5 Written Questions
5 Matching Questions
- 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.
- Which of the following transporters does not use passive transport to move molecules across a membrane?
a) Sodium-potassium pump
b) Gramicidin ion channel
d) GLUT-1 glucose transporter
- True or false? Osmosis is a type of diffusion.
- 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.
- 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
- a b) The polarity of membrane phospholipids
- b True (Osmosis is the diffusion of water across a selectively permeable membrane.)
- c True (The hydrophilic, or water-loving, portion of a phospholipid is the polar head, whereas the hydrophobic portion is the nonpolar tail.)
- d a) Sodium-potassium pump
(This pump uses the energy provided by ATP hydrolysis to transport sodium and potassium ions across the membrane.)
- e 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.)
5 Multiple Choice Questions
- 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.)
(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.)
- a) Transporter
(The GLUT-1 transporter assists the diffusion of glucose through the membrane.)
- a) Oxygen (O2) (Small nonpolar molecules such as oxygen can diffuse across cell membranes.)
5 True/False Questions
What name is given to the process by which water crosses a selectively permeable membrane?
e) passive transport → c) Amphipathic nature
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.)
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 property of dishwashing liquid (detergent) makes it useful to wash grease from pans?
a) Hydrophobic nature
c) Amphipathic nature
d) Solubility in water → a) osmosis (Osmosis is the passive transport of water.)
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.