Q: Which of the following equations correctly represents the calculation of molarity ($$M) $$for a glucose solution?

$$M = \frac{\text{moles of glucose}}{\text{liters of solution}}$$

Q: A solution contains 1 mol/L NaCl and 1 mol/L CaCl$$_2. $$What is the total osmolality of the solution?

$$1 \text{ mol/L NaCl} \rightarrow 2 \text{ Osm} \\ 1 \text{ mol/L CaCl}_2 \rightarrow 3 \text{ Osm} \\ \text{Total osmolality} = 5 \text{ Osm}$$

Q: Which of the following is the correct Nernst equation for calculating the equilibrium potential ($$E_{ion}) $$for a monovalent cation at body temperature?

$$E_{ion} = \frac{61}{z} \log \left( \frac{[\text{ion}]_{out}}{[\text{ion}]_{in}} \right)$$

Question 1

Which of the following best describes why charged ions cannot freely cross the plasma membrane?

Accepted Answer

The hydrophobic core of the lipid bilayer repels charged ions, requiring them to use ion channels for transport.

Question 2

A red blood cell is placed in a solution containing 0.5% NaCl. What will most likely happen to the cell, and why?

Accepted Answer

The cell will swell and may burst because the solution is hypotonic relative to the cell's cytoplasm.

Question 3

Which of the following equations correctly represents the calculation of molarity ($$M) $$for a glucose solution?

Accepted Answer

$$M = \frac{	ext{moles of glucose}}{	ext{liters of solution}}$$

Question 4

A solution contains 1 mol/L NaCl and 1 mol/L CaCl$$_2. $$What is the total osmolality of the solution?

Accepted Answer

$$1 	ext{ mol/L NaCl} ightarrow 2 	ext{ Osm} \ 1 	ext{ mol/L CaCl}_2 ightarrow 3 	ext{ Osm} \ 	ext{Total osmolality} = 5 	ext{ Osm}$$

Question 5

Which of the following best explains the function of the Na$$^+/K$^+$$ pump in maintaining membrane potential?

Accepted Answer

It actively transports 3 Na$$^+$$ ions out of the cell and 2 K$$^+$$ ions into the cell, creating an electrochemical gradient.

Question 6

A cell is placed in a 2 Osm glucose solution separated by a membrane from a 1 Osm NaCl solution. The membrane is permeable to water but not to solutes. In which direction will water move?

Accepted Answer

Water will move into the 2 Osm glucose solution because it has a higher total solute concentration.

Question 7

Which of the following statements about osmosis is correct?

Accepted Answer

Osmosis is the net movement of water across a selectively permeable membrane from a region of lower solute concentration to higher solute concentration.

Question 8

Which of the following best describes an isotonic solution with respect to red blood cells?

Accepted Answer

An isotonic solution has the same osmolality as the cytoplasm, so there is no net movement of water.

Question 9

Which of the following is the correct Nernst equation for calculating the equilibrium potential ($$E_{ion}) $$for a monovalent cation at body temperature?

Accepted Answer

$$E_{ion} = \frac{61}{z} \log \left( \frac{[	ext{ion}]_{out}}{[	ext{ion}]_{in}} ight)$$

Question 10

A neuron has a resting membrane potential of -70 mV. Which of the following factors contribute most to this value?

Accepted Answer

The concentration gradient of K$$^+$$ and the selective permeability of the membrane to K$$^+$$ ions.

Question 11

Which of the following best describes a voltage-gated ion channel?

Accepted Answer

It opens in response to changes in membrane potential.

Question 12

If a cell is placed in a hypertonic solution, what will happen to the cell and why?

Accepted Answer

The cell will lose water and shrink because water moves out to the area of higher solute concentration.

Question 13

Which of the following is true regarding the osmolality of a 1 mol/L NaCl solution?

Accepted Answer

It is 2 Osm because NaCl dissociates into two particles: Na$$^+$$ and Cl$$^-.$$

Question 14

Which of the following best explains why plant cells do not burst in hypotonic solutions, while animal cells might?

Accepted Answer

Plant cells have rigid cell walls that prevent excessive swelling.

Question 15

A solution contains 180 g/L glucose and 180 g/L fructose. What is the osmolality of this solution?

Accepted Answer

2 Osm, because each sugar is 1 mol/L and both are non-electrolytes.

Question 16

Which of the following is a correct statement about ligand-gated ion channels?

Accepted Answer

They open in response to the binding of a specific molecule (ligand) to the channel.

Question 17

Which of the following best describes the direction of water movement during osmosis?

Accepted Answer

Water moves from an area of low solute concentration to an area of high solute concentration.

Question 18

Which of the following is the best definition of osmotic pressure?

Accepted Answer

The minimum pressure required to prevent the net movement of water across a semipermeable membrane.

Physio: Membrane Transport, Ion Channels, and Membrane Potential

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