Question

What is simple diffusion?
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3. Circle the statements below that would be TRUE about
simple diffusion. HINT: There is more than one!
A) It is a form of passive transport.
B) Molecules travel with the concentration gradient.
C) It is how glucose travels across the cell membrane.
D) It is how oxygen and carbon dioxide travel across the
membrane.
E) This transport is typical for large molecules.

Answer 1

**Simple diffusion** is the process by which molecules move from an area of higher concentration to an area of lower concentration without the need for energy input. This movement occurs directly across the cell membrane through lipid bilayers. Simple diffusion typically applies to small, nonpolar molecules, such as oxygen and carbon dioxide, that can easily pass through the hydrophobic regions of the membrane.

### True Statements About Simple Diffusion:
A) It is a form of passive transport.
B) Molecules travel with the concentration gradient.
D) It is how oxygen and carbon dioxide travel across the membrane.

### False Statements:
C) It is how glucose travels across the cell membrane. (Glucose typically requires facilitated diffusion as it is a larger, polar molecule.)
E) This transport is typical for large molecules. (Simple diffusion generally applies to small molecules, not large ones.)

So, the TRUE statements are A, B, and D.