Biology 121 Chapter 7

Front 1

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

Back 1

E. Gorter and F. Grendel

Front 2

Who proposed that membranes are a phospholipid bilayer between two layers of hydrophilic proteins?

Back 2

H. Davson and J. Danielli

Front 3

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 3

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

Front 4

The presence of cholesterol in the plasma membranes of some animals

Back 4

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

Front 5

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

Back 5

They can move laterally along the plane of the membrane

Front 6

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

Back 6

amphipathic

Front 7

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

Back 7

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

Front 8

Which of the following is true of integral membrane proteins

Back 8

They are usually transmembrane proteins

Front 9

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

Back 9

cell-cell recognition

Front 10

Which of these are not embedded in the lipid bilayer at all

Back 10

peripheral proteins

Front 11

Which of these are attached to the extracellular matrix

Back 11

integrins

Front 12

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

Back 12

glycoproteins

Front 13

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

Back 13

It exhibits a specificity for a particular type of molecule

Front 14

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

Back 14

CO2

Front 15

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

Back 15

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

Front 16

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

Back 16

the cell will become turgid

Front 17

Which of the following membrane activities require energy from ATP hydrolysis

Back 17

Na+ions moving out of the cell

Front 18

What are the membrane structures that function in active transport

Back 18

integral proteins

Front 19

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 19

facilitated diffusion

Front 20

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 20

cotransport proteins

Front 21

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

Back 21

contributes to the membrane potential

Front 22

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

Back 22

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

Front 23

The movement of potassium into an animal cell requires

Back 23

an energy source such as ATP or a proton gradient

Front 24

Ions diffuse across membranes down their

Back 24

electrochemical gradients

Front 25

White blood cells engulf bacteria through what process

Back 25

phagocytosis

Front 26

The difference between pinocytosis and receptor-mediated endocytosis is that

Back 26

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

Front 27

In what way do the membranes of a eukaryotic cell vary

Back 27

Certain proteins are unique to each membrane

Front 28

Which of the following factors would tend to increase membrane fluidity

Back 28

a greater proportion of unsaturated phospholipids