Download 3.2-Cell Membrane

Lesson #3.2Cell
Membrane
About the Cell (Plasma) Membrane…
• Purpose is to separate the
cell’s contents (inside of cell)
from the external environment
• It is present in ALL living things
o animals, plants, fungi, protists and bacteria
• Controls what enters and exits the cell
• It is used by the cell to take in
nutrients from the outside
environment and get rid of wastes
Structure of Membrane…
• The membrane is made of
lipids and proteins
• It is a double layer of
phospholipids, called a phospholipid bilayer
Structure of Membrane…
• The phospholipid is made up of
a phosphate group and a lipid
• The phosphate group is
hydrophilic (or polar), meaning it
mixes in water (water soluble)
• The lipid tails are hydrophobic
(or non-polar), they do not mix
in water (not water soluble
Water-loving
Water-hating
Structure of Membrane…
• The phosphate groups are on
the outside of the membrane,
that means they face the inside
of the cell and the outside of the cell
• The lipids are buried in the inner part of the
membrane and face each other
Structure of Membrane…
• Many different protein molecules
are found embedded in the cell
membrane
• Phospholipids make up most of the
structure; proteins carry most of the functions
Structure of Membrane…
• Many different protein molecules
are found embedded in the cell
membrane
• Integral proteins go right through the cell
membrane-from one side all the way to the
other side, peripheral proteins are found on only one
side of the membrane
Function of Membrane…
1. Transport
•
•
•
Some of the proteins embedded in
the membrane make it selectively
permeable = this means the proteins
(transport proteins) control which materials can enter
and leave the cell
Nutrients enter the cell
and wastes are removed
Ex. Na+/K+ pump
proteins in nerve cells
cause electrical signals to
flow along nerves
Function of Membrane…
2. Receptor Sites
•
•
Other membrane proteins bind specific
substances that control how the cell
functions these are receptor proteins
Ex. Insulin is a hormone that attaches itself to specific
receptor proteins embedded in the cell membrane, this
causes the protein to open and let sugar molecules
inside the cell
Function of Membrane…
3. Identity
•
Certain membrane proteins are used
to give cells their identity to the
immune system
Ex. ABO blood types  immune system recognizes
our own blood type, but attacks foreign blood types
•
•
This is why transplants are sometimes rejected
Activity and Homework
1.Read pages 47-49
–
Skip Liposomes and
Aquaculture
2.Answer questions on page 49
#1,2,5 (Homework check)
3.Start Cell Membrane and
Transport PACKAGE, only do
questions 1-6