Bio 150 Chapter 7

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly? A) CO2 B) an amino acid C) glucose D) K+ E) starch

CO2

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane.

Why are lipids and proteins free to move laterally in membranes?

Hydrophilic portions of the lipids are in the interior of the membrane.

Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

It exhibits a specificity for a particular type of molecule.

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep any membrane more fluid at lower temperatures?

The double bonds form kinks in the fatty acid tails, forcing adjacent lipids to be further apart.

A patient has had a serious accident and lost a lot of blood. In an attempt to replenish body fluids, distilled water, equal to the volume of blood lost, is transferred directly into one of his veins. What will be the most probable result of this transfusion? A) It will have no unfavorable effect as long as the water is free of viruses and bacteria. B) The patientʹs red blood cells will shrivel up because the blood fluid is hypotonic compared to the cells. C) The patientʹs red blood cells will swell because the blood fluid is hypotonic compared to the cells. D) The patientʹs red blood cells will shrivel up because the blood fluid is hypertonic compared to the cells. E) The patientʹs red blood cells will burst because the blood fluid is hypertonic compared to the cells.

The patientʹs red blood cells will swell because the blood fluid is hypotonic compared to the cells.

Which of the following is true of integral membrane proteins? A) They lack tertiary structure. B) They are loosely bound to the surface of the bilayer. C) They are usually transmembrane proteins. D) They are not mobile within the bilayer. E) They serve only a structural role in membranes.

They are usually transmembrane proteins.

According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids? A) They can move laterally along the plane of the membrane. B) They frequently flip-flop from one side of the membrane to the other. C) They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane. D) They are free to depart from the membrane and dissolve in the surrounding solution. E) They have hydrophilic tails in the interior of the membrane.

They can move laterally along the plane of the membrane.

Of the following functions, which is most important for the glycoproteins and glycolipids of animal cell membranes?

a cellʹs ability to distinguish one type of neighboring cell from another

Which of the following factors would tend to increase membrane fluidity? A) a greater proportion of unsaturated phospholipids B) a greater proportion of saturated phospholipids C) a lower temperature D) a relatively high protein content in the membrane E) a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses

a greater proportion of unsaturated phospholipids

In order for a protein to be an integral membrane protein it would have to be which of the following?

amphipathic

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function? A) transporting ions against an electrochemical gradient B) cell-cell recognition C) maintaining fluidity of the phospholipid bilayer D) attaching to the cytoskeleton E) establishing the diffusion barrier to charged molecules

cell-cell recognition

The sodium-potassium pump is called an electrogenic pump because it

contributes to the membrane potential.

Ions diffuse across membranes down their

electrochemical gradients.

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

embedded in a lipid bilayer.

The presence of cholesterol in the plasma membranes of some animals

enables the membrane to stay fluid more easily when cell temperature drops.

Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?

facilitated diffusion

Which of these often serve as receptors or cell recognition molecules on cell surfaces?

glycoproteins

What are the membrane structures that function in active transport?

integral proteins

Which of these are attached to the extracellular matrix?

integrins

Water passes quickly through cell membranes because

it moves through aquaporins in the membrane.

What is the voltage across a membrane called?

membrane potential

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?

on the inside surface of the vesicle

Which of the following processes includes all others? A) osmosis B) diffusion of a solute across a membrane C) facilitated diffusion D) passive transport E) transport of an ion down its electrochemical gradient

passive transport

Which of these are not embedded in the lipid bilayer at all? A) transmembrane proteins B) integral proteins C) peripheral proteins D) integrins E) glycoproteins

peripheral proteins

An organism with a cell wall would have the most difficulty doing which process?

phagocytosis

White blood cells engulf bacteria through what process?

phagocytosis

Which of the following types of molecules are the major structural components of the cell membrane?

phospholipids and proteins

The difference between pinocytosis and receptor-mediated endocytosis is that

pinocytosis brings only water into the cell, but receptor-mediated endocytosis brings in other molecules as well.

What kinds of molecules pass through a cell membrane most easily? A) large and hydrophobic B) small and hydrophobic C) large polar D) ionic E) monosaccharides such as glucose

small and hydrophobic

Which of the following span the phospholipids bilayer, usually a number of times?

transmembrane proteins