BI110 Lecture Notes - Lecture 8: Membrane Transport Protein, Facilitated Diffusion, Passive 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 chemical energy such as atp. Diffusion: net movement of a substance from region of higher to lower concentration: ex. The bigger the drop of food colouring, the faster the beaker fills with colour; Still requires energy, (cid:271)ut does(cid:374)"t use (cid:272)he(cid:373)i(cid:272)al e(cid:374)ergy fro(cid:373) atp. larger concentration gradient: concentration gradient itself is a form of potential energy, as the molecule moves from [high]>[low], it gives off this energy. Two things other than concentration gradient also effect diffusion rate: size of molecule. As size increases, rate of diffusion decreases: temperature. The bigger the gradient, the faster the diffusion rate. Diffusion will continue until concentration is the same on both sides of the membrane. It is at equilibrium there is still movement across the membrane, but at the same rate.
