Mastering Biology Osmosis and Diffusion

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Which of the following factors does not affect membrane permeability?

a) The saturation of hydrocarbon tails in membrane phospholipids

b) The polarity of membrane phospholipids

c) Temperature

d) The amount of cholesterol in the membrane

b) The polarity of membrane phospholipids

How can a lipid be distinguished from a sugar?

a) Lipids are mostly nonpolar.
b) Lipids are mostly saturated.
c) A lipid dissolves in water.
d) A lipid is made up of only hydrocarbons.

a) Lipids are mostly nonpolar.

True or false? Osmosis is a type of diffusion.

True (Osmosis is the diffusion of water across a selectively permeable membrane.)

What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?

a) Hydrophobic nature
b) Permeability
c) Amphipathic nature
d) Solubility in water

c) Amphipathic nature

Which of the following particles could diffuse easily through a cell membrane?

a) Oxygen (O2)
b) Hydrogen ion (H+)
c) Sodium ion (Na+)
d) Glucose

a) Oxygen (O2) (Small nonpolar molecules such as oxygen can diffuse across cell membranes.)

True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.

True (The hydrophilic, or water-loving, portion of a phospholipid is the polar head, whereas the hydrophobic portion is the nonpolar tail.)

If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?

a) Hypotonic
b) Hypertonic
c) Osmotic
d) Isotonic

a) Hypotonic (The salt concentration in the solution is lower than it is in the cell, so water enters the cell, causing it to burst.)

What name is given to the process by which water crosses a selectively permeable membrane?

a) osmosis
b) diffusion
c) pinocytosis
d) phagocytosis
e) passive transport

a) osmosis (Osmosis is the passive transport of water.)

Lipid vesicles are formed so that they contain pure water. If these vesicles are transferred to a solution that contains a rather high concentration of solutes, what will be the net direction of water movement?

a) It will not move at all.

b) It depends on what solute is dissolved in the exterior solution.

c) It will move out of the vesicles.

d) It will move into the vesicles.

c) It will move out of the vesicles.

A semipermeable membrane is placed between the following solutions. Which solution will decrease in volume?

a) Solution A: 1.4% (m/v) starch
b) Solution B: 7.62% (m/v) starch

a) Solution A: 1.4% (m/v) starch (The water molecules actually move in both directions, but they move to a greater extent toward Solution B because it has a higher solute concentration than Solution A. The net movement of water molecules causes Solution A to decrease in volume and Solution B to increase in volume.)

A semipermeable membrane is placed between the following solutions. Which solution will increase in volume?

a) Solution C: 9% (m/v) NaCl
b) Solution D: 12.4% (m/v) NaCl

b) Solution D: 12.4% (m/v) NaCl (The water molecules actually move in both directions, but they move to a greater extent toward Solution D because it has a higher solute concentration than Solution C. This net movement of water molecules causes Solution D to increase in volume and Solution C to decrease in volume.)

What distinguishes facilitated diffusion from simple diffusion?

a) Molecules move from a region of lower concentration to a region of higher concentration.

b) No energy is used to move molecules across the membrane.

c) Membrane proteins help move molecules across the membrane.

d) Molecules move from a region of higher concentration to a region of lower concentration.

c) Membrane proteins help move molecules across the membrane.

Which of the following transporters does not use passive transport to move molecules across a membrane?



a) Sodium-potassium pump
b) Gramicidin ion channel
c) Valinomycin
d) GLUT-1 glucose transporter

a) Sodium-potassium pump
(This pump uses the energy provided by ATP hydrolysis to transport sodium and potassium ions across the membrane.)

True or false? Active transport differs from passive transport in that active transport does not require an input of energy.

False

Which membrane protein would be used to move glucose across a membrane from a region of higher concentration to a region of lower concentration?

a) Transporter
b) No protein is necessary.
c) Pump
d) Ion channel

a) Transporter

(The GLUT-1 transporter assists the diffusion of glucose through the membrane.)

Which of the following statements is true about the net movement of an ion across a membrane by passive diffusion through a membrane channel?

a) The charge on the other side of the membrane is generally the opposite of the ion's charge.

b) There is a higher concentration of ions on the side of the membrane toward which the ion diffuses.

c) For every ion that diffuses through the membrane, a different ion diffuses in the opposite direction.

d) The cell expends energy as the ion passes through the membrane.

a) The charge on the other side of the membrane is generally the opposite of the ion's charge.

(Ions tend to move toward regions of unlike charge.)

True or false? During active transport through the sodium-potassium pump, ATP hydrolysis provides the energy to pump three sodium ions into the cell for every two potassium ions pumped out of the cell.

False
(The sodium-potassium pump maintains a state in which the concentration of sodium is low inside the cell relative to the outside and the concentration of potassium is high inside the cell relative to the outside; thus, three sodium ions are pumped out of the cell and two potassium ions are pumped into the cell against the electrochemical gradient.)

Lactose transport by membrane proteins occurs under conditions in which the concentration of lactose inside the cell is higher than the concentration outside the cell. What type of transport is used to move lactose into the cell?

a) Active transport
b) Simple diffusion
c) Facilitated diffusion
d) Osmosis

a) Active transport

(Under these conditions, lactose moves against its concentration gradient, so its transport will require energy.)

In cells, membrane proteins are responsible for the passage of substances that can't cross the membrane on their own. Channels and transporters are involved in facilitated diffusion. Pumps are involved in active transport. In terms of their properties or functions, which statement most accurately describes how these three types of membrane proteins compare?

a) Among the three types, only pumps are thought to undergo a shape change as part of their function.

b) Pumps are selective; channels and transporters are not selective.

c) Channels and transporters are integral membrane proteins; pumps are peripheral membrane proteins.

d) Among the three types, only pumps can concentrate substances on one side of the membrane.

d) Among the three types, only pumps can concentrate substances on one side of the membrane.

(Only pumps use energy (from ATP) to move substances against electrochemical gradients.)

The movement of molecules through a plasma membrane channel protein is always _____.

a) toward the inside of the cell

b) down the molecule's concentration gradient

c) against the molecule's concentration gradient

d) "paid for" by an expenditure of cellular energy

c) against the molecule's concentration gradient

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