A-Level Biology - Osmosis - Water Potential | Osmosis in Animal & Plant Cells (2027/28 exams)

Understanding Water Potential00:00:21

Water potential (psi) is the pressure exerted by water molecules in a solution. Pure water has a potential of zero kPa, and adding solutes makes the potential more negative. High water potential indicates a high water and low solute concentration, while low water potential indicates the opposite.

Definition and Process of Osmosis00:02:15

Osmosis is the diffusion of water across a partially permeable membrane from an area of higher water potential to an area of lower water potential. This movement continues until equilibrium is reached and net movement ceases.

Osmosis in Animal and Plant Cells00:03:27

Cells respond differently to solutions based on water potential. Hypotonic solutions cause animal cells to burst and plant cells to become turgid. Isotonic solutions keep cells stable. Hypertonic solutions cause animal cells to shrink and plant cells to become plasmolysed, leading to wilting.