient and across selectively a permeable membrane is known as _________.

osmosis.

Passive transport includes _________.

osmosis. facilitated diffusion. diffusion of a substance directly across the lipid bilayer of the membrane. (All of these.)

Ankyrin and spectrin are peripheral membrane proteins that:

play a major role in determining the biconcave shape of the erythrocyte.

What word below characterizes the amino acids that are found in an α-helical segment that spans a membrane?

predominantly hydrophobic

Tetrahydrocannabinol, the active ingredient in marijuana, binds to receptors located in the ________ terminals of certain brain neurons. It lowers the likelihood that these neurons will release ________.

presynaptic, neurotransmitters

MOST functions of cell membranes are carried out by:

proteins.

Most of the functions of a cell membrane are performed by ________.

proteins.

Membrane fluidity can be increased by all of the following mechanisms EXCEPT:

raising the melting temperature of the lipid bilayer fatty acids.

Facilitated diffusion:

requires a concentration gradient.

What appears to serve as "fences" around portions of the membrane that restrict the distance an integral protein can travel?

the membrane's underlying cytoskeleton

All of the following characteristics are common to facilitated diffusion and active transport EXCEPT for ___________.

the requirement for energy.

Potassium and sodium cannot move through the cell membrane into the cell on their own because:

these ions are charged.

Integral membrane proteins are difficult to isolate in a soluble form because:

they possess hydrophobic transmembrane domains.

The temperature at which the lipids that compose the lipid bilayer convert from a liquid crystalline phase to a frozen crystalline gel in which phospholipid-fatty-acid-chain movement is greatly restricted is called the _________.

transition temperature.

The ratio of lipids to proteins in a membrane:

varies considerably depending upon the type of cell and membrane, the organism, and the function of the membrane.

Gated channels may be opened or closed by all of the following EXCEPT:

voltage clamping.

The best understood gated channel is:

voltage-gated potassium ion channels.

Under which conditions would a cell membrane be most likely to be in a liquid, crystalline state, in which an individual phospholipid can rotate around its axis or move laterally through the plane of the bilayer?

warmer temperatures around 37°C

In the cell fusion experiments of Larry Frye and Michael Edidin of Johns Hopkins University,:

(All of the choices are correct.) fluorescent dyes were covalently linked to antibodies for membrane proteins. cells from mice and from humans were fused to each other. it was shown that membrane proteins could move within the plane of the membrane. indicated that the mobility of membrane proteins was decreased at lower temperatures.

Which of these processes REQUIRES input of energy to move materials across a membrane?

Active transport that moves substances against a concentration gradient.

Which of the following statements is TRUE regarding phospholipids?

Carbohydrates found on the plasma membrane of the red blood cell:

Drugs may affect behavior by having which of these effects at the synapse?

Drugs may affect behavior by all of these mechanisms.

Which of the following statements is FALSE regarding the diffusion of substances through membranes?

Glucose passively diffuses into cells where it is used as a nutrient.

Which of the following compounds can diffuse across a phospholipid bilayer?

H2O

Which of the following is true about the cholesterol associated with membranes?

It interferes with the movements of the fatty acid tails of the phospholipids.

Which one of the following statements regarding the myelin sheath is FALSE?

It slows down propagation of nerve impulses along an axon.

Which of the following statements is true regarding the mobility of membrane components?

Lipids tend to move more rapidly than proteins within the plane of the membrane.

Which of the following statements is NOT true of the freeze-fracture replication technique?

Most of the membrane-associated particles visualized by this technique are peripheral membrane proteins

_________ can be used to trap integral proteins and drag them through the membrane with a known force, using forces generated by a focused laser beam. This yields information about the presence of membrane barriers.

Optical tweezers

Which of the following statements about membrane proteins is FALSE?

Peripheral proteins provide about 60% of all current drug targets.

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

Providing a nonselective permeable barrier.

How do cells transport small, nonpolar, hydrophobic molecules, such as fatty acids or steroid hormones across the cell membrane?

Such molecules diffuse freely.

You have fused a mouse cell and a human cell and then treated the cell with specific antibodies that are covalently linked to fluorescent dyes (antibodies to mouse proteins - green; antibodies to human proteins - red). What does the cell look like about 40 minutes to an hour after fusion?

The red and green labels are uniformly distributed across the entire membrane.

Which of the following statements is FALSE regarding liposomes?

They are normally found within the bloodstream of eukaryotes.

Which one of the following statements about peripheral membrane proteins is FALSE?

They have domains that protrude from both the extracellular and the cytoplasmic sides of the membrane.

Membranes can be found in all of the following EXCEPT __________.

a ribosome.