1. Cell Membrane Structure

2. Proteins and Membranes
 Two main types of proteins are embedded in the cell membrane:
INTEGRAL PROTEINS
- penetrate the membrane
- transport specific molecules across the cell membrane
PERIPHERAL PROTEINS
- not embedded in the lipid bilayer
- are attached to the surface of lipids or exposed part of integral proteins
-gives the cell support

3. Other Parts of the Structure
Glycoprotein
Sugar and protein
Gives unique identification of the cell
Acts as a receptor for hormones and neurotransmitters
Helps stabilize membrane structure (with Glycolipids)
Glycolipid
Sugar and fat
Act as surface receptors (like glycoproteins)
Stabilize membrane structure

4. Glycoprotein and Glycolipid

5. Other Parts of the Structure
Cholesterol
Helps to stabilize the phospholipids by preventing their fatty acid tails from sticking together
Makes membrane less permeable
Makes cell membrane fluid in low temperatures
Makes cell membrane rigid in high temperatures
Helps regulate membrane fluidity
Important for membrane stability
Carbohydrates
On external surface of cell membrane
Used to identify cells of similarity

6. Cholesterol and Carbohydrates

7. How does the Cell Membrane Maintain Homeostasis?
Selective Permeability!
This is when a membrane allows some molecules to pass through while keeping others out.
(e.g. Screen Window – Air in, bugs out)
The hydrophobic core of the membrane prevents the transport of ions and polar molecules that are hydrophilic (water loving)

8. How Does the Cell Membrane Maintain Homeostasis?
The membrane is permeable to small molecules such as water, oxygen, and hydrocarbons
The membrane is impermeable to larger molecules such as glucose, and ions such as calcium ions or sodium ions – these must be allowed into the cell only at certain times, in certain amounts, and through certain channels.

9. Cell Membrane Coloring