4. osmosis and animal cells

WATER ENTERING

• water enters by osmosis

• cell swells up as solution inside cell/RBC has lower water potential than external solution

• eventually cell bursts (known as cell lysis or for RBC its haemolysis)

WATER LEAVING

• water lost from cell/RBC by osmosis

• the cytoplasm pulls away from cell membrane and cell/RBC becomes crinkled or crenated

OSMOTIC CONCENTRATIONS-HYPOTONIC

• means a lower conc

• a hypotonic solution has a lower conc of solutes compared to inside cell

• net movement of water would be into the cell

OSMOTIC CONCENTRATIONS- ISOTONIC

• means the same conc

• the conc of solutes in the solution is the same as the solute conc of the cell

• no net movement of water

OSMOTIC CONCENTRATIONS-HYPERTONIC

• means higher conc

• a hypertonic solution has a higher conc of solutes compared to inside cell

• net movement of water would be out of cell

WATER POTENTIAL IN ANIMAL CELL

• water potential in animal cells is simply the osmotic potential of the cytoplasm as there is no cell wall to exert a turgor pressure

• if water potential is diff between 2 regions that are separated by a partially permeable membrane, then water will move from the area of higher water potential to the area of lower water potential

• it would continue to move until the regions become isotonic or the cell bursts

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