5 Written questions
5 Matching questions
- What name is given to the process by which water crosses a selectively permeable membrane?
e) passive transport
- 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.
- What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?
a) Hydrophobic nature
c) Amphipathic nature
d) Solubility in water
- 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?
- 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.
- a a) osmosis (Osmosis is the passive transport of water.)
- b True (The hydrophilic, or water-loving, portion of a phospholipid is the polar head, whereas the hydrophobic portion is the nonpolar tail.)
- c 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.)
- d 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.)
- e c) Amphipathic nature
5 Multiple choice questions
- a) Lipids are mostly nonpolar.
- c) Membrane proteins help move molecules across the membrane.
- 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) Active transport
(Under these conditions, lactose moves against its concentration gradient, so its transport will require energy.)
- True (Osmosis is the diffusion of water across a selectively permeable membrane.)
5 True/False questions
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.)
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 → 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.)
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
d) The amount of cholesterol in the membrane → b) The polarity of membrane phospholipids
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. → 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.)
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.)