Bio Unit 1: Membrane Structure/Function

Aquaporins are proteins that facilitate the transport of __________ across the membrane. a) urine b) water c) proteins d) salt

b

How do fatty acids travel through a cell membrane? a) endocytosis b) carrier proteins c) diffusion d) active transport

b

Overall, membranes seem to have a great deal in common, but on closer inspection it is revealed that membranes of different cells have unique properties. What is the primary component of membranes that gives membranes cell-specific properties? a) cholesterol b) proteins c) phospholipids d) cytoskeleton

b

The sodium-potassium pump uses energy from ATP to move sodium ions out of the cell, and potassium ions into the cell. This is an example of a) exocytosis. b) active transport. c) diffusion. d) passive transport. e) facilitated diffusion.

b

Which of the following enables a cell to pick up and concentrate a specific kind of molecule? a) passive transport b) receptor-mediated endocytosis c) diffusion d) osmosis

b

The concentration of solutes in a red blood cell is about 2%. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions? a) a hypertonic urea solution b) a hypotonic sucrose solution c) a hypertonic sucrose solution d) a hypotonic urea solution

c

The fluid mosaic model describes the plasma membrane as consisting of a) a phospholipid bilayer with embedded carbohydrates. b) two layers of phospholipids with cholesterol sandwiched between them. c) diverse proteins embedded in a phospholipid bilayer. d) carbohydrates and phospholipids that can drift in the membrane.

c

Water crosses the plasma membrane a) against its concentration gradient. b) through cotransport.through facilitated diffusion or diffusion. c) through active transport. d) using a process that requires energy from the cell.

c

A group of single-cell organisms collected from the ocean was brought into the lab for examination. The lab assistant was concerned that the water had become full of toxic waste products and so added clean water to the culture. All of the organisms died, and when she looked at them under the microscope, all she could see were bits and pieces of them scattered throughout the water. What likely happened? a) She added water that was hypotonic to the culture of organisms, and they ruptured. b) She added too little salt to the seawater she added, and the organisms all lost too much water and shriveled up. c) She added seawater to which she had added too much salt, and they ruptured. d) She added water isotonic to the organisms, causing too much water to move in and out of the organisms, and they ruptured.

a

Which of these is hydrophobic like the interior of the plasma membrane? a) lipid soluble molecule b) water c) glucose d) hydrogen ion

a

What controls the net direction of molecules, such as oxygen, involved in passive transport? a) the type of cell to or from which the oxygen molecule is moving b) the direction of the oxygen concentration gradient c) the size of the oxygen molecule d) the amount of energy available to transport oxygen

b

Which of these statements describes what occurs in facilitated diffusion? a) Facilitated diffusion of solutes occurs through phospholipid pores in the membrane. b) Facilitated diffusion of solutes occurs through protein pores in the membrane. c) Facilitated diffusion requires energy from the cell to drive a concentration gradient. d) Facilitated diffusion is another name for osmosis.

b

Cells A and B are the same size and shape, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell _____ because _____. a) B ... the oxygen molecules inside cell B have a higher kinetic energy b) A ... its membrane transport proteins will not be saturated c) B ... the diffusion gradient there is steeper d) A ... the diffusion gradient there is shallower

c

In active transport, a) a vesicle inside the cell fuses with the plasma membrane and releases its contents outside the cell. b) molecules move across the plasma membrane by crossing the lipid bilayer directly, rather than by using a transport protein. c) molecules move across the plasma membrane against their concentration gradient. d) the plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. e) no energy input is required from the cell.

c

Plasma membranes are selectively permeable. This means that a) plasma membranes must be very thick. b) anything can pass into or out of a cell as long as the membrane is intact and the cell is healthy. c) the plasma membrane allows some substances to enter or leave a cell more easily than others. d) glucose cannot enter the cell.

c

Some protozoans have special organelles called contractile vacuoles that continually eliminate excess water from the cell. The presence of these organelles tells you that the environment a) is isotonic to the protozoan. b) contains a higher concentration of solutes than the protozoan. c) is hypotonic to the protozoan. d) is hypertonic to the protozoan.

c

The lipids in a cell membrane are arranged _____. a) so that the hydrophilic components are arranged to face each other b) on either side of a single layer of protein c) between two layers of protein d) so that the nonpolar parts of two lipids point toward each other

d

The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. This describes the process of a) active transport. b) exocytosis. c) passive transport. d) endocytosis. e) diffusion.

d

Which characteristic promoted the utilization of lipids as the first cell membrane? a) ability to form an impermeable membrane b) formation of a semi-solid membrane c) spontaneous degradation of the intracellular environment d) self-assembly into a simple membrane

d

Which of the following is an accurate comparison of active transport and facilitated diffusion? a) Facilitated diffusion requires the use of ATP; active transport does not require ATP. b) In both types of movement, phosphate groups alter the shape of transport proteins. c) Active transport requires membrane proteins; facilitated diffusion does not require membrane proteins. d) Active transport moves solutes against their concentration gradient; facilitated diffusion moves substances down their concentration gradient.

d

A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of a) endocytosis. b) exocytosis. c) active transport. d) diffusion. e) facilitated diffusion.

e