1. Topic 3
Cell Membrane

2. Phospholipids Primary component of the cell membrane
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Phospholipids
Primary component of the cell membrane
Phosphate - Hydrophilic head
Fatty Acids - Hydrophobic tails

3. How do phospholipids interact with water?
   
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How do phospholipids interact with water?
Spontaneous formation!

4. Detailed view of an animal cell membrane
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Phospholipid

5. Cell Membrane – Structure and Function
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Cell membrane also called Plasma membrane
Phospholipids Bilayer
Main component of the cell membrane
Hydrophilic head points in and out
Hydrophobic tails
Carbohydrates
Cell to cell recognition
Extracellular
Connected to proteins and/or lipids
Glycoproteins
Glycolipids
Cholesterol
Imbedded into the phospholipid bilayer
Increases fluidity of membrane

6. Cell Membrane – Structure and Function (continued)
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Cell Membrane – Structure and Function (continued)
Proteins
Glycoproteins – cell to cell recognition
Important in immune system
Junctions between cells
Enzymes - imbedded in membrane
Receptors – trigger a chain reaction inside the cell
Transport proteins
Integrins – attach to cytoskeleton
Connect cells to cells or cells to the extracellular matrix

7. Cell membrane – TEM image
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Cell membrane – TEM image
Start here G block

8. Transmembrane protein or integral protein
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Transmembrane protein or integral protein
Spans the width of the bilayer
Often are transport proteins

9. Fluid Mosaic Model Phospholipids bilayer is in constant motion.
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Phospholipids bilayer is in constant motion.
Cholesterol - imbedded in membrane - adds to fluidity
Selectively permeable
Some molecules can pass though because of the fluidity

10. Cell membranes – “the gate keeper of the cell”
What does a cell need to bring in?
What does a cell need to get rid of?

11. Selective Permeability
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Only some substances can pass into the cell
What limits it?
Polarity of molecule
Size of molecule
Charge of molecule
Size
Passes freely through the membrane
Needs a special protein transporter
Needs to use other methods to pass through
Polarity and Size
Nonpolar molecules (steroids, N2, O2)
Some very small polar molecules (water, ethanol, etc)
Small polar molecules (amino acids, sugars, etc)
Large polar molecules (proteins)
Electric Charge
No charge
Charged atoms (H+ or Ca+)