Cell Membrane

Membrane are NOT static Membranes are constantly: Forming Transforming Fusing Breaking Down

Photograph of a Cell Membrane ~ 8 nm thick

Cell Membrane The plasma membrane is flexible and allows a unicellular organism to move

Role of cell membrane Serves as a protective barrier Regulates transport (selectively permeable) Allows cell communication and recognition Cells have the ability to distinguish one type of neighboring cell from another This attribute is important in cell sorting and organization into tissues and organs in development

Cell Recognition Ability to distinguish one type of neighboring cell from another Important in cell sorting and organization into tissues This is the basis for rejection of foreign cells by immune system (ex. Human blood type) Cell recognize other cells by keying on surface molecules, often carbohydrates, on the plasma membrane.

Role of cell membrane cont. Bind cells together Contains the cytoplasm PROTEINS determine most of the membrane’s specific functions

Structure of the Cell Membrane

Structure of Cell Membrane

Fluid Mosaic Model of Membrane Structure Individual phospholipids and proteins can move around freely Mosaic The pattern produced by the scattered protein molecules when the membrane is viewed from above Fluidity Animation :47-1:20 seconds http://www.youtube.com/watch?v=nKgINP5QDIg&feature=related With narration

Lipid Bilayer Bilayer gives cell membranes a tough, flexible structure that forms a strong barrier between the cell and its surroundings

Cholesterol in membranes Membranes may be composed of up to 25% cholesterol Helps control cell membranes fluidity Restricts movement of tails Cholesterol Animation

Glycoproteins Proteins with attached carbohydrate chain Play an important role: in cellular recognition act as receptors for hormones

Proteins are critical to membrane function Proteins in the cell membrane help the cell interact with its environment Carry nutrients across cell membrane Receive chemical signals from outside the cell Act as an enzyme Anchor the cell in a location