Bio 100 EXAM 2 STUDY GUIDE

CH 5 THE WORKING CELL

1. Properties of plasma membranes – fluid mosaic a. Lipids do what –Make up the phospholipid bilayer b. Proteins do what –embedded in lipid bilayer. Transports molecules across the membrane 2. Diffusion – movement down concentration gradient – Molecules move from HIGH concentration to LOW concentration until equilibrium is achieved 3. Passive transport/simple diffusion – diffusion across membrane. Needs no energy, energy comes from concentration gradient. c. Small molecules such as? –O2, CO2, Estrogen, Testosterone 4. Osmosis – water down concentration gradient – If there is a solute on both sides of a membrane but it is not permeable to the solute, water will move until the solute concentration is equal on both sides. 5. Tonicity – effects of hypotonic (LOW TONICITY) and hypertonic (HIGH TONICITY) solutions on cells - if solute outside or inside cell cannot cross membrane, osmosis occurs. When there is more of a solute inside a cell (hypotonic environment), osmosis occurs and water goes INTO the cell, the cell then explodes because of too much water. When there are less solutes inside a cell (hypertonic environment), water goes OUT of the cell and the cell shrinks.

6. Facilitated diffusion – (type of passive transport & relies on transport proteins) d. Transport proteins (embedded in lipid membrane) Form hydrophilic tunnels or they bind their passenger, change shape, and release them on the other side. (Are SPECIFIC for their substrates, which can be sugars, amino acids, ions, water) e. Polar or charged substances –what is transported using this f. Example aquaporin transports water – AQUAPORIN is a transport protein for WATER, when diffusion is slow (H20 is polar) 7. Active transport – ( NOT diffusion) Cell NEEDS energy, ATP. Moves a