Question 1

Which of the following best explains why the phospholipid bilayer forms the basic structure of biological membranes?

Accepted Answer

Phospholipids have hydrophilic heads and hydrophobic tails, causing them to arrange in a bilayer with heads facing water and tails facing each other.

Question 2

A cell membrane is described as 'selectively permeable.' Which of the following molecules would most easily cross the membrane by simple diffusion?

Accepted Answer

Oxygen ($O_2$)

Question 3

Which factor would most likely increase the fluidity of a cell membrane?

Accepted Answer

Increasing the proportion of unsaturated fatty acids in phospholipids

Question 4

Peripheral membrane proteins differ from integral membrane proteins in that peripheral proteins:

Accepted Answer

Lack hydrophobic groups and are not embedded in the bilayer

Question 5

Which of the following best describes the fluid mosaic model of biological membranes?

Accepted Answer

A continuous phospholipid bilayer with proteins and carbohydrates floating and moving laterally

Question 6

Which of the following statements about membrane carbohydrates is correct?

Accepted Answer

They are located on the outer surface of the cell membrane and play a role in cell communication.

Question 7

Which of the following is NOT a way that molecules can cross the cell membrane?

Accepted Answer

Direct passage of large, hydrophilic molecules through the hydrophobic core

Question 8

Aquaporins are important for which cellular process?

Accepted Answer

Allowing large amounts of water to move across the membrane along its concentration gradient

Question 9

Which of the following would most likely decrease the rate of simple diffusion across a cell membrane?

Accepted Answer

Decreasing the temperature of the environment

Question 10

Which of the following is a correct real-world example of selective permeability in biological membranes?

Accepted Answer

A red blood cell allows $CO_2$ to diffuse out but restricts the movement of $Na^+$ ions.

Question 11

Which of the following best explains why ions such as $Na^+$ and $K^+$ cannot easily cross the phospholipid bilayer by simple diffusion?

Accepted Answer

They are hydrophilic and cannot dissolve in the hydrophobic interior of the membrane.

Question 12

Which of the following membrane components is most directly involved in cell-to-cell recognition and communication?

Accepted Answer

Membrane carbohydrates

Question 13

Which of the following is evidence supporting the endosymbiotic theory for the origin of mitochondria and chloroplasts?

Accepted Answer

They have double membranes and contain their own circular DNA similar to prokaryotes.

Question 14

A mutation causes a cell to produce phospholipids with longer, saturated fatty acid chains. What is the most likely effect on the cell membrane?

Accepted Answer

The membrane will become less fluid and more rigid.

Question 15

Which of the following best describes the role of cell walls in plant cells?

Accepted Answer

They provide a structural boundary and act as a permeability barrier for some substances.

Question 16

Which process is most directly responsible for the formation of the nucleus in early eukaryotic cells according to the endosymbiotic theory?

Accepted Answer

Loss of the cell wall and infolding of the plasma membrane

Question 17

Which of the following is a correct description of a glycolipid?

Accepted Answer

A lipid covalently bonded to a carbohydrate

Question 18

Which of the following would most likely restrict the movement of membrane proteins within the phospholipid bilayer?

Accepted Answer

Attachment to the cytoskeleton inside the cell

Question 19

Which pathway allows molecules to move between plant cells by passing through small holes in the cell wall?

Accepted Answer

Symplastic pathway via plasmodesmata

Cell Membranes: Structure, Function, and Origins

Study Guide - Practice Questions