Question 1

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

Accepted Answer

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

Question 2

Why are phospholipids considered amphipathic molecules?

Accepted Answer

They contain both a hydrophilic phosphate group and a hydrophobic fatty acid tail

Question 3

A scientist observes that water molecules cannot freely cross the plasma membrane. Which property of the membrane explains this observation?

Accepted Answer

The hydrophobic core of the phospholipid bilayer repels polar molecules like water

Question 4

Which of the following best explains why cells cannot grow indefinitely large?

Accepted Answer

As cells get bigger, their surface area to volume ratio decreases, limiting the rate at which materials can enter or leave the cell

Question 5

Which of the following molecules is most likely to diffuse rapidly across the plasma membrane without the help of a transport protein?

Accepted Answer

Oxygen ($$O_2)$$

Question 6

A cell is placed in a solution with a higher concentration of solutes than inside the cell. What will most likely happen to the cell due to diffusion?

Accepted Answer

Water will move out of the cell, causing it to shrink

Question 7

Which of the following statements about the function of the plasma membrane is correct?

Accepted Answer

It allows the cell to control what enters and leaves, maintaining internal concentrations of molecules

Question 8

Which of the following best describes the role of transport proteins in the plasma membrane?

Accepted Answer

They selectively allow specific molecules to cross the membrane that cannot pass through the lipid bilayer directly

Question 9

A mutation causes a cell to lack vesicles. Which process would be most directly affected?

Accepted Answer

Transport of large molecules or particles into and out of the cell

Question 10

If a cell's plasma membrane became permeable to all substances, what would be the most likely consequence?

Accepted Answer

The cell would lose its ability to maintain internal conditions different from the external environment

Question 11

Which of the following equations correctly represents the relationship between surface area and volume for a spherical cell?

Accepted Answer

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

Question 12

Which of the following best explains why diffusion is important for cell survival?

Accepted Answer

It allows for the passive movement of molecules, helping balance materials inside and outside the cell

Question 13

A cell is observed to have a high concentration of carbon dioxide ($$CO_2) $$inside and a low concentration outside. What will happen to $$CO_2$$ molecules?

Accepted Answer

$$CO_2$$ will diffuse out of the cell down its concentration gradient

Question 14

Which of the following is a direct consequence of a cell having a low surface area to volume ratio?

Accepted Answer

The cell will have difficulty efficiently exchanging materials with its environment

Question 15

Which of the following best describes the process of diffusion across a plasma membrane?

Accepted Answer

Molecules move from an area of higher concentration to an area of lower concentration without energy input

Question 16

Which of the following would most likely increase the rate at which oxygen diffuses into a cell?

Accepted Answer

Increasing the concentration of oxygen outside the cell

Question 17

Which of the following is NOT a function of the plasma membrane?

Accepted Answer

Synthesizing proteins for the cell

Question 18

Which of the following statements about vesicles is correct?

Accepted Answer

They are water-filled bubbles made of phospholipids that transport materials within or out of the cell

Question 19

Which of the following best explains why small nonpolar molecules can cross the plasma membrane more easily than large polar molecules?

Accepted Answer

The hydrophobic core of the membrane allows nonpolar molecules to pass, while polar molecules are repelled

Question 20

A patient is given an intravenous solution that is hypotonic to their blood cells. What is the most likely effect on the cells?

Accepted Answer

Water will enter the cells by osmosis, causing them to swell and possibly burst

Cell Membranes: Structure, Function, and Transport Mechanisms

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