Ch 7.2 Plasma Membrane
• Yesterday we talked about things all cells have.
One of those things was the plasma
membrane.
• Can you remember the other two?
• Lets review from yesterday
Two Basic Cell Types
Prokaryote
• no nucleus
• no organelles
• mostly unicellular
• very small in size
• ex. bacteria, archaebacteria
Eukaryote
• contains nucleus
• contains organelles
(membrane-bound structures
within cell)
• mostly multicellular
• ex. plants, animals, yeast
ALL cells have 1. plasma membrane
2. Ability to break down molcules
3. genetic material
• Plasma Membrane- a boundary that
controls what leaves and enters the
cell.
Why is it important to control
what leaves and enters the cell???
• All prokaryotes and eukaryotes have a plasma
membrane
• Surrounds the cell, providing protection and
support
• Helps a cell maintain homeostasis, by
regulating what enters and leaves the cell
• Selectively Permeable: Only allows certain
materials through
The plasma membrane has 4 main
components.
1.Phospholipid Bilayer
2.Transport proteins
3. Cholesterols
4.Carbohydrates
Structure of the Plasma Membrane
• The plasma membrane is composed of a
phospholipid bilayer – two layers of
phospholipids are arranged tail to tail.
Lipids – make up the lipid bilayer
a. Hydrophobic region
(between layers)
b. Hydrophilic region
(inside and outside the cell)
Hydrophilic = Water
Loving
Hydrophobic= Water
Fearing
Other Components of the Plasma
Membrane
Within the Phospholipids there are 3 other
things.
Do you remember????
• Transport proteins
• Cholesterols
• Carbohydrates
Other Components of the Plasma
Membrane
2. Transport proteins - create tunnels through
which certain substances enter and leave the
cell.
Other Components of the Plasma
Membrane
3. Cholesterols contribute to the fluidity of the
plasma membrane in that they prevent the
fatty-acid tails from sticking together.
Other Components of the Plasma
Membrane
4. Carbohydrates attached to proteins stick out
from the plasma membrane and help identify
the cell
It looks like this
Fluid Mosaic Model
• http://www.susanahalpine.com/anim/Life/me
mb.htm
• The components of the plasma membrane are
in constant motion sliding past each other.
• The phospholipids in the bilayer create a
“sea” in which other molecules can float,
hence “fluid” and “mosaic” because there
are many components which appear as a
pattern or a mosaic.
Ok what???
• Fluid mosaic model- All the parts of the
plasma membrane are moving all the time
Review/Study Questions
• How does the plasma membrane help
maintain homeostasis?
• What does it mean if something is selectively
permeable?
• What makes up the plasma membrane?
• Why are the phospholipids arranged like they
are?
Plasma Membrane Poster
On your BLANK PAPER complete the following:
1. Title: Plasma Membrane
2. Draw a plasma membrane in color (page 188!))
3. Label the:
* Phospholipids
* Proteins
* Carbohydrates
* Cholestrols
* Inside the cell
* Hydrophobic areas in BLUE (water fearing!)
* Hydrophilic areas in RED (water loving)
4. In the lower RIGHT corner, write your name
Questions on Back
– Define plasma membrane
– What is the plasma membranes function?
– Tell me what the cholesterol does
– Tell me what the transport protein does
– Tell me what the carbohydrate does