Physiology 2130 Lecture Notes - Lecture 3: Facilitated Diffusion, Membrane Protein, Chemical Equilibrium
23 Sep 2015
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Document Summary
Proteins and transportation: one of the most important functions of proteins is to transport substances across the membrane, there are different ways in which transportation can occur through the cell membrane and its proteins, endocytosis and exocytosis (pinocytosis for small molecules). This involves the content of the vesicles (proteins) being released when the receptors on the vesicles bind to the membrane receptors. If the chemical and electrical gradients are in opposite directions the movement of the ion will depend on the balance of the two gradients and will stop when electrochemical equilibrium is achieved. Examples include sodium ions, potassium ions, and water molecules. Each protein channel is very specific (only allows one type of molecule). The rate of the movement of molecules across the membrane through protein channels are limited by several factors: 1) the size of the protein. The charge of the ion will affect the rate because the protein channels themselves also have charges.
