Homeostasis and CellTransport Mr. Hamer's Halophiles

Transport through cell membranes The phospholipid bilayer is a great barrier around cells. However, for the cell to survive some materials need to be able to enter and leave the cell. There are 4 basic mechanisms: Diffusion Osmosis Facilitated diffusion Active transport

Diffusion of liquids

Diffusion is the net movement of substances from a region of their high concentration to a region of their lower concentration. The molecules move down a concentration gradient. As a result of diffusion, molecules reach equilibrium This is where they are evenly spread out, and there is no net movement of molecules from either side.

DIFFUSION Diffusion is a PASSIVE process which means no energy is used to make the molecules move.

Diffusion through a membrane Cell membrane Outside cell Inside cell

Diffusion through a membrane Cell membrane diffusion Outside cell Inside cell

Diffusion through a membrane Cell membrane Outside cell Inside cell EQUILIBRIUM

Molecules that diffuse through cell membranes Oxygen is non-polar so diffuses very quickly. Carbon dioxide is polar but very small so diffuses quickly. Water is polar but also very small so diffuses quickly.

Facilitated diffusion Large polar molecules like glucose and amino acids cannot diffuse across the membrane. These types of molecules pass through protein channels instead. This is called FACILITATED DIFFUSION.

Facilitated Diffusion through a membrane Cell membrane Protein channel Outside cell Inside cell

Facilitated Diffusion through a membrane Cell membrane diffusion Protein channel Outside cell Inside cell

Facilitated Diffusion through a membrane Cell membrane diffusion Protein channel Outside cell Inside cell EQUILIBRIUM

Facilitated diffusion

Osmosis The diffusion of water from an area of high concentration of water molecules to an area of low concentration of water across a selectively permeable membrane.

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

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

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