Ch. 5: Membrane Transport & Cell Signaling

Question 1

What event would activate a G protein?

Answer 1

replacement of GDP with GTP

Question 2

Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found?

Answer 2

In the interior of the membrane

Question 3

Which of the following enables a cell to concentrate and take in a specific kind of molecule?

Answer 3

Receptor-mediated endocytosis

Question 4

The concentration of solutes in a particular cell is about 2%, but the cell contains almost no sucrose or urea. Sucrose cannot pass through the membrane of this cell, but water and urea can. Osmosis would cause this cell to shrink the most when immersed in which of the following solutions?

Answer 4

A hypertonic sucrose solution

Question 5

Receptors for signal molecules may be found where?

Answer 5

may be found embedded in the plasma membrane or found within the cytoplasm or nucleus

Question 6

Second messengers tend to be water-soluble and small. This accounts for their ability to __________.

Answer 6

rapidly move throughout the cell by diffusion

Question 7

The plasma membrane is referred to as a “fluid mosaic” structure. Which of the following statements about that model is true?

Answer 7

The fluid aspect of the membrane is due to the lateral and rotational movement of phospholipids, and embedded proteins account for the mosaic aspect.

Question 8

Which of the following correctly describes a general property of all electrogenic pumps?

Answer 8

They create a voltage difference across a membrane.

Question 9

Which of the following pairs correctly matches a membrane transport process to its primary function?

Answer 9

Pinocytosis; the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane

Question 10

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because __________.

Answer 10

they amplify the original signal manyfold

Question 11

Early work on signal transduction and glycogen metabolism by Sutherland indicated that __________.

Answer 11

the signal molecule did not interact directly with the cytosolic enzyme but required an intact plasma membrane before the enzyme could be activated

Question 12

Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?

Answer 12

Membrane carbohydrates have a primary role in cell-cell recognition.

Question 13

Which of the following processes and organelle(s) account for the replacement of lipids and proteins lost from the plasma membrane?

Answer 13

Exocytosis and smooth and rough ER

Question 14

The molecule cAMP directly activates __________.

Answer 14

protein kinase A

Question 15

Which of these statements describes some aspect of facilitated diffusion?

Answer 15

Facilitated diffusion of solutes may occur through transport proteins in the membrane.

Question 16

In what way do the membranes of eukaryotic cells vary

Answer 16

Certain proteins are unique to the membrane of each cell type.

Question 17

Steroid hormones enter a cell by simple diffusion. In doing so, these steroids __________.

Answer 17

None of the listed responses is correct.

(Steroids move down concentration gradient, are small enough, or nonpolar, or hydrophobic)

Question 18

Which of the following molecules is most likely to passively diffuse across the plasma membrane?

Answer 18

Carbon dioxide

Question 19

Which of the following statements about passive transport is correct?

Answer 19

Passive transport involves movement of solute in both directions across a membrane, but with a net movement of solute down its concentration gradient.

Question 20

Which of the following processes includes all the others?

Answer 20

Passive transport

Question 21

Which of the following would tend to increase membrane fluidity?

Answer 21

A greater proportion of phospholipids with unsaturated hydrocarbon tails

Question 22

The general name for an enzyme that transfers phosphate groups from ATP to a protein is __________.

Answer 22

protein kinase

Question 23

Testosterone, a lipid-soluble signaling molecule, crosses the membranes of cells throughout the body but affects only target cells because __________.

Answer 23

intracellular receptors for testosterone are present only in target cells

Question 24

Nitric oxide is unusual among animal signal molecules in that it __________.

Answer 24

is a gas

Question 25

Which of the following would be least likely to pass through a plasma membrane without the help of a transport protein?

Answer 25

A large polar molecule