Osmosis in Cells

Study Notes

Cell membrane is semi-permeable, meaning it allows some substances to pass through while others cannot
Osmosis is the movement of water molecules across a semi-permeable membrane
Driven by differences in solute concentration, the net movement of water out of or into a cell produces a force known as osmotic pressure.
Isotonic solution: The concentration of solutes is the same inside and outside the cell, resulting in no net movement of water
Hypertonic solution: The concentration of solutes is higher outside the cell than inside, resulting in water moving out of the cell
Hypotonic solution: The concentration of solutes is lower outside the cell than inside, resulting in water moving into the cell
Animal cells may burst in hypotonic situations due to an increase in internal pressure as water moves into the cell
Plant cells are able to maintain their shape even in a hypotonic environment due to the rigid cell wall

Requires energy to move substances across the cell membrane, against their concentration gradient, from an area of low to high concentration
Protein pumps: integral membrane proteins that use energy, usually from ATP, to move molecules across the membrane against their concentration gradient
Endocytosis: process by which the cell takes in materials by engulfing them in a vesicle
Exocytosis: process by which the cell releases materials by fusing a vesicle with the cell membrane