Co Transport

Question 1

Describe how movement across membranes occurs by co-transport.

Answer 1

Two different substances bind to and move simultaneously via a co-transporter protein which is a type of carrier protein.
Movement of one substance against its concentration gradient is often couples with the movement of another down its concentration gradient.

Question 2

Describe the absorption of sodium ions and glucose by cells lining the ileum.

Answer 2

1)Na+ actively transported from epithelial cells to blood by Na+/K+ pump. This establishes a concentration gradient of Na+ which is higher in the lumen than the epithelial cell.
2)Na+ enters epithelial cell down its concentration gradient with glucose against its concentration gradient. This occurs via a co-transporter protein.
3)Glucose moves down a concentration gradient into blood via facilitated diffusion.