Active Transport and Co-Transport

AQA A-Level Biology

Active Transport

Net movement of molecules / ions from an area of low concentration to an area of higher concentration. Requires ATP and carrier proteins.

Active Transport - Step 1

Ion binds to carrier protein on receptor sites

Active Transport - Step 2

On the inside of the membrane, ATP binds to the protein (and is then hydrolysed to form ADP and Pi)

Active Transport - Step 3

Causes protein to change shape and open to other side

Active Transport - Step 4

Ion is released

Active Transport - Step 5

Pi is released from protein, so it changes back to its original shape.

Co-Transport - Step 1

Sodium ions actively transported from ileum epithelium cell to blood by Na/K pump

Co-Transport - Step 2

Forms diffusion gradient for sodium to enter cells from gut (and with it, glucose)

Co-Transport - Step 3

Glucose enters by facilitated diffusion / co-transport with sodium ions