BSC 114 Chapter Notes - Chapter 7: Plasmolysis, Osmoregulation, Pseudopodia
20 Sep 2016
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Plasma membrane exhibits selective permeability- it allows some substances to cross it more easily than others. Section 7. 1: cellular membranes are fluid mosaics of lipids and proteins. Lipids and proteins are the staple ingredients of membranes: most abundant lipids are phospholipids. Fluid mosaic model- the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids. Proteins are not randomly distributed in the membrane: often associated in long-lasting, specialized patches where they carry out common functions. Lipids appear to form defined regions as well. A membrane is held together primarily by hydrophobic interactions: most lipids and some of the proteins can shift about laterally. Adjacent phospholipids switch positions about 107 times per second. Proteins are much larger than lipids and move more slowly, but do drift. A membrane remains fluid as temperature decreases until the phospholipids settle into a closely packed arrangement and the membrane solidifies o. Cholesterol also hinders the close packing of phospholipids o.
