1. Cell Membranes (structure and function)
Why you don’t blow up like a balloon if you drink water
But also why you need to drink water

2. Essential Question:
How does the cell membrane’s structure allow it to maintain homeostasis?
Today we’re talking about the structure and function of the cell membrane.

3. Homeostasis Review
The ability to maintain a stable internal environment (even if the environment changes!)
Cell membranes are important in maintaining the correct level of fluids inside

4. Cell Membrane Structure (how it looks)
1. Phospholipid Bilayer
a) phosphate group head- Hydrophilic (loves water)
b) fatty acid tails- Hydrophobic (hates water!)
Remember: tails in, heads out
2. Cholesterol
a) gives the cell membrane strength
3. Proteins
a) Creates pores or channels to allow large molecules to pass through

5. Draw the structure of cell membranes in your notes

6. Cell Membrane Function (how/why it works)
Regulates what enters and leaves the cell
Maintains homeostasis because it is semi-permeable (only allowing certain materials to enter or exit)

7. Transport= Movement of materials or molecules across the membrane
Passive Transport (no energy required)= Movement of materials from HIGH to LOW concentrations
1. Diffusion= random movement of particles from high concentration to low concentration
Stops when equal on both sides
Ex. Osmosis- when WATER moves across the membrane
2. Facilitated Diffusion= movement from high to low concentration through a protein pore
When particles are TOO LARGE to pass through
Outside
Cell
membrane
Inside