Chapter 5: Membrane Structure and Function

Which of the following processes includes all others?

passive transport

The formulation of a model for a structure or for a process serves which of the following purposes?

It functions as a testable hypothesis.

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

transmembrane protein

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

embedded in a lipid bilayer.

What are the membrane structures that function in active transport?

integral proteins

What is the voltage across a membrane called?

membrane potential

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

A cell's ability to distinguish one type of neighboring cell from another.

If a membrane protein in an animal cell is involved in the cotransport of glucose and sodium ions into the cell, which of the following is most likely true?

A substance that blocked sodium ions from binding to the cotransport protein would also block the transport of glucose.

Which of the following is true of the evolution of cell membranes?

As populations of organisms evolve, different properties of their cell membranes are selected for or against.

Which of the following is one the ways that the membranes of winter wheat are able to remain fluid when is extremely cold?

By increasing the percentage of unsaturated phospholipids in the membrane.

(Cystic fibrosis is a genetic disease in humans in which chloride ion channels in cell membranes are missing or nonfunctional) Chloride ion channels are membrane structures that include which of the following?

C) hydrophilic proteins

Which of the following would likely move through the lipid bilayer of a plasma membrane most rapidly?

CO2

Cell membranes are asymmetrical. Which of the following is a most likely explanation?

Cell membrane proteins are determined as the membrane is being packaged in the ER and Golgi

Proton pumps are used in various ways by members of every kingdom of organisms. What does this most probably mean?

Cells with proton pumps were maintained in each Kingdom by natural selection.

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

Certain proteins are unique to each membrane

Who was/were the first to propose that cell membranes are phospholipid bilayers?

E. Gorter and F.Grendel

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 statements is correct about diffusion?

It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration

The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on?

It will be on the cytoplasmic side of the ER.

Which of the following membrane activities require energy from ATP hydrolysis?

Na+ ions moving out of the cell

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

Phospholipids and proteins

In the years since the proposal of the fluid mosaic model of the cell membrane, which of the following observations has been added to the model?

The concentration of protein molecules is now known to be much higher.

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 for kinks in the fatty acid tails,forcing adjacent lipids to be further apart.

When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that

The hydrophobic interactions that hold the membrane together are weakest at this point.

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?

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?

They are usually transmembrane proteins.

According to the fluid mosaic model of cell membranes , which is true about the membrane phospholipids?

They can move laterally along the plane of the membrane.

Which of the following factors would tend to increase membrane fluidity?

a greater proportion of unsaturated phospholipids

In which of the following would there be the greatest need for osmoregulation?

a terrestrial animal such as a snake

What kinds of molecules pass through a cell membrane most easily?

small and hydrophobic

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

amphipathic

What mechanisms do plants use to load sucrose produced by photosynthesis into specialized cells in the veins of leaves?

an electrogenic pump a proton pump a contransport protein

The movement of potassium into an animal cell requires

an energy source such as ATP or a proton gradient.

(Cystic fibrosis is a genetic disease in humans in which chloride ion channels in cell membranes are missing or nonfunctional) Which of the following would you expect to be a problem for someone with nonfunctional chloride channeling?

buildup of excessive secretions in organs such as lungs

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?

cell-cell recognition

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

contributes to the membrane potential.

In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by

cotransport proteins.

Based on Figure 7.19 in your textbook, which of these experimental treatments would increase the rate of sucrose transport into the cell?

decreasing extracellular pH

Familial hypercholesterolemia is characterized by which of the following?

defective LDL receptors on the cell membranes

Ions diffuse across membranes down their

electrochemical gradients.

The presence of cholesterol in the plasma membrane 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

Several seriously epidemic viral diseases of earlier centuries were then incurable because they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed which of the following?

hydrating drinks that include high concentrations of salts and glucose

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are

hypertonic to fresh water but hypotonic to the salt solution.

(Cystic fibrosis is a genetic disease in humans in which chloride ion channels in cell membranes are missing or nonfunctional.) If a young male child has cystic fibrosis, which of the following would affect his fertility?

incorrect concentrations of ions in semen

When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are

integral proteins

Which of these are attached to the extracellular matrix?

integrins

A cell whose cytoplasm has a concentration of 0.02 molar glucose is placed in a test tube of water containing 0.02 molar glucose. Assuming that glucose is not actively transported into the cell, which of the following terms describes the tonicity of the external solution relative to the cytoplasm of the cell?

isotonic

Water passes quickly through cell membranes because

it moves through aquaporins in the membrane

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 these are not embedded in the lipid bilayer at all?

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

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.

You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule enters the cell?

similarity of the drug molecule to other molecules transported by the target cells

When a plant cell, such as one from a peony stem, is submerged in a very hypotonic solution, what is likely to occur?

the cell will become turgid

After a membrane freezes and then thaws, it often becomes leaky to solutes. The most reasonable explanation for this is that

the integrity of the lipid bilayer is broken when the membrane freezes.