IB Biology Topic B2.1.8: Selectivity in Membrane Permeability Notes

Selective Permeability: Cells Choose What Crosses the Membrane

1. The cell membrane maintains homeostasis by controlling what moves into and out of the cell.
2. Its selective permeability lets certain particles pass while blocking others, keeping the inside balanced.

Selectively Permeable Membranes Are More Precise Than Semi-Permeable Ones

1. Semi-permeable membranes
   1. They let small solutes through and are freely permeable to water.
   2. This describes artificial membranes such as those used in dialysis.
   3. They cannot control which specific substances cross.
2. Selectively permeable membranes