Plasma Membrane and Cell Transport质膜与细胞运输.pptVIP

Diffusion All objects in motion have kinetic energy Particles of matter are in constant motion, colliding with one another Brownian Motion – random motion of atoms and molecules Characteristic of gases, liquids and some solids Particles of different substances in constant motion affect each other Diffusion Diffusion is the NET movement of particles from an area of high concentration to an area of lower concentration Diffusion is the result of Brownian motion Slow process Three key factors affect the rate of diffusion Concentration: more particles = more collisions Temperature: increased temp = increased particle movement decreased temp = decreased particle movement Pressure: Increased pressure accelerates particle motion and decreased pressure decelerates particle motion Results of Diffusion When dye is put into water, over time the dye and the water will be equally distributed There will be no change in the concentration of dye in the solution after equal distribution But the particles will continue to move This state of equal distribution with no change is concentration is called Dynamic Equilibrium Dye is the solute Water is the solvent Time Semipermeable Membrane Dynamic Equilibrium Diffusion in Living Systems Most substances are in water solutions in around cells with solute molecules equally distributed A Concentration Gradient exists when there is a difference in concentration of a substance across a space Ions and molecules diffuse from an area of high concentration to an area of lower concentration moving WITH the concentration gradient Diffusion requires no energy and is a type of passive transport Diffusion is one way substances move into out of cells Cell Transport and Osmosis Section 8.1 PLASMA MEMBRANE regulates what enters exits the cell Keeps the cell in HOMEOSTASIS The Plasma Membrane The Plasma Membrane The membrane is SELECTIVELY PERMEABLE Some materials enter and exit the cell freely Water, oxygen, etc… Other materials a