Active and co-transport

Active transport

The active movement of substances against the concentration gradient using energy using specific carrier proteins. Only carrier proteins

How are molecules actively transported?

1. Complementary substance binds to specific carrier protein 2. ATP binds, hydrolysed into ADP + Pi, releasing energy 3. Carrier protein changes shape, releasing substance on side of higher concentration 4. Pi released → protein returns to original shape

Co-Transport

The transport of one substance coupled with the transport of another substance across a plasma membrane in the same direction through the same Co-Transporter protein

Example of Co-Transport

● Na + actively transported from epithelial cells to blood (by Na + /K + pump) ● Establishing a conc. gradient of Na + (higher in lumen than epithelial cell) 2 ● Na + enters epithelial cell down its concentration gradient with glucose against its concentration gradient ● Via a co-transporter protein 3 ● Glucose moves down a conc. gradient into blood via facilitated diffusion

Factors that affect active transport

1) Speed of individual carrier proteins

2) Number of carrier proteins present

3) Rate of respiration

Bulk transport

The transport of large amounts of molecules across the cell membrane which requires lots of ATP