25 October, 2013
Facilitated water diffusion by Aquaporin:
- They are the channel protein that allows the diffusion of water across the
- Concentration gradient drives it.
- Water moves away from- hypotonic (lower concentration of solute)
- Water moves towards – hypertonic ( higher concentration of solute)
- Isotonic: no concentration. Net movement of water.
Tonicity and Osmotic water Movement:
- Hypotonic condition- lower concentration , moves to hypertonic- bag starts
- Hypotonic condition –higher concentration, start losing the water, bag
starts to shrink
- Isotonic condition- no concentration, bag is normal.
- (^^^) Another EX. Blood cell.
Active membrane transport
- ATP is needed in order to achieve the transport.
- Needs energy to move substance against their concentration gradient.
- Depends on membrane transport proteins
• Can be saturated
• (^^) Ex. Enzymes
2 kinds of Active Transport:
Primary active transport
- direct use of ATP
- Moves positively charged ions across membranes +
- Ex. Proton pumps. H
• Cells out of the cells
• Cells lining stomach
- Ca2+ pump
• Maintain low intracellular Ca2+ concentration
- Na+/ K+ pump