MasteringBio Chapter 7 Practice Test

The internal solute concentration of a plant cell is about 0.8 M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution? 0.8 M 1.0 M 0.4 M distilled water 150 mM.

1.0 M

Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell _____ because _____. B ... the gradient of oxygen is oriented in the opposite direction compared to cell A B ... the oxygen molecules inside cell B have a higher kinetic energy A ... its membrane transport proteins will not be saturated A ... the diffusion gradient there is shallower B ... the diffusion gradient in cell B is steeper

B ... the diffusion gradient in cell B is steeper

Which of the following statements about cotransport of solutes across a membrane is correct? (eText Concept 7.4) The sodium-potassium pump is an example of a cotransport protein. In cotransport, both solutes that are being transported are moving down their chemical gradients. A cotransport protein is most commonly an ion channel. Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes. Cotransport involves the hydrolysis of ATP by the transporting protein.

Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes.

The discomfort associated with irritable bowel syndrome can be alleviated with low doses of the class of antidepressants that block the reuptake of serotonin from the synaptic cleft (the space between adjacent neurons). Serotonin is a relatively small polar neurotransmitter used to transmit nerve impulses in the nerve tissue in the gut and central nervous system. Serotonin is transported back into the releasing neuron up its concentration gradient and down a sodium gradient. How might an antidepressant block serotonin reuptake by the releasing neuron? (eText Concept 7.4) It could promote exocytosis of serotonin. It could block a cotransporter involved in facilitated diffusion It could block active transport of serotonin back into the cell by blocking a serotonin-sodium symporter. It could block the passive diffusion of serotonin back into the cell by chemically modifying serotonin. It could block receptor-mediated endocytosis.

It could block active transport of serotonin back into the cell by blocking a serotonin-sodium symporter.

Which of the following is a function of membrane proteins and also facilitates tissue formation during embryogenesis? Membrane proteins form channels, which move substances across the membrane. Membrane proteins provide receptors for chemical messengers. Membrane proteins attach the membrane to the cytoskeleton. Membrane proteins with short sugar chains form identification tags that are recognized by other cells. All of the listed responses are correct.

Membrane proteins with short sugar chains form identification tags that are recognized by other cells.

Consider the transport of protons and sucrose into a plant cell by the sucrose-proton cotransport protein. Plant cells continuously produce a proton gradient by using the energy of ATP hydrolysis to pump protons out of the cell. Why, in the absence of sucrose, don't protons move back into the cell through the sucrose-proton cotransport protein? (eText Concept 7.4) Protons are freely permeable through the phospholipid bilayer, so no transport protein is needed for protons. The movement of protons through the cotransport protein cannot occur unless sucrose also moves at the same time. Protons, unlike other substances, do not diffuse down their concentration gradient. Protons cannot move through membrane transport proteins. In the absence of sucrose, the ATP-powered proton pump does not function, so there is no proton gradient.

The movement of protons through the cotransport protein cannot occur unless sucrose also moves at the same time.

Glucose can be moved into cells via two mechanisms. An active transport mechanism can be used when the concentration of glucose inside the cell is higher than the concentration of glucose outside of the cell. This active transport mechanism moves glucose and sodium into the cell at the same time. The glucose moves up its gradient and the sodium moves down its gradient. Which of the following statements about this mechanism is most true? (eText Concept 7.4) The protein that moves the sodium and glucose into the cell is an antiporter. To pump glucose up its concentration gradient, sodium is moving down its concentration gradient. The sodium forms an electrochemical gradient in this mechanism. The first two responses are correct. The second and third responses are correct.

The second and third responses are correct

Which of the following statements about the sodium-potassium pump is correct? (eText Concept 7.4) The sodium-potassium pump moves sodium out of the cell and co-transports protons into the cell, which is the source of energy for the movement of the potassium into the cell. The sodium-potassium pump is an antiporter that results in a net negative charge inside the cell. The sodium-potassium pump is a symporter that results in a net negative charge outside the cell. The sodium-potassium pump transports Na+ and K+ across the plasma membrane in the same direction at the expense of ATP hydrolysis. The sodium-potassium pump uses an existing proton gradient to drive the movement of sodium and potassium ions.

The sodium-potassium pump is an antiporter that results in a net negative charge inside the cell.

A single plant cell is placed in an isotonic solution. Salt is then added to the solution. Which of the following would occur as a result of the salt addition? (eText Concept 7.3) The added salt makes the solution hypotonic compared to the cell. Water will enter the cell by osmosis. There would be no osmotic movement of water in response to the added salt. Water would enter the cell by osmosis, and the cell would swell. Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease. The added salt would enter the cell, causing the cell to take up water and swell.

Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease.

which of these experimental treatments would increase the rate of sucrose transport into the cell? adding an inhibitor that blocks the regeneration of ATP adding a substance that makes the membrane more permeable to hydrogen ions decreasing extracellular pH decreasing cytoplasmic pH decreasing extracellular sucrose concentration

decreasing extracellular pH

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly confined to the hydrophobic interior of the membrane. spread in a continuous layer over the inner and outer surfaces of the membrane. embedded in a lipid bilayer. randomly oriented in the membrane, with no fixed inside-outside polarity. free to depart from the fluid membrane and dissolve in the surrounding solution.

embedded in a lipid bilayer

Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane? (eText Concept 7.5) flip-flop of phospholipids from one side of the plasma membrane to the other and the Golgi active transport and the rough endoplasmic reticulum exocytosis and smooth and rough ER receptor-mediated endocytosis and smooth ER and Golgi endocytosis and Golgi

exocytosis and smooth and rough ER

Which of the following pairs correctly matches a membrane transport process to its primary function? (eText Concept 7.5) phagocytosis ... secretion of large particles from the cell by fusion of vesicles with the plasma membrane exocytosis ... the movement of water and solutes out of the cell by vesicle fusion with the plasma membrane pinocytosis ... the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane osmosis ... passive diffusion of water and small solutes across a membrane None of the above is correct.

pinocytosis ... the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane