BIOL 1201 Chapter : Lecture 9 Chapter 9 Respiration 2
Document Summary
The plasma membrane: the cell wall is mainly for structural support and protection. Movement of molecules requires two factors: there must be a concentration gradient. If there is a concentration gradient then the movement has a specific direction. Passive transport movement down a concentration gradient. Concentration gradient concentration change over a distance in a particular direction. Much of the movement of substances across membranes occurs by diffusion and therefore is a form of passive transport. Selective permeability the property of biological membranes which allows some substances to cross more easily than others. Two factors influence permeability: solubility characteristics of the substance crossing the membrane, facilitated diffusion by a carrier protein or a channel protein. Facilitated diffusion diffusion across a membrane with the help of protein. Types of facilitated diffusion: bind-and-release, selective channel, a pore the size of the solute, gated channel, like a selective channel only with a door. Osmosis the diffusion of water across a differently permeable membrane.
