Review Questions

Which of the following best describes the structure of the cell membrane?
A) Rigid layer made only of proteins
B) Fluid mosaic of lipids, proteins, and carbohydrates
C) Solid double layer of phospholipids
D) Single layer of fatty acids

Fill in the blank: The cell membrane is described as __________ because it allows some substances to pass while restricting others.

What is the main difference between passive transport and active transport?

Which type of transport requires energy in the form of ATP?
A) Osmosis
B) Facilitated diffusion
C) Active transport
D) Simple diffusion

True or False: Diffusion always moves molecules from a region of high concentration to low concentration.

Match the type of transport (Column A) with the correct description (Column B):

• Column A

  1. Simple diffusion

  2. Facilitated diffusion

  3. Osmosis

  4. Active transport

  5. Endocytosis

• Column B
  A. Movement of water across a selectively permeable membrane
  B. Molecules move down concentration gradient with the help of proteins
  C. Movement of molecules against the concentration gradient using ATP
  D. Molecules move directly through the phospholipid bilayer
  E. Bulk transport of material into the cell via vesicles

In osmosis, water moves toward the solution with a __________ solute concentration.

Define isotonic, hypertonic, and hypotonic solutions.

A red blood cell placed in a hypertonic solution will:
A) Swell and burst
B) Shrink (crenate)
C) Remain the same size
D) Divide

Fill in the blank: Exocytosis is the process of transporting materials __________ the cell using vesicles.

What role do protein channels and carrier proteins play in facilitated diffusion?

Explain why active transport is necessary for cells, even though diffusion naturally moves molecules.

Which of the following is an example of active transport in cells?
A) Movement of oxygen across the membrane
B) Sodium-potassium pump
C) Diffusion of carbon dioxide
D) Osmosis of water into a plant root

Describe what happens to plant cells in hypotonic, isotonic, and hypertonic environments.

Short answer: Explain the fluid mosaic model and how it relates to the function of the cell membrane.