BI110 Lecture 16: Module 18 - Membrane Transport
Document Summary
Hydrophobic nature of membranes restricts free movement of many molecules and substances essential for life. Passive transport movement of a substance across a membrane without need to expend (use) chemical energy such as atp. Passive transport can be driven by diffusion. Diffusion net movement of a substance from region of higher to lower concentration: for example dropping food colouring into a beaker of water. Bigger the concentration difference, the quicker the substances will diffuse to have equal amounts everywhere: concentration gradient is a form of potential energy. As molecule moves from high to low concentration areas, it is giving up energy. Simple diffusion passive transport of substances across the lipid portion of membranes with (or down) their concentration gradients (see diagram: small uncharged molecules move rapidly, larger or charged molecules may be strongly impeded from crossing membranes. Two compartments separated by a semi-permeable membrane. Membrane permeable to water but not to solute (sugar)
