CELLULAR TRANSPORT What gets in and what gets out?

Passive Transport 1- Diffusion - occurs when there is an unequal concentration of molecules on one side of the cell compared to the other. The molecules move from the area of high concentration to an area of lower concentration until a dynamic equilibrium is reached. USED BY: Small Hydrophobic Molecules: O 2,CO 2, N 2 activity

Diffusion

Passive Transport 2 – Osmosis - the diffusion of water through a selectively permeable membrane. The membrane is permeable to water, but impermeable to the larger molecules. Water diffuses from an area of high water concentration to an area of lower water concentration until the equilibrium between water and solute is reached. USED BY: H 2 O demo

Passive Transport 3 - Facilitated diffusion – Gatekeeper proteins open and close paths through the cell membrane allowing some molecules to pass freely. It allows materials to move in and out of the cell much more quickly than regular diffusion and does not require energy from the cell. USED BY: Glucose. Diffuses into red blood cells faster than other similar sugars.

Active Transport The movement of materials from an area of lower concentration to an area of higher concentration by expending energy is called active transport. Carrier proteins receive energy that allows them to aid in active transport.

Active Transport 1 – Transport Carrier Proteins – Proteins open and close paths through the cell membrane allowing some small solutes to pass through. Energy is required to transport the solutes against the concentration gradient. USED BY: Sodium-potassium pump

Animation and quiz pter2/animation__how_the_sodium_potassium_pump_works.html

Active Transport 2 – Endocytosis – the process by which cells ingest materials. Large molecules can not pass through the cell membrane. The particle pushes against the membrane and forms an indentation. The cell membrane wraps around the particle and engulfs it into a vacuole. Often enzymes from lysosomes are then used to digest the molecules.

Active Transport 2a – Pinocytosis – the process of engulfing dissolved molecules. USED BY: fat droplets engulfed by cells of the small intestine

Active Transport 2b – Phagocytosis – the process of engulfing solid particles. Can be used to engulf whole cells. USED BY: invading microbes engulfed by white blood cells

Active Transport 3 – Exocytosis – the process by which large molecules in the cell are transported to the external environment. Materials are contained in vesicles. The vesicles fuse with the membrane and then the material is released. USED BY: waste materials released from the cell. Transmitter chemicals emitted from nerve cells.

Organizer Make a chart to organize the following key terms: –Cellular transport –Diffusion –Osmosis –Facilitated diffusion –Active transport –Endocytosis –Transporters –Passive transport –Exocytosis

Questions 1.Why are cell membranes a “bilayer”? 2.Why are proteins important for the functioning of a cell? Provide examples 3.Why are cells so small? 4.Compare and contrast: –Passive Active transport –Diffusion Facilitated Diffusion –Diffusion and Osmosis 5.Why must tissues used in medical procedures be bathed in a solution of the same osmolarity as the cytoplasm?

Reference images 1-osmosis.htmhttp://faculty.southwest.tn.edu/rburkett/GB 1-osmosis.htm