Cellular Transport

Functions of the cell membrane. 1. Provides boundary for cell 2. Selectively permeable- only allows certain things to pass through- “Picky” Ex. Window screen 3. Maintains homeostasis: balance within the cells

Relate the structure of the cell membrane to its function. Membrane is a lipid bilayer fluid-mosaic model Phospholipids: fatty areas that attract (hydrophillic) and repel (hydrophobic) water Embedded proteins: “bouncers” 1.Decide who goes in & out 2.Markers for recognition

Diffusion movement of particles from high to low concentration Ex. Perfume & Body odor OSMOSIS movement of water from high to low concentration. Both Go through bilayer Do NOT require cell energy (passive transport) Move until equilibrium is reached High concentration Low concentration Osmosis Diffusion

Cells in solutions.

Compare the three types of solutions. ISOTONIC: same strength particles outside = particles inside ISO- means “equal to” Movement into cell= movement out of cell

HYPOTONIC: concentration of dissolved substances is lower outside cell than inside cell HYPO means “below strength” Water will move INTO cell causing it to swell (it always moves to where there is more substances) Cells could rupture if the cell takes in too much water This increases pressure inside of cell (TURGOR PRESSURE)

HYPERTONIC: concentration of dissolved substances is higher outside the cell HYPER means “above strength” Water rushes OUT of cell causing it to shrivel (water rushes to where there is more substances) Can result in PLASMOLYSIS in plants which causes wilting

FACILITATED DIFFUSION: type of diffusion since movement is from high to low concentration, but this type goes through a protein channel rather than bilayer. Also Passive Transport Proteins –picky “bouncers” Glucose molecules Protein channel Low Concentration High Concentration

ACTIVE TRANSPORT: transport against concentration gradient; goes from low to high concentration Go through protein channel This requires energy to move them into cell; ex: Na-K pump Molecule to be carried Molecule being carried Energy Low Concentration High Concentration

Types of active transport: ENDOCYTOSIS: cells take in large clumps of substances Phagocytosis: “cell eating” take in food Pinocytosis: “cell drinking” take in water EXOCYTOSIS: cells move substances out(exit) ex: wastes

Summary Diffusion & Osmosis/ high to low conc./ go in between phospholipid spaces/ no energy= Passive transport Facilitated Diffusion- high to low/ no energy/ goes through protein Active transport- low to high conc./ requires energy/ goes through protein Ex. Party `1. Air coming into a window screen 2. Someone opens the door & you walk through (door represents protein) 2. Someone opens the door & you walk through (door represents protein) 3. someone goes through the back door that is already open *coming in=Endocytosis going out= Exocytosis