Membrane Structure/Function

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

Active transport moves solutes against their concentration gradient; facilitated diffusion moves substances down their concentration gradient.

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 _____.

B ... the diffusion gradient there is steeper

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

Facilitated diffusion of solutes occurs through protein pores in the membrane.

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?

She added water that was hypotonic to the culture of organisms, and they ruptured.

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 hypertonic sucrose solution a hypertonic urea solution a hypotonic sucrose solution a hypotonic urea solution

a hypertonic sucrose solution

Small, nonpolar, hydrophobic molecules such as fatty acids easily pass through...

a membrane's lipid bilayer

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

active transport

The fluid mosaic model describes the plasma membrane as consisting of

diverse proteins embedded in a phospholipid bilayer.

The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. This describes the process of

endocytosis

A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of

facilitated diffusion

What condition might result from an excess of aquaporins? fluid retention in pregnant women dehydration hereditary diabetes insipidus malaria

fluid retention in pregnant women

Exocytosis?

going from inside to outside cell

Endocytosis?

going from outside to inside of cell

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 (hypotonic/hypertonic/isotonic to protozoan)

hypotonic

You're on the pilot episode of a new reality show called "The Transport Factor." The host hands you three different amino acids, four different sugars, and two different ions. Then the host shouts, "How many different proteins does the cell need to move these molecules across the plasma membrane using facilitated transport?" Quickly, you correctly respond: _____.

nine

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?

proteins

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

receptor-mediated endocytosis

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

self-assembly into a simple membrane

The lipids in a cell membrane are arranged _____.

so that the nonpolar parts of two lipids point toward each other

What controls the direction of a molecule, such as oxygen, involved in passive transport?

the direction of the oxygen concentration gradient

In active transport, molecules move across...

the plasma membrane against their concentration gradient.

Plasma membranes are selectively permeable. This means that

the plasma membrane allows some substances to enter or leave a cell more easily than others.

Water crosses the plasma membrane

through facilitated diffusion or diffusion

What substance is transported by aquaporins?

water