Honors Bio Test Chapter 7

Front 1

The first to propose that cell membranes are phospholipid bilayers.

Back 1

E. Gorter and F. Grendel

Front 2

Membranes are a phospholipid bilayer between two layers of hydrophilic proteins.

Back 2

H. Davson and J. Danielli

Front 3

The membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids.

Back 3

S. Singer and G. Nicolson

Front 4

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

Back 4

phospholipids and proteins

Front 5

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

Back 5

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

Front 6

All of the following molecules are part of the cell membrane except

Back 6

nucleic acids.

Front 7

The original model for the bilayer structure of cell membranes, which was prepared in the 1920s, was based on which of the following?

Back 7

the understanding that phospholipids are amphipathic molecules

Front 8

The presence of cholesterol in the plasma membranes of some animals

Back 8

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

Front 9

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

Back 9

They can move laterally along the plane of the membrane.

Front 10

The lateral mobility (fluidity) of lipids and proteins in membranes is a consequence of

Back 10

A and B only

Front 11

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

Back 11

by increasing the percentage of unsaturated phospholipids in the membrane

Front 12

The surface of an integral membrane protein would be best described as

Back 12

amphipathic

Front 13

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

Back 13

integral proteins.

Front 14

All of the following are functions of integral membrane proteins except

Back 14

protein synthesis.

Front 15

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

Back 15

The double bonds form a kink in the fatty acid tail, forcing adjacent lipids to be further apart.

Front 16

Which of the following is correct about integral membrane proteins?

Back 16

They are usually transmembrane proteins.

Front 17

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

Back 17

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

Front 18

What is one of the functions of cholesterol in animal cell membranes?

Back 18

maintains membrane fluidity

Front 19

What membrane-surface molecules are thought to be most important as cells recognize each other?

Back 19

glycoproteins

Front 20

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

Back 20

cell-cell recognition

Front 21

Which of the following adheres to the extracellular surface of animal cell plasma membranes?

Back 21

fibers of the extracellular matrix

Front 22

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

Back 22

small and hydrophobic

Front 23

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

Back 23

It exhibits a specificity for a particular type of molecule.

Front 24

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

Back 24

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

Front 25

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

Back 25

CO2

Front 26

The selective permeability of biological membranes is dependent on which of the following?

Back 26

A and B only

Front 27

Which of the following statements is correct about diffusion?

Back 27

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

Front 28

Water passes quickly through cell membranes because

Back 28

it moves through aquaporins in the membrane.

Front 29

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?

Back 29

The patient's red blood cells will swell because the blood fluid is hypotonic compared to the cells.

Front 30

.

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

Back 30

hypertonic to fresh water but hypotonic to the salt solution.

Front 31

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?

Back 31

isotonic

Front 32

Which of the following statements correctly describes the normal tonicity conditions for typical plant and animal cells?

Back 32

The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution.

Front 33

.

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 not be a factor that determines whether the molecule enters the cell?

Back 33

lipid composition of the target cells' plasma membrane

Front 34

All of the following membrane activities require energy from ATP hydrolysis except

Back 34

facilitated diffusion.

Front 35

What are the membrane structures that function in active transport?

Back 35

integral proteins

Front 36

The movement of a substance across a biological membrane against its concentration gradient with the help of energy input is

Back 36

active transport.

Front 37

Carrier molecules in the membrane and metabolic energy are required for

Back 37

active transport.

Front 38

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?

Back 38

facilitated diffusion

Front 39

The main difference(s) between facilitated diffusion and active transport is (are)

Back 39

A, B, and C

Front 40

What is the voltage across a membrane called?

Back 40

membrane potential

Front 41

.

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

Back 41

cotransport proteins.

Front 42

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

Back 42

contributes to the membrane potential.

Front 43

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 not true?

Back 43

Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell.

Front 44

The movement of potassium into an animal cell requires

Back 44

an energy source such as ATP or a proton gradient.
d.
a cotransport protein.

Front 45

Ions diffuse across membranes down their

Back 45

electrochemical gradients.

Front 46

Which of the following characterizes the sodium-potassium pump?

Back 46

Only A and B are correct.

Front 47

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

Back 47

A and C only

Front 48

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?

Back 48

It will be on the cytoplasmic side of the ER.

Front 49

Which of the following statements about membrane structure and function is false?

Back 49

The types of proteins that are exposed on one side of a membrane are nearly identical to those exposed on the other side of the membrane.

Front 50

All of the following processes take material into cells except

Back 50

exocytosis.

Front 51

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

Back 51

phagocytosis

Front 52

The membrane activity most nearly opposite to exocytosis is

Back 52

phagocytosis.

Front 53

White blood cells engulf bacteria through what process?

Back 53

phagocytosis

Front 54

What is the cause of familial hypercholesterolemia?

Back 54

defective LDL receptors on the cell membranes

Front 55

In addition to exporting materials from the cytoplasm of the cell, the process of exocytosis is also important in

Back 55

the production of cell walls by plant cells.

Front 56

The difference between pinocytosis and receptor-mediated endocytosis is that

Back 56

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