Q: A microbiologist discovers two new types of algae. Organism 1 is cubic (1.5 µm per side), and Organism 2 is rectangular (2 µm × 5 µm × 2 µm). Calculate the surface area to volume ratio for each organism. Which organism will have a greater challenge exchanging materials with its environment, and why?

Organism 1: $$\frac{6 \times (1.5)^2$}{(1.5)^3$} = 4$$; Organism 2: $$\frac{2(2 \times 5 + 2 \times 2 + 5 \times 2)}{2 \times 5 \times 2} = 1.4$$; Organism 2 will have more difficulty due to its lower surface area to volume ratio.

Question 1

A microbiologist discovers two new types of algae. Organism 1 is cubic (1.5 µm per side), and Organism 2 is rectangular (2 µm × 5 µm × 2 µm). Calculate the surface area to volume ratio for each organism. Which organism will have a greater challenge exchanging materials with its environment, and why?

Accepted Answer

Organism 1: $$\frac{6 	imes (1.5)^2$}{(1.5)^3$} = 4$$; Organism 2: $$\frac{2(2 	imes 5 + 2 	imes 2 + 5 	imes 2)}{2 	imes 5 	imes 2} = 1.4$$; Organism 2 will have more difficulty due to its lower surface area to volume ratio.

Question 2

Which of the following best describes the difference between simple diffusion and facilitated diffusion as shown in the rate vs. concentration graph?

Accepted Answer

Simple diffusion shows a linear increase in rate with concentration, while facilitated diffusion shows a hyperbolic increase that plateaus due to transporter saturation.

Question 3

A red blood cell is placed in a hypotonic solution. What will happen to the cell, and why?

Accepted Answer

The cell will lyse because water enters the cell by osmosis, causing it to swell and burst.

Question 4

Which of the following is an example of indirect active transport?

Accepted Answer

The Na$$^+/$$glucose symporter, which uses the Na$$^+$$ gradient to transport glucose against its concentration gradient.

Question 5

Which of the following best explains why plant cells become plasmolyzed in a hypertonic solution?

Accepted Answer

Water leaves the cell by osmosis, causing the plasma membrane to pull away from the cell wall.

Question 6

Which of the following statements about the Na$$^+/K$^+$$ ATPase is correct?

Accepted Answer

It moves 3 Na$$^+$$ ions out of the cell and 2 K$$^+$$ ions into the cell per ATP hydrolyzed.

Question 7

Which type of membrane transport protein is responsible for moving two different ions in opposite directions across the membrane?

Accepted Answer

Antiporter

Question 8

A patient with cystic fibrosis has a mutation in the CFTR protein. Which of the following best describes the consequence of this mutation?

Accepted Answer

Impaired chloride ion transport leads to thick, sticky mucus in the lungs.

Question 9

Which of the following best describes the function of V-type ATPases in cells?

Accepted Answer

They pump protons (H$$^+) $$into organelles like lysosomes and vacuoles, acidifying their interiors.

Question 10

Which of the following scenarios best illustrates osmosis?

Accepted Answer

Water moves from an area of low solute concentration to an area of high solute concentration across a semipermeable membrane.

Question 11

Which of the following is a characteristic of ligand-gated ion channels?

Accepted Answer

They open in response to the binding of a specific molecule, such as a neurotransmitter.

Question 12

A scientist uses the patch-clamp technique to study ion channels. What is the main advantage of this technique?

Accepted Answer

It allows the measurement of currents through individual ion channels in real time.

Question 13

Which of the following best describes the role of ATP in active transport?

Accepted Answer

ATP provides the energy required to move molecules against their concentration gradients.

Question 14

Which of the following is true about the movement of water in plant cells placed in a hypotonic solution?

Accepted Answer

Water enters the cell, making it turgid due to the cell wall preventing lysis.

Question 15

Which of the following best explains why facilitated diffusion reaches a maximum rate at high solute concentrations?

Accepted Answer

Transport proteins become saturated and cannot increase the rate further.

Question 16

Which of the following is a real-life example of a symporter in human physiology?

Accepted Answer

The Na$$^+/$$glucose cotransporter in the intestinal epithelium.

Question 17

Which of the following best describes the function of ABC transporters?

Accepted Answer

They use ATP hydrolysis to transport a wide variety of molecules across membranes.

Question 18

A neuron transmits a signal by opening voltage-gated Na$$^+$$ channels. What triggers these channels to open?

Accepted Answer

A change in membrane potential (voltage) across the membrane.

Question 19

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

Accepted Answer

Plant cells have a rigid cell wall that prevents lysis, while animal cells do not.

Membrane Transport and Osmosis: Mechanisms and Applications in Cell Biology

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