1. The Cell Membrane

3. Cell membranes are composed of two phospholipid layers. (bilayer)
Phospholipids are composed of two different parts; a hydrophilic (“water loving”) head and two hydrophobic (“water fearing”) tails

5. The cell membrane has two major functions.
Forms a boundary between inside and outside of the cell
controls passage of materials
outside cell
cell membrane
inside cell

6. The fluid mosaic model describes the membrane.
With a partner, define the two words and discuss how this might relate to the cell membrane:
FLUID –
MOSAIC –
bendable, movable, not solid
made up of many pieces

7. The fluid mosaic model describes the membrane.

8. There are other molecules embedded in the membrane.
Proteins: help materials cross the membrane, relay messages, provide structure.
Carbohydrates: serve as identification tags
Cholesterol: strengthens the cell membrane
cell membrane
protein
cholesterol
carbohydrate
chain
protein channel

9. Some molecules can cross the membrane while others cannot.
The cell membrane is selectively permeable.
Some molecules can cross the membrane while others cannot.

10. Certain Molecules Can Cross The Membrane
Some molecules can cross through the membrane, while others cannot.
Those that cannot pass through the membrane must get into or out of the cell in other ways. Most of the time this involves proteins. Proteins can be used as:
channels to get molecules through
pumps that move the molecule across
receptors and transmit the signal across

12. Modeling the Cell Membrane Questions
How do the swabs represent the polar and nonpolar characteristics of the cell membrane?
What does the white pipe cleaner represent? What are these used for in the cell membrane?
What does the red pipe cleaner represent? What are these used for in the cell membrane?
What does the straw represent? What are these used for in the cell membrane?
In this model, the swabs and proteins can be moved around. Explain whether this is an accurate representation of actual cell membranes.