Diffusion Knowledge-Based Practice

Questions

1. 1.

   Which of the following serves as the direct source of energy that drives the diffusion of solute particles across a cell membrane?

   • A) The intrinsic thermal kinetic energy possessed by the colliding solute particles
   • B) Metabolic energy supplied directly through cellular adenosine triphosphate (ATP) hydrolysis
   • C) Potential energy maintained exclusively by an active proton-motive force across the membrane
   • D) Mechanical tension generated by the continuous contraction of cytoskeletal microfilaments
2. 2.

   What occurs when a diffusible solute reaches dynamic equilibrium across a biological membrane?

   • A) Solute molecules continue to cross the membrane in both directions at equal rates, resulting in no net change in concentration.
   • B) Solute molecules cease all physical movement across the membrane once the concentrations become equal.
   • C) Solute molecules move preferentially toward the extracellular fluid to re-establish a concentration gradient.
   • D) Solute molecules require cellular ATP consumption to maintain equal concentrations on both sides of the membrane.
3. 3.

   Which of the following substances crosses the phospholipid bilayer of a plasma membrane by simple diffusion without the aid of a transport protein?

   • A) Glucose
   • B) Sodium ion
   • C) Chloride ion
   • D) Oxygen gas
4. 4.

   Which of the following modifications will increase the rate of simple diffusion of a solute across a cellular membrane?

   • A) Decreasing the temperature of the surrounding medium
   • B) Increasing the thickness of the phospholipid bilayer
   • C) Increasing the concentration gradient of the solute between the two sides
   • D) Decreasing the surface area of the cell membrane exposed to the solution
5. 5.

   Which of the following statements correctly describes the net movement of solute molecules during simple diffusion across a cell membrane?

   • A) Solute molecules move against their concentration gradient using chemical energy released from ATP hydrolysis.
   • B) Solute molecules move from an area of lower concentration to an area of higher concentration until a steep gradient is established.
   • C) Solute molecules require membrane-bound vesicles to enclose them and fuse with the lipid bilayer for transport.
   • D) Solute molecules move spontaneously down their concentration gradient from an area of higher concentration to an area of lower concentration.

Answers and step-by-step solutions appear after you finish the test.