Cell Phys Osmolarity Review Questions

1. What is osmosis?

a) Movement of solute molecules through a membrane

b) Movement of solvent molecules through a selectively permeable membrane

c) Equilibration of solute concentrations in a solution

d) Movement of water molecules against their concentration gradient

b) Movement of solvent molecules through a selectively permeable membrane

Explanation: Osmosis is the movement of solvent molecules, such as water (H2O), through a selectively permeable membrane into a region of higher solute concentration, equilibrating the solute concentrations on the two sides. The solvent moves down its concentration gradient.

2. In an isotonic solution, a cell will:

a) swell

b) shrink

c) shrink then swell

d) swell then shrink

e) neither shrink nor swell

e) neither shrink nor swell

An isotonic solution has the same osmolarity as inside a cell.

3. Which of the following is true?

a) Osmotically active solutes cross cell membranes

b) Water is actively transported across cell membranes

c) Aquaporins facilitate water movement through cell membranes

d) Water cannot ever cross cell membranes

c) Aquaporins facilitate water movement through cell membranes

4. In a hypertonic solution there is

a) A net movement of water into the cell

b) A net movement of water out of the cell

c) A net movement of osmotically active solute out of the cell

d) No net water movement across the cell membrane

b) A net movement of water out of the cell

Explanation: In a hypertonic solution, there is a higher solute concentration outside the cell, causing a net movement of water out of the cell and cell shrinking.

5. What is osmolarity?

a) The movement of osmotically active solute molecules

b) The concentration of osmotically active solute

c) The equilibration of solute concentrations across the cell membrane

d) The concentration of osmotically inactive solute

b) The concentration of osmotically active solute

Explanation: Osmolarity is the measure of solute concentration, defined as the number of osmoles (Osm) of solute per liter (L) of solution (osmol/L or Osm/L).

6. How is osmolarity calculated?

a) Molarity multiplied by the osmotically active weight of the solute

b) Molarity divided by the number of osmotically active particles

c) Molarity multiplied by the number of osmotically active particles

d) Molarity divided by the osmotically active volume of the solution

c) Molarity multiplied by the number of particles

Explanation: Osmolarity is calculated by multiplying the molarity of the solution by the number of

the osmotically active solute particles.

7. What is the molecular weight of glucose?

a) 58 g/mol

b) 154 g/mol

c) 180 g/mol

d) 308 g/mol

c) 180 g/mol

Explanation: The molecular weight of glucose is 180 g/mol.

8. How does the osmolarity of a NaCl solution differ from the molarity of the solution?

a) Molarity only accounts for the weight of the solute

b) Osmolarity accounts for the moles of solvent

c) Osmolarity accounts for the moles of osmotically active particles

d) Molarity only accounts for the moles of osmotically inactive particles

c) Osmolarity accounts for the moles of osmotically active particles

Explanation: NaCl molarity x2 accounts for the dissociation of the osmotically active solute particles, sodium and chloride ions, in the solution.

9. How are osmoles converted to milliosmoles?

a) Multiply osmoles by the osmotically active particles

b) Multiply molarity by 100

c) Divide osmoles by the osmotically active particles

d) Divide molarity by 100

e) none of the above

e) none of the above

Explanation: To convert osmolarity to milliosmolar, the osmolarity is divided by 1000. Milli = 1000

10. What is the osmolarity of a 0.9% NaCl solution?

a) 154 mOsm

b) 308 mOsm

c) 180 mOsm

d) 58 mOsm

b) 308 mOsm

Explanation: A 0.9% solution is 0.9g of NaCl in 100ml

11. If a solution has a higher osmolarity than a cell, it means:

a) It has fewer solute particles than the cytosol

b) It has more solute particles than the cytosol

c) It is hypotonic

d) It is isotonic

b) It has more solute particles

Explanation: Higher osmolarity indicates a higher concentration of solute particles in the solution.

12. What is the primary factor affecting osmolarity in a solution?

a) Solute concentration

b) Solvent concentration

c) Temperature

d) Pressure

a) Solute concentration

Explanation: The primary factor affecting osmolarity is the concentration of solute particles in the solution.

13. In a hypotonic solution, a cell will

a) swell

b) have a lower intracellular solute concentration than the solution

c) shrink

d) crenate

a) Net influx of water, swell

Explanation: A hypotonic solution causes a net influx of water into the cell.

14. Which of the following is osmotically active?

a) Aquaporins

b) membrane permeant ions

c) membrane impermeant ions

d) Lipids

c) membrane impermeant ions

15. At osmotic equilibrium, solute concentrations

a)  are decreasing inside the cell

b) are increasing inside the cell

c) are constant on both sides of the membrane

d) are osmotically inactive

e) none of the above

c) They remain constant on both sides of the membrane

Explanation: At osmotic equilibrium, solute concentrations remain constant on both sides of the

membrane, indicating an equal distribution of osmotically active solute particles.

What type of volume changes do cells sense?

a) isosmotic volume change

b) Rate of volume change

c) Anisosmotic volume change

d) all of the above

e) none of the above

d) all of the above

Anisosmotic volume change is induced by

a) Changes in cytoplasmic solute content

b) Changes in extracellular osmolarity

c) Both a and b

d) none of the above

b) Changes in extracellular osmolarity

Cells achieve long-term cellular volume control by regulating

a) Water

b) Proteins

c) Intracellular osmolytes

d) Extracellular osmolytes

c) Intracellular osmolytes

The Gibbs-Donnan equilibrium characterized by

a) Equal distribution of diffusible ions

b) Unequal distribution of diffusible ions

c) Unequal distribution of water

d) Equal distribution of water

b) Unequal distribution of diffusible ions

What is the primary cause of Gibbs-Donnan equilibrium in cells?

a) Presence of water

b) Presence of positively-charged proteins

c) Presence of negatively-charged proteins

d) Presence of electrolytes

c) Presence of negatively-charged proteins

How does the Na+/K+ pump keep cells from reaching Gibbs-Donnan equilibration?

a) It ejects 3 Na+ and takes 2 K+ into the cell

b) It releases water from the cell

c) It increases the concentration of Na+ inside the cell

d) It induces cell lysis

a) It ejects 3 Na+ and takes 2 K+ into the cell

What happens to a cell if the Na+/K+ pump stops working?

a) Decreased cell volume

b) Increased cell volume

c) No effect on cell volume

d) Increased protein concentration

b) Increased cell volume

An isosmotic volume change results from

a) Extracellular osmotic perturbations

b) Changes in cytoplasmic solute content

c) Presence of positively-charged proteins

d) Changes in cell color

b) Changes in cytoplasmic solute content

What is the purpose of osmolytes in long-term cellular volume control?

a) To increase cell volume

b) To decrease cell volume

c) To adjust osmotic strength of cytoplasm and maintain volume

d) To induce osmotic swelling

c) To adjust osmotic strength of cytoplasm and maintain volume

What is the main effect of the Na+/K+ pump on cell permeability to NaCl?

a) It makes the cell permeable to NaCl

b) It has no effect on cell permeability

c) It effectively makes the cell impermeable to NaCl

d) It increases NaCl concentration inside the cell

c) It effectively makes the cell impermeable to NaCl