Question 1

Which of the following best describes the structure of the plasma membrane in eukaryotic cells?

Accepted Answer

A double layer of phospholipids with hydrophilic heads facing outward and hydrophobic tails facing inward

Question 2

A red blood cell is placed in a solution and begins to swell and eventually bursts. Which term best describes the tonicity of the solution relative to the cell, and what is the direction of water movement?

Accepted Answer

The solution is hypotonic; water moves into the cell

Question 3

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It moves large or polar molecules down their concentration gradient with the help of specific membrane proteins

Question 4

During an experiment, dialysis tubing filled with a starch solution is placed in a beaker containing iodine. After 30 minutes, the inside of the tubing turns blue-black. What does this indicate about the movement of molecules?

Accepted Answer

Iodine diffused into the tubing and reacted with starch

Question 5

Which of the following factors would NOT increase the rate of simple diffusion across a plasma membrane?

Accepted Answer

Increasing the size of the diffusing molecule

Question 6

A cell uses the sodium-potassium pump to move sodium ions out and potassium ions in. Which process is this an example of, and why?

Accepted Answer

Active transport, because it requires ATP to move ions against their concentration gradients

Question 7

Why are cells generally small in size? Use the relationship between surface area and volume to support your answer.

Accepted Answer

Because as cells get larger, their volume increases faster than their surface area, making diffusion less efficient

Question 8

Which of the following best describes osmosis?

Accepted Answer

The movement of water from an area of low solute concentration to an area of high solute concentration

Question 9

A dialysis bag containing a 10% sucrose solution is placed in a beaker with a 40% sucrose solution. Predict what will happen to the bag over time and explain why.

Accepted Answer

The bag will lose water because water moves from low to high solute concentration

Question 10

Which component of the plasma membrane is primarily responsible for cell recognition and communication?

Accepted Answer

Carbohydrates

Question 11

If a cell is placed in an isotonic solution, what will happen to the cell's volume over time?

Accepted Answer

It will remain the same as water moves equally in and out

Question 12

Which of the following equations correctly represents the relationship between the surface area (SA) and volume (V) of a spherical cell with radius $$r$$?

Accepted Answer

$$SA = 4\pi r^2$ and V$$ = \frac{4}{3}\pi $$r^3$$

Question 13

Which of the following molecules is most likely to cross the plasma membrane by simple diffusion?

Accepted Answer

Oxygen ($$O_2)$$

Question 14

A scientist observes that chloride ions are present inside a dialysis bag after it was placed in a solution containing chloride ions. What does this observation suggest?

Accepted Answer

Chloride ions diffused into the bag through the semipermeable membrane

Question 15

Which process requires the direct use of ATP to move substances across the plasma membrane?

Accepted Answer

Active transport

Question 16

A cell is placed in a hypertonic solution. What will happen to the cell and why?

Accepted Answer

The cell will shrink as water leaves

Question 17

Which of the following best explains why large proteins cannot cross the plasma membrane by simple diffusion?

Accepted Answer

They are too large to pass through the phospholipid bilayer

Question 18

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

Accepted Answer

Absorption of glucose in the small intestine using sodium-glucose transport proteins

Question 19

If a cell's surface area is $$100\ \mu m^2$ and its volume is 50$$\ \mu $$m^3$$, what is its surface area to volume ratio?

Accepted Answer

$$2\ \mu m$$^{-1}$$

Question 20

Which of the following statements about the role of membrane proteins is correct?

Accepted Answer

They facilitate the movement of specific molecules across the membrane

Plasma Membrane Structure, Diffusion, Osmosis, and Cell Surface Area

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