1. Ingenuity Honor’s Biology November 27th, Tuesday
Baltimore Polytechnic Institute
Ingenuity Honor’s Biology
November 27th, Tuesday
Unit 3: Cell membrane
Insong James Lee, Ph.D.

2. Unit 3: cell membrane November 27th, Tuesday Learning objectives:
What are the three macromolecule components of the cell membrane and what are their functions?
Describe the lipid bilayer structure of the cell membrane.
Explain what the fluid mosaic model is.
Discuss selective permeability of cell membranes.
Unit 3: cell membrane

3. Cell membrane Topic slides Brief review of macromolecules 4
(relevant to cell membrane).
2. Cell membrane overview
3. Phospholipids
Semi-permeability of cell membranes
Fluid mosaic model of membrane
Phospholipid differences in different
Organisms

4. Complete chart labeled “Do Now” on notes handout.
TASK:
Glycerol is a straight-chain carbohydrate with the formula C3H8O3. Draw its structure.
Complete chart labeled “Do Now” on notes handout.

5. Overview of cell membrane
slide 6

6. The Cell Membrane (aka Plasma Membrane)
Every cell has a membrane around it
Provides a boundary to the cell system
It selectively brings nutrients in and wastes out
Membranes are made of 3 types of molecules
LIPIDS
Proteins
Carbohydrates

7. Phospholipids
slides 8-12

8. Membrane Lipid = Phospholipid
YOU REMEMBER THE PHOSPHOLIPID RIGHT?
Polar Head
Two Nonpolar Tails

9. Let’s take another look:
HYDROPHILIC – loves water
HYDROPHOBIC – fears water

10. Water, Water Everywhere…
Ok, so we know that the cell membrane is made mainly of these phospholipids
We also know that there is water outside and inside of a cell
Question: How do the phospholipids arrange to create protective barrier for the cell?

11. A Bilayer!!!!
HYDROPHILIC
HYDROPHOBIC
HYDROPHILIC
Phospholipid Bilayer – two rows of phospholipids that surround every cell.

12. Put It All Together
Remember: The membrane is made of 3 major molecules, not only LIPIDS!

13. Semipermeability of cell membranes
slide 14

14. Semipermeability of cell membrane
The purpose of the external membrane of the cell is to allow only certain molecules to enter, while allowing wastes to exit:
Small non-polar molecules are the most likely to cross the membrane while large, polar molecules are the least likely.

15. Fluid mosaic model
slides 16-17

16. “Fluid Mosaic” Model

18. Differences in cell membrane in organisms
slides 19-23

19. Remember the three domains of life?
Bacteria and Archaea are domains of unicellular prokaryotes.
What’s so different about them anyway?

20. Ester and ethers
An ester is an organic compound where the hydrogen in the compound's carboxyl group is replaced with a hydrocarbon group. Esters are derived from carboxylic acids and (usually) an alcohol. While carboxylic acid has the -COOH group, the hydrogen is replaced by a hydrocarbon in an ester. The chemical formula of an ester takes the form RCO2R′, where R is the hydrocarbon parts of the carboxylic acid and R′ is the alcohol.
An ether is an organic compound that contains two alkyl or aryl groups by an oxygen atom. The general formula for an ether is R-O-R'.

21. One difference is the membrane lipids!
Unlike other organisms, archean cells use ether linked (-OH : -OH) lipids in their membranes. Also, the “tails” are funky.
Take home: archea have weird membrane lipids

22. The wonderful world of lipid chemistry

23. The Basics are as easy as 1. hydrophilic heads 2. hydrophobic tails 3
The Basics are as easy as 1. hydrophilic heads 2. hydrophobic tails 3. phospholipid bilayer!

24. Wrap Up Cell membrane structure: phospholipid bilayer
Cell membrane function: selective permeability controls what enters / exits cell
Time for a video? Inner Life of A Cell
Harvard U BioVisions computer modeling lab.