C190 Lecture Notes - Lecture 1: Facilitated Diffusion, Biological Membrane, Endocytosis
Document Summary
Simple diffusion is one molecule spontaneously move from areas of high concentration to areas of low concentration due to random movement. An example of this would be inc. dropped in water. Cells do not need carbon dioxide because it is a waste product to them. Nonpolar or polar and small molecules pass through the cell membrane easy. Water can easily pass through the cell membrane, but glucose cannot. The fatty acids side chains which are nonpolar are in the interior of the bilayer. Facilitated diffusion, is the process of helping molecules across a membrane using channels or pours. The movement of a substance across the biological membrane against a concentration, aided by specific transport proteins in requiring input of energy often as atp. Both simple and facilitated diffusion can be used to move a molecule down its concentration granite. When cells are large and polar, facilitated, diffusion, will be needed to move it down its concentration grandient.
