Cell Processes Transport

I. Transport Cell Membrane helps maintain homeostasis by regulating what substances enter and leave the cell

1. Passive Transport - movement of materials across a membrane which requires no cellular energy -Due to a difference in concentration- molecules move down concentration gradient

a. Diffusion - movement of materials from an area of high concentration to area of low concentration -may or may not include a membrane -only small, non-polar molecules diffuse through membrane

Driven by: kinetic energy Diffusion naturally leads to: equilibrium Equilibrium: when all the movement of molecules is equal

B. Osmosis -passive transport of water across a membrane from high concentration to low concentration 1.Hypertonic: Plasmolysis- shrinking of a cell from loss of water

2. Hypotonic: Cytolysis- swelling and bursting of a cell caused by internal pressure Turgor Pressure- pressure that builds up in a cell due to the inward flow of water

3. Isotonic:

C. Channel Proteins -Used when molecules have a charge (they would get stuck in middle) D. Facilitated Diffusion -Used when substances are too large to pass through -Diffusion through carrier proteins

Contrast Channel Protein vs. Facilitated Diffusion

2. Active Transport -Requires cellular energy ( ATP) -Sometimes the cell must move materials against their concentration gradient

a. Cell Membrane Pump -Uses carrier proteins to transport substances against the concentration gradient

B. Endocytosis -Ingestion of: fluid or macromoleucules -Two Types: Pinocytosis: cell drinking Phagocytosis: cell eating -Forms a vesicle from cell membrane Ex: White blood cell

c. Exocytosis -Vesicles in cytoplasm fuse with the membrane and release contents outside cell