Active and co-transport

Question 1

1. Describe active transport.

Answer 1

Active transport is the movement of molecules from an area of low concentration, to an area high concentration, through a partially permeable membrane using a carrier protein. It requires the hydrolysis of ATP to release energy, and cause a change of shape of the carrier protein.

Question 2

2. Compare and contrast facilitated diffusion and active transport.

Answer 2

Facilitated diffusion involves channel or carrier proteins whereas active transport only involves carrier proteins; Facilitated diffusion does not use ATP whereas active transport uses ATP; Facilitated diffusion takes place down a concentration gradient whereas active transport can occur against a concentration gradient.

Question 3

3. Explain why a respiratory inhibitor would stop the movement of molecules by active transport.

Answer 3

ATP is produced during respiration. If there is no respiration, there will be no ATP produced. Without the hydrolysis of ATP, carrier proteins will not change shape to move molecules against the concentration gradient.

Question 4

5. Describe co-transport.

Answer 4

Co-transport occurs when two different molecules need to be attached to a carrier protein for it to change shape and move the molecules across the plasma membrane. This may or may not be against a concentration gradient.

Question 4

4. What molecules can be moved via active transport?

Answer 4

norganic ions, large molecules such as glucose and amino acids.

Question 5

6. Describe the co-transport of glucose
   and amino acids in the epithelial cells of the ileum.

Answer 5

Na+ ions are actively transported out of the epithelial cell and enter blood; this requires a carrier protein and ATP Na+ conc. in cell is lower than in lumen of the ileum Na+ ions enter by facilitated diffusion down the concentration gradient; Glucose/amino acid is absorbed with Na+ ions against the glucose concentration gradient

Question 6

7. The sports drink contains sodium chloride. Sodium chloride increases uptake of glucose in the small intestine.
   Explain how.

Answer 6

Sodium ions and glucose absorbed by co-transport; Sodium ions removed from epithelial cell by active transport into blood; Maintains low concentration of sodium ions in epithelial cell; Sodium ions enter epithelial cells by facilitated diffusion taking glucose with them from small intestine; Glucose moved by facilitated diffusion into blood from epithelial cells;

Question 7

8. The addition of a respiratory inhibitor stops the absorption of amino acids. Explain why.

Answer 7

No ATP produced so no active transport; Sodium ions not moved into/out of cell; No concentration gradient for sodium to move into cell with amino acid;