1. Plasma Membrane – aka cell membrane
THE FLUID MOSAIC MODEL
Plasma Membrane – aka cell membrane
What is it?
What is it made of?
What is its function?

2. Cell Membrane Structure:
- A mosaic of lipids, proteins and carbohydrate, embedded in a fluid bilayer of phospholipids
Cell Membrane Function:
Controls what enters/exits a cell - maintains an internal balance called homeostasis
b. Provides protection and support for the cell

3. Structure of the Cell Membrane
Outside of cell
Carbohydrate
chains
Proteins
Lipid
Bilayer
Discuss integral and peripheral proteins
Transport
Protein
Phospholipids
Animations
of membrane structure
Inside of cell
(cytoplasm)
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4. Fluid Mosaic Model of the cell membrane
Polar heads love water
Membrane movement animation
Non-polar tails hide from water.
Carbohydrate cell markers
selective permeability of membrane – presence of pores
Proteins

5. HOW DOES THE MEMBRANE MOVE?
A membrane is held in together by weak hydrophobic interactions.
Most membrane lipids and some proteins can drift laterally within the membrane
Molecules rarely flip transversely (flip-flop) across the membrane, because hydrophilic parts would have to cross the membrane’s hydrophobic core.

6. Why is fluidity important?
Membrane must be fluid to work properly. Solidification may result in permeability changes
Unsaturated hydrocarbon tails enhance membrane fluidity because kinks at the carbon-to-carbon double bonds hinder close packing of phospholipids.

7. What else helps to keep membrane fluidity? Cholesterol
Cholesterol allows the cell membrane to stay fluid (esp. when
temp drops), while at the same time keeping the cell from
becoming too fluid (when temp rises) that it can no longer hold
its shape