Cell Transport PDF

What determines what moves into & out of a cell? The PLASMA Membrane does! Outside Cell Inside the cell A plasma membrane is similar to a window screen…  Plasma membranes (P.M.) are picky! P.M.’s are selectively permeable...

What determines what moves into & out of a cell? The PLASMA Membrane does! Outside Cell Inside the cell A plasma membrane is similar to a window screen…  Plasma membranes (P.M.) are picky! P.M.’s are selectively permeable This means they only allow certain things to pass through P.M.’s help maintain homeostasis in the cell  What is homeostasis? Plasma membranes are primarily made of phospholipids + Polar Head w/ a charged phosphate group and a - glycerol I heart H2O! 2 Nonpolar Fatty acid tails I hate H2O! Ew! A Phospholipid Phosphate Head Fatty Acid Tail WATERY Chemistry Question – ARRGGHH! Which part of a phospholipid molecule faces the watery internal environment of a cell? A. Phosphate Head B. Fatty acid tails Is water polar or nonpolar? Is the phosphate head polar or nonpolar? Glycoprotein What determines which way substances flow?  Directionality of flow is determined by: - Concentration Gradient - Polarity - Size of molecules Cell’s Needs  Concentration Gradient: when one area has higher concentration of dissolved solute than another area Which side has more solute? Passive Transport – movement across a PM from high to low; no energy needed 3 Types: Simple diffusion, osmosis, facilitated diffusion Simple DIFFUSION: the movement from high concentration to low - This is called moving DOWN the concentration gradient Diffusion continues until equilibrium is reached - Equilibrium: when dissolved solutes are evenly spaced  Osmosis  The diffusion of water across a plasma membrane  High to low movement What is the difference between simple diffusion and osmosis?  3 Types of Solutions Isotonic: same concentration of dissolved stuff inside & outside cell; cell stays same size Hypertonic: more dissolved stuff outside cell; cell loses water to outside & shrinks Hypotonic: less dissolved stuff outside cell; cell gains water & swells Osmosis in Plant cells A cell is placed into a solution that has more dissolved solute than the inside of the cell. What type of solution is this: Hypertonic or Hypotonic?  Facilitated Diffusion  Diffusion through channels made of transport proteins in the plasma membrane  Transports ions, sugars, amino acids Phospholipids? Transport proteins? Blue circle? Active Transport – movement across membrane from LOW concentration to HIGH -Requires ENERGY (ATP)!! Carrier-mediated solute pumps: use protein channels to move solutes against gradient Ex. amino acids, some sugars, most ions LE 7-16 EXTRACELLULAR [Na+] high Na+ FLUID [K+] low Na+ Na+ Na+ Na+ Na+ Na+ Na+ [Na+] low ATP Na+ P P CYTOPLASM [K+] high ADP Cytoplasmic Na+ bonds to Na+ binding stimulates Phosphorylation causes the sodium-potassium pump phosphorylation by ATP. the protein to change its conformation, expelling Na+ to the outside. P P Extracellular K+ binds Loss of the phosphate K+ is released and Na+ to the protein, triggering restores the protein’s sites are receptive again; release of the phosphate original conformation. the cycle repeats. group. Sucrose cotransporter in plant cells Passive or Active Transport??  Endocytosis: moving large solutes or solutes in bulk into cell 1. Cell uses plasma membrane to enclose solutes w/in a vacuole 2. Digestion via what organelle? Phagocytosis (solid) – bacteria, dead cells Pinocytosis (liquid) – regularly occurs in cells that absorb Exocytosis – moving large solutes or solutes in bulk out of cell Solute-filled vesicle merges with PM & contents are released to outside cell