1. The plasma membrane
Unit 2 – Homeostasis

2. What is the Plasma Membrane?
The membrane separates the organelles of the cell from the outside environment
It is made of a double layer of phospholipids and embedded proteins.

3. What does the plasma membrane do?
Controls what enters and leaves the cell.
Nutrients
Waste
It is said to be selectively permeable. (Everything CANNOT enter the cell)
Water can freely enter and leave the cell
Maintains homeostasis

4. What is the plasma Membrane made of?
Phosopholipids
Phosphate head
Lipid tail
Proteins
3 types

5. Structure of phosopholipids
Made of lipids (fats) with a phosphate head
Lipid portion is 2 fatty acid tails. The tail is hydrophobic: it does not interact well with water.
Phosphate head is hydrophilic: it can be exposed to a water environment.
phospholipid

6. Here is what a phospholipid bi- layer looks like as a sphere

7. How do materials move into and out of the cell?
Materials must move in and out of the cell through the plasma membrane.
Some materials move between the phospholipids.
Some materials move through the proteins.

8. How do materials move into and out of the cell?
Some proteins span membrane and determine which molecules can enter or leave. These are transport proteins.
Other proteins on the surface act as receptors.

9. The Proteins of the Plasma Membrane
Channel Proteins
Have channels that allow materials to move in and out.
Carrier Proteins
combine with a molecules to help them move
Enzymatic Proteins
Carry out metabolic reactions