PS101 Chapter Notes -Alpha Helix, Membrane Transport, Viscosity
Document Summary
Plasma membrane acts as a selectively permeable barrier that allows for the uptake of key nutrients and elimination of waste products while maintaining the protected environment for cellular processes to occur. A membrane consists of proteins in a fluid of lipid molecules. Fluid mosaic model is a model that shows that membranes are not ridged with molecules locked into place but rather consist of proteins within a mixture of lipid molecules. Lipid molecules exist in the bilayer [less than 10nm thick] Lipids in the membrane are very dynamic because they exchange places, vibrate, flex back and forth, move sideways and spin around their long axis. The proportions of lipid and protein within a membrane depends on the type of membrane. An important characteristic of membranes is that the proteins and other components of one half of the lipid bilayer are different from those that make up the other half of the bilayer.
