4.5 - Co-transport of Glucose in the Ileum

What are co-transporters? (1)

A specific type of carrier proteins that can bind to two molecules at once.

How do co-transporters work? (1)

They use the concentration gradient of one molecule to move the other molecule against its own concentration gradient

What are carbohydrates broken down into during digestion? (1)

Glucose

Where is glucose absorbed from and where does it go? (1)

Glucose is absorbed from the lumen of the small intestine and goes towards the bloodstream.

How is co-transport used for glucose? (1)

Glucose is absorbed from the intestines into the blood using co-transport.

The co-transport of glucose involves 3 different proteins. What are they? (3)

• Na+/K+ pump

• Sodium-glucose co-transporter proteins

• Glucose protein channels

State the first step of the process of the co-transport of sodium and glucose. (2)

• Na⁺ is actively transported out of epithelial cells into the blood by the sodium-potassium pump.

• So there is now a higher concentration of Na⁺ in the lumen than in the epithelial cells

There is a higher concentration of Na+ in the lumen than in the epithelial cell due to the Na+ being actively transported out the epithelial cell via the Na+/K+ pump. What occurs next? (3)

• Na⁺ diffuses from a high concentration in the lumen to a low concentration in the epithelial cells.

• It is transported via sodium-glucose co-transporter proteins, which also carry glucose molecules.

• Causing the concentration of glucose inside the epithelial cells to increase.

There is now a higher concentration of glucose inside the epithelial cells. What occurs next in co-transport?

• There is now a higher glucose concentration in the epithelial cells than in the blood

• So, glucose diffuses out of epithelial cells and into the blood via facilitated diffusion.

Why do glucose molecules move by co-transport rather than active transport into the bloodstream? (1)

Because glucose molecules are moved against their concentration gradient due to the Na⁺ concentration gradient, rather than by using ATP

Name one other organic compound which can be absorbed into the small intestine.

Amino acids;

What is ATP used for in the co-transport of Na+? (1)

Maintaining the concentration gradient of sodium ions between the lumen and the epithelial cells of the ileum