1. Cell membrane: Fluid mosaic

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

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

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

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

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

7. 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?

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

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