5 Written questions
5 Matching questions
- Which membrane protein would be used to move glucose across a membrane from a region of higher concentration to a region of lower concentration?
b) No protein is necessary.
d) Ion channel
- 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
- 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.
- 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 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 a) Transporter
(The GLUT-1 transporter assists the diffusion of glucose through the membrane.)
- b 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.)
- c 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.)
- d c) against the molecule's concentration gradient
- e 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.)
5 Multiple choice questions
- 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.)
- b) The polarity of membrane phospholipids
- 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) 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.)
5 True/False questions
What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?
a) Hydrophobic nature
c) Amphipathic nature
d) Solubility in water → c) Amphipathic nature
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 → a) Sodium-potassium pump
(This pump uses the energy provided by ATP hydrolysis to transport sodium and potassium ions across the membrane.)
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.)
What name is given to the process by which water crosses a selectively permeable membrane?
e) passive transport → c) Amphipathic nature
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 (Osmosis is the diffusion of water across a selectively permeable membrane.)