Question

which of the following is an example of facilitated diffusion?
glucose entering a cell with the help of the transport molecule insulin
oxygen passing through a cell membrane from a high concentration to a low concentration
all of these
potassium entering a cell via a special channel that requires energy

Explanation:

• Facilitated diffusion is a type of passive transport (no energy required) that uses transport proteins (channels or carriers) to move substances across the cell membrane down their concentration gradient.
• Glucose entering a cell with the help of the transport molecule (insulin is a hormone that signals the insertion of glucose transporters, which are transport proteins for glucose) is an example of facilitated diffusion as it uses a transport protein and moves down the concentration gradient (in a normal physiological context for glucose uptake in cells like muscle and fat cells).
• Oxygen passing through a cell membrane from a high concentration to a low concentration is simple diffusion (no transport protein involved).
• Potassium entering a cell via a special channel that requires energy is active transport (as it requires energy, which is not the case in facilitated diffusion).

Answer:

Glucose entering a cell with the help of the transport molecule insulin.