4.5 - Co-transport of Glucose

Question 1

why are glucose molecules moved against their concentration gradient?

Answer 1

• due to the Na+ conc gradient, uses co-transport than ATP and the same is used for absorption fo amino acids
• ATP is used to maintain the conc gradient of sodium ions between the lumen and the epithelial cells of the ileum

Question 2

Process of the co-transport of sodium and glucose

Answer 2

1. Na+ is actively transported out of epithelial cells into the blood by the sodium-potassium pump, transports 3 Na+ out for every two K+ in, creates a concentration gradient as there’s a higher conc of Na+ in the lumen than in the epithelial cells
2. Na+ diffuses from a high conc in the lumen to a low conc in the epithelial cells. It is transported via sodium-glucose co-transporter proteins, which also carry glucose molecules, causes the conc of glucose inside the epithelial cells to increase
3. There’s now a higher glucose conc. in the epithelial cells than in the blood, glucose diffuses out of epithelial cells and into the blood via facilitated diffusion

Question 3

What three proteins does co-transport involve?

Answer 3

• sodium-potassium pumps
  actively transports sodium and potassium ions
• sodium-glucose co-transporter proteins - use facilitated diffusion to transport Na+ ions and glucose molecules
• glucose protein channels - use facilitated diffusion to transport glucose molecules

Question 4

How is glucose absorbed in the small intestine and how are problems overcome?

Answer 4

carbohydrates are broken down into glucose in the small intestine and is absorbed into the bloodstream from the lumen
* to overcome isotonic solutions, co-transport is used

Question 5

what is co-transport?

Answer 5

• some carrier proteins can bind to two at once
• known as co-transporters

uses the conc gradient of one molecule
to move the other molecule against its own conc gradient