Cell membrane: Fluid mosaic

What Are Characteristics Of The Cell Membrane? Selectively permeable Composed of –Lipids –Proteins

bi-layer of phospholipids Heads are polar hydrophilic –Tails are nonpolar hydrophobic Steroid molecules make membrane rigid. think: What do: “hydro” “philic” & “phobic” mean?

Lipids are fats & oils.Lipids are fats & oils. Lipids are composed of only C,H,O. Lipids are nonpolar. Lipids are composed of glycerol and 3 fatty acids. Macromolecules: Lipids The glycerol forms the “head” and The 3 fatty acid chains the “tails”

Has all single bonds in the fatty acid segment. Fatty acids are straight. Are solids at room temp. –animal fats. saturated fat Lipids: saturated fat Fatty acids

Have at least one double bond. –have bend. Are liquid at room temp –come from plants –Ex: olive oil. Unsaturated fats Lipids: Unsaturated fats Think: Which fatty acid would you expect to have a bent shape and where would the bend be?

Proteins embedded in bi-layer Peripheral proteins –act as recognition sites Integral proteins –act as channels Think: What do: “peripheral” & “integral” mean? How does this relate to where the proteins are in the plasma membrane?

Fluid Mosaic Model –Phospholipids move about. –Proteins move about. –Water keeps the membrane in position.

Review 1.Why do the lipids in the membrane have a polar and nonpolar end? 2.What do peripheral proteins do? 3.Why is the membrane “selectively” permeable?