The Plasma Membrane Biology Fall 2017

Question How is a plasma membrane like a window screen? Each allows some things to pass through while keeping other things out.

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Definitions Plasma membrane- It is a flexible boundary of a cell that separates a cell from its surroundings. The plasma membrane regulates what enters and leaves the cell. It also provides extra protection and support. This is called selective permeability.

Selective Permeability 3 Rules to Selective Permeability Some molecules are allowed to pass through a plasma membrane at anytime. Other molecules are only allowed at certain times or in limited amounts. Some molecules are never allowed.

Structure of a Plasma Membrane Phospholipid bilayer- a double layered sheet that makes up nearly ALL plasma membranes. Phospholipid- made up of a glycerol, two fatty acids, and a phosphate group. Remember this? Lipid structure is a macromolecule which is made of a glycerol and a fatty acid.

Structure of a Plasma Membrane

Structure of the Plasma Membrane

Fluid Mosaic Model Plasma membranes contain protein molecules that are embedded in the phospholipid bilayer. Carbohydrate molecules are attached to many of the proteins. The organization of all these structures is called the fluid mosaic model.