Transport through cell membranes

Transport through cell membranes The cell membrane is made of a phospholipid bilayer which allows certain molecules in and out of the cell We will discuss 2 basic mechanisms of transport: DIFFUSION OSMOSIS

Diffusion of liquids

Diffusion is the net movement of molecules from a region of their high concentration to a region of their lower concentration. The molecules move down a concentration gradient. Molecules continue until they reach equilibrium.

AS Biology, Cell membranes and Transport DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural kinetic energy. AS Biology, Cell membranes and Transport

5 Factors that affect diffusion Temperature- Higher temperature  diffuse faster Surface area- greater surface area diffuse faster Concentration gradient- Higher gradient  diffuse faster Size of particles- Smaller particles diffuse faster Diffusion Medium- Solid  slowest Liquid  faster Gas  fastest

Diffusion through a membrane Cell membrane Outside cell Inside cell AS Biology, Cell membranes and Transport

Diffusion through a membrane Cell membrane diffusion Outside cell Inside cell AS Biology, Cell membranes and Transport

Diffusion through a membrane Cell membrane Outside cell Inside cell EQUILIBRIUM AS Biology, Cell membranes and Transport

Osmosis ‘The diffusion of water from an area of high concentration of water molecules (high water potential) to an area of low concentration of water (low water potential) across a partially permeable membrane.

AS Biology, Cell membranes and Transport Osmosis CONCENTRATED SOLUTION DILUTE SOLUTION Cell membrane partially permeable. Sugar molecule VERY Low conc. of water molecules. High water potential. VERY High conc. of water molecules. High water potential. Outside cell Inside cell AS Biology, Cell membranes and Transport

AS Biology, Cell membranes and Transport Osmosis Cell membrane partially permeable. Low conc. of water molecules. High water potential. OSMOSIS High conc. of water molecules. High water potential. Outside cell Inside cell AS Biology, Cell membranes and Transport

AS Biology, Cell membranes and Transport Osmosis Cell membrane partially permeable. OSMOSIS Outside cell Inside cell EQUILIBRIUM. Equal water concentration on each side. Equal water potential has been reached. There is no net movement of water AS Biology, Cell membranes and Transport