Question 1

Which of the following best describes the movement of solutes during passive transport across a biological membrane?

Accepted Answer

Solutes move randomly, but overall from higher to lower concentration without energy input.

Question 2

A defect in which of the following molecules would most dramatically reduce the rate of water diffusion across cell membranes?

Accepted Answer

Aquaporins

Question 3

Which process is responsible for the uptake of large molecules, such as proteins, into a cell by the formation of vesicles from the plasma membrane?

Accepted Answer

Endocytosis

Question 4

Which of the following statements best describes a characteristic feature of integral membrane proteins?

Accepted Answer

They are amphipathic, with at least one hydrophobic region.

Question 5

A red blood cell is placed in a solution containing 1 M glucose. What is the osmolarity of this solution, and what will happen to the cell if the solution is isoosmolar to the cell's cytoplasm?

Accepted Answer

Osmolarity is $1~\mathrm{Osm}$; the cell will remain unchanged.

Question 6

Which of the following is NOT a type of endocytosis?

Accepted Answer

Exocytosis

Question 7

A cell is placed in a hypertonic solution. What will happen to the cell?

Accepted Answer

It will lose water and shrivel.

Question 8

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It uses channel or carrier proteins to move solutes down their concentration gradient.

Question 9

Which equation correctly represents the osmolarity of a 1 M solution of NaCl?

Accepted Answer

$1~\mathrm{M}~\mathrm{NaCl} = 2~\mathrm{Osm}$

Question 10

Which of the following is a direct consequence of the fluid mosaic model of biological membranes?

Accepted Answer

Phospholipids move laterally within the plane of the membrane.

Question 11

Which of the following transport mechanisms is responsible for the release of neurotransmitters from nerve cells?

Accepted Answer

Exocytosis

Question 12

A cell uses a proton pump to move $\mathrm{H}^+$ ions out of the cytoplasm. What type of transport is this, and what is the energy source?

Accepted Answer

Active transport; energy from ATP hydrolysis

Question 13

Which of the following best describes the role of carrier proteins in membrane transport?

Accepted Answer

They facilitate passive movement of specific solutes down their concentration gradient.

Question 14

A solution contains 75 mM NaCl and 50 mM MgCl$_2$. What is the total osmolarity of the solution?

Accepted Answer

$75~\mathrm{mM}~\mathrm{NaCl} = 150~\mathrm{mOsm}$; $50~\mathrm{mM}~\mathrm{MgCl}_2 = 150~\mathrm{mOsm}$; Total = $300~\mathrm{mOsm}$

Question 15

Which of the following statements about tonicity is correct?

Accepted Answer

Tonicity is determined by the concentration of solutes that cannot cross the membrane.

Question 16

Which of the following is an example of receptor-mediated endocytosis?

Accepted Answer

A cell taking up cholesterol by binding LDL particles to specific receptors.

Question 17

Which of the following statements best describes the energy requirements for active transport?

Accepted Answer

Active transport requires energy input, usually from ATP, to move solutes against their concentration gradient.

Question 18

Which process allows pancreatic islet cells to release insulin into the bloodstream?

Accepted Answer

Exocytosis

Question 19

A cell is placed in a hypotonic solution. What is the most likely outcome for a cell without a cell wall?

Accepted Answer

It will gain water and burst (lyse).

Membrane Structure and Transport: Modes and Mechanisms

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