Osmosis and tonicity Knowledge-Based Practice

Questions

1. 1.

   Which of the following statements correctly describes the movement of water across the plasma membrane when an animal cell is placed in an isotonic solution?

   • A) Water molecules cease all movement across the plasma membrane due to equal solute concentrations.
   • B) Solute particles rapidly diffuse across the phospholipid bilayer until internal and external water potentials decouple.
   • C) Water molecules diffuse into and out of the cell at equal rates, resulting in no net change in cell volume.
   • D) Water molecules move exclusively into the intracellular fluid until intracellular osmotic pressure reaches zero.
2. 2.

   What occurs when a red blood cell is placed in a hypotonic solution?

   • A) Water moves into the cell by osmosis, causing it to swell and lyse.
   • B) Water moves out of the cell by osmosis, causing it to shrivel and crenate.
   • C) Solute molecules actively diffuse out of the cell, preserving its original volume.
   • D) Water moves across the membrane at equal rates in both directions, leaving cell volume unchanged.
3. 3.

   What occurs when a healthy, turgid plant cell is transferred to a solution with a higher solute concentration than its cytoplasm?

   • A) Water flows into the central vacuole, generating maximum turgor pressure against the cell wall.
   • B) Water moves out of the cell by osmosis, causing the plasma membrane to pull away from the cell wall in plasmolysis.
   • C) The rigid cellulose cell wall softens and bursts due to rapid solute accumulation in the cytosol.
   • D) Water molecules stop crossing the plasma membrane entirely, maintaining a constant protoplast volume.
4. 4.

   Which of the following describes the net movement of water and the resulting change in cell structure when an animal cell is placed into a hypertonic solution?

   • A) Water enters the cell by osmosis, causing the cell to swell and potentially lyse.
   • B) Solute particles rapidly diffuse into the cell, leading to an increase in intracellular volume.
   • C) Water enters and leaves at equal rates, resulting in no net change in the cell's volume or shape.
   • D) Water exits the cell by osmosis, causing the cell to lose volume and shrivel.
5. 5.

   What will occur when a healthy plant cell is placed in a hypotonic solution?

   • A) Water exits the cell down its concentration gradient, causing the plasma membrane to pull away from the cell wall.
   • B) Water enters the cell by osmosis, building turgor pressure against the cell wall until the cell becomes turgid.
   • C) Water moves into and out of the cell at equal rates, causing the cell to become flaccid without any net volume change.
   • D) Water enters the cell continuously because it lacks osmotic regulation, ultimately causing the cell to burst.

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