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

PhosphoLipid

Layer 1 Layer 2

Two layers = bilayer

Why bother with two layers?Water loving (hydrophilic) outside Water fearing (hydrophobic) inside

Loves waterFears water

Layer 1 Layer 2

Membrane Proteins

1. Channel protein2. Carrier protein3. Cell recognition protein4. Enzymatic protein5. Receptor Protein

http://en.wikipedia.org/wiki/File:Fluid_Mosaic.svg

Transport Proteins1) Channel or 2) Carrier

Channel Protein

DOI:10.2210/pdb2jqy/pdb

Top down

Side View

When open allows sugars, salts, and amino acids to passhttp://phet.colorado.edu/en/simulation/membrane-channels

• Carrier Protein

10.2210/pdb2bg9/pdb

Extracellular End Intracellular End

Receives a special molecule Opens the closed gate

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

Extracellular

Intracellular

10.2210/pdb2bg9/pdb

Do you like to move your muscles?

Acetylcholine Receptor

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)