Active Transport

Question 1

Explain the different ways food molecules, such as glucose and amino acids, are absorbed from the small intestine.

Answer 1

If the concentration of the nutrients is lower in the intestinal wall cells/blood than in the small intestine then the food molecules move in by diffusion, down the concentration gradient.

If the concentration of the nutrients is higher in the intestinal wall cells/blood than in the small intestine then the food molecules move in by active transport, up the concentration gradient, using energy.

Question 2

How does active transport differ to diffusion and osmosis?

Answer 2

Active transport requires energy but diffusion and osmosis are passive processes (do not require energy).

Active transport requires carrier proteins to move substances across the membrane but diffusion and osmosis do not.

Question 2

How does osmosis differ to diffusion and active transport?

Answer 2

Osmosis only describes the movement of water but diffusion and active transport involve the movement of many different molecules.