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Cell Membrane: Structure and
Function
The Plasma Membrane
• Cell membrane and nuclear membrane are
plasma membranes
• Semi-permeable
• Phospholipid bilayer with proteins
• Fluid-mosaic model
•
http://www.susanahalpine.com/anim/Life/memb.htm
Cell Membrane
• Phospholipid bilayer
Lipid
Phospho
Layer 1
Layer 2
Two layers = bilayer
Why bother with two layers?
Water loving (hydrophilic) outside
Water fearing (hydrophobic) inside
Fears water
Loves water
Layer 1
Layer 2
Membrane Proteins
1. Channel protein
2. Carrier protein
3. Cell recognition protein
4. Enzymatic protein
5. Receptor Protein
http://en.wikipedia.org/wiki/File:Fluid_Mosaic.svg
Transport Proteins
1) Channel or 2) Carrier
Channel Protein
Side View
Top down
When open allows sugars, salts, and amino
acids to pass
http://phet.colorado.edu/en/simulation/membrane-channels
DOI:10.2210/pdb2jqy/pdb
Receives a special molecule
Opens the closed gate
Extracellular End
Intracellular End
• Carrier Protein
10.2210/pdb2bg9/pdb
Channel vs. Carrier Proteins
Channel
Carrier
3) Cell Recognition Protein
What blood type
are you? A, B, AB or
O?
DOI:10.2210/pdb2edo/pdb
Extracellular
4) Enzymatic Proteins
Angiotensin II
Makes a molecule that
increases blood pressure
5) Membrane Proteins- Receptor Protein
Acetylcholine
Receptor
Extracellular
Intracellular
10.2210/pdb2bg9/pdb
Do you like to move
your muscles?
Summary
• Proteins play a large role in the function of
cells (therefore our lives)
• Different types of protein structures have
different functions
• Small examples given there are many
thousands of proteins in nature
• Tutorial/self-check:
http://www.bio.davidson.edu/people/macampbell/111/memb-swf/membranes.swf (link on homework
page)