1. Cell Membrane Structure and Function
Goal: To be able to describe how the structure of the cell membrane regulates the flow of materials into/out of the cell.

2. Anatomy of a Cell Membrane

3. Phospholipid, Hydrophilic, hydrophobic, polar, nonpolar, phosphate, glycoprotein, protein

5. “Selectively Permeable”
perme = “allow”
A characteristic of cell membranes that allows it to regulate the passage of molecules
Selective permeability depends on the structure of the membrane
Not to be confused with semi-permeability
Dialysis tubing is semi-permeable. What characteristic allows molecules to travel through the membrane?
Our cell membranes are “selective” due to:
Proteins embedded within membrane
decide what can pass: big, small, necessary, unnecessary, charged, etc.
Properties of the phospholipids that make up the layer
Nonpolar, hydrophobic

6. Membrane Proteins
Some molecules may need “help” (of a protein) to get through the cell membrane, so require help from transport proteins:
Large molecules
Charged molecules or ions (Na+ or Cl- )
Molecules that may be traveling up their concentration gradient

7. Cross-Section of the Cell Membrane
Which molecules will allowed through the lipid bilayer and which ones may need the help of a protein?
H2O, CO2, Glucose (C6H12O6), Starch (lots of glucoses), Potassium (K+), estrogen, Na+
Why or why not?

8. Video Clip: Cell Membranes

9. Recap: Cell Membranes Characteristics: Selectively Permeable
Regulates what enters/exits cell
Helps transport certain molecules across with help of proteins
“Bilayered”
Hydrophobic
Hydrophilic
Embedded proteins (different functions)
Cell identification
Enzymes
Transport of molecules
Etc!

10. Interchangeable terms
Cell Membrane
Phospholipid Bilayer
Lipid Bilayer
Plasma Membrane
Fluid Mosaic Model

11. Types of Molecular Movement
high to low concentration
Diffusion
Passive Transport
Simple diffusion
Facilitated diffusion
Osmosis
Active Transport
high to low concentration
high to low concentration
high to low concentration
Requires energy by the cell “ATP”
low to high concentration
Requires a transport protein

12. Passive Transport Diffusion of solutes across a membrane
Simple Diffusion
Molecules can easily pass through the membrane
Molecule characteristics allow it to pass hydrophobic part of cell membrane
Diffusion = high  low concentration
Facilitated Diffusion
Molecules have to pass through membrane proteins to cross membrane
Molecule characteristics do not allow it to pass through hydrophobic part of cell membrane
Diffusion = high  low concentration

13. Active Transport Molecules pass through a protein to cross membrane
Not diffusion because active implies movement of solutes against their concentration gradient (i.e., low  high)
Being “active” requires energy!
Requires proteins or “pumps” to transport molecules across the membrane.
ATP

14. Video Clip: Active Transport

15. In Summary: Active Transport
Transport through a membrane
Requires energy (in the form of ATP)
Molecules move from low to high concentration

16. With your group, organize the following terms into the T-chart below and justify their placement there.
facilitated diffusion protein simple diffusion high  low concentration osmosis Energy low  high concentration requires a membrane ATP used
Passive Transport
Active Transport

17. Your Tasks Collect Day 2 data Clean Up: Homework due Monday
Solutions down sink
Cups rinsed and brought to cart up front
All containers rinsed and drying upside down
Homework due Monday
Analysis Questions

18. Homework due Tuesday? Learn About Cell Membranes! Worksheet
Interested in extra credit?
Learn about how soap works! Research micelle formation and explain, in words and using a few diagrams, how soap works and how this relates to what we learned today about the phospholipid bilayer. Submit typed response with diagrams tomorrow.