Question 1

Which of the following best explains why phospholipids form bilayers in aqueous environments?

Accepted Answer

Phospholipids have both hydrophilic heads and hydrophobic tails, causing the heads to face water and the tails to avoid it.

Question 2

A cell is placed in a solution that is hypotonic to its cytoplasm. What is the most likely outcome for the cell?

Accepted Answer

Water will enter the cell, causing it to swell and possibly lyse.

Question 3

Which of the following statements about saturated and unsaturated fatty acids is correct?

Accepted Answer

Unsaturated fatty acids have at least one double bond, causing kinks in their structure.

Question 4

Which equation correctly represents the process of osmosis in terms of water potential ($$\Psi$$)?

Accepted Answer

$$\Psi = \Psi_s + \Psi_p$$

Question 5

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

Accepted Answer

Water will leave the cell, causing the cell membrane to pull away from the cell wall (plasmolysis).

Question 6

Which of the following best describes facilitated diffusion?

Accepted Answer

Passive movement of molecules down their concentration gradient via transport proteins.

Question 7

Which of the following molecules can most easily cross the plasma membrane without the help of transport proteins?

Accepted Answer

Small nonpolar molecules such as $$O_2$$ and $$CO_2.$$

Question 8

A researcher observes that a cell is using ATP to move sodium ions out of the cell and potassium ions into the cell. Which process is being observed?

Accepted Answer

Active transport via the sodium-potassium pump

Question 9

Which of the following is a major function of fats in animals?

Accepted Answer

Storing energy for long-term use

Question 10

Which statement best explains why cholesterol is important in animal cell membranes?

Accepted Answer

Cholesterol helps stabilize membrane fluidity, preventing it from becoming too rigid or too fluid.

Question 11

Which of the following best describes the fluid mosaic model of the plasma membrane?

Accepted Answer

A dynamic structure with proteins and lipids able to move laterally within the bilayer.

Question 12

Which process allows water to move rapidly across cell membranes in response to osmotic gradients?

Accepted Answer

Facilitated diffusion through aquaporins

Question 13

A cell is placed in an isotonic solution. What will happen to the cell?

Accepted Answer

There will be no net movement of water, and the cell will remain the same size.

Question 14

Which of the following is true about the movement of ions across the plasma membrane?

Accepted Answer

Ions require specific transport proteins to cross the membrane.

Question 15

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

Accepted Answer

Carrier proteins bind specific molecules and change shape to move them across the membrane.

Question 16

Which equation best represents the relationship between diffusion rate ($$J$$), membrane area ($$A$$), and concentration gradient ($$\Delta C$$)?

Accepted Answer

$$J = D 	imes A 	imes \Delta C$$

Question 17

Which of the following is a consequence of placing an animal cell in a hypertonic environment?

Accepted Answer

The cell will lose water and shrink (crenate).

Question 18

Which of the following statements about membrane proteins is correct?

Accepted Answer

Integral proteins span the membrane and are involved in transport and signaling.

Question 19

Which of the following best explains why unsaturated fatty acids increase membrane fluidity?

Accepted Answer

Their kinks prevent tight packing, allowing more movement of phospholipids.

Question 20

Which process is responsible for the movement of glucose into cells against its concentration gradient?

Accepted Answer

Active transport using ATP

Membrane Structure, Lipids, and Transport in General Biology

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