Transcript The Three Major Parts of the Cell

Opening Questions:
st
1
1. What is the
major part of
the cell we talked about?
2. Name one thing that it does
for the cell.
3. Name the three types of
proteins that make up the
Cytoskeleton.
Learning Outcomes
Recognize the key components
of the cell plasma membrane.
Explain how the plasma
membrane regulates the
passage f molecules into and out
of the cell.
Describe the diverse functions of
proteins embedded in the palsma
membrane.
The Three Major
Parts of the Cell
2. PLASMA CELL
MEMBRANE
• It is the protective outer
covering of all cells
• It gives the cell its distinct
shape
• Acts as a fence around the cell
• Its like a PICKET FENCE
• Must stay in a SEMI-FLUID
state in order to be
• SEMI-PERMEABLE or
SELECTIVELY
PERMEABLE
SELECTIVELY or SEMI-PERMEABLE
• 1. Allows certain substances in
• Example---Nutrients
• 2. Allows certain substances out
• Example----Waste
• 3. Keeps certain things in
• Example----Organelles
• 4. Keeps certain things out
• Example---Disease and foreign
objects
A. 3 Molecules of the Cell
Membrane
1. PHOSPHOLIPID
MOLECULE
• Has a head that is made of
phosphate
• “Hydrophillic”
• Water loving
• Because it can dissolve in
water
• It has a tail that is made up
of a lipid
• “Hydrophobic”
• Water fearing
• Because it does not
dissolve in water
• Lipids will dissolve in other
lipids
• Because the tail is afraid of H2O and
there is H2O surrounding your
cells….
• Extracellular fluid outside each cell
and
• The cytoplasm (made of water and
various molecules) in each cell
• How do the phospholipid molecules
line up?
• They form a DOUBLE
layer with the tails facing
each other and the
heads on the outside and
inside.
• Phospholipid molecules
act as the pickets of the fence
• Little molecules can pass through
them by dissolving in lipids.
2. PROTEINS
Proteins are used to identify
large molecules or molecules
that can not dissolve in lipids.
Proteins decide whether the
larger molecules can come in
or not
2 TYPES OF PROTEINS:
1.Integral Proteins---Proteins that go all the way through the
membrane
2. Peripheral Proteins--Proteins that are only on one side of the
membrane
Proteins act as
the gate of the fence
MEMBRANE PROTEINS
a. Channel Proteins
b. Transport Proteins
c. Cell Recognition Proteins
d. Receptor Proteins
e. Enzymatic Proteins
f. Junction Proteins
A. CHANNEL PROTEINS
Channel Proteins form a tunnel
across the entire membrane…
They allow only one or a few
specific types of molecules to
enter or exit the cell.
EXAMPLE
Aquaporins--Channel proteins in the
kidney…
Allows water molecules in or
out of the cell
Without them we would
dehydrate
B. TRANSPORT PROTEINS
Transport Proteins often bond
with a molecule or ion and help
carry across the membrane.
They usually use cell energy to
help the molecule/ion across
EXAMPLE
They help sodium and
potassium to cross the
membrane of the nerve cell
(neuron)
Without them, nerve impulses
would be impossible.
C. CELL RECOGNITION
PROTEINS
Cell Recognition Proteins
are glycoproteins that are
used to enable our bodies
to distinguish between our
own cells and that of
another organism.
MORE INFO
Found especially on white
blood cells
Allow them to distinguish
between the pathogens that
invade our body and our own
cells
D. RECEPTOR
PROTEINS
Receptor Proteins are proteins
that change their shape
along the membrane which
allows a molecule known as
a SIGNAL MOLECULE to bind
to it.
The bonding of a signal
molecule causes the receptor
protein to change shape.
When the receptor protein
changes shape the cell is
able to respond to a certain
molecule.
EXAMPLE
Hormone insulin binds to the
receptor proteins in liver cells.
When they bind to the
membrane they allow the
liver cells to store glucose.
E. ENZYMATIC
PROTEINS
Enzymatic Proteins are
proteins that are directly
involved in the metabolic
processes of the cell.
These proteins can attach to
various cell membranes
EXAMPLE
DNA helicase--Enzyme that causes DNA to
unzip (break apart) so it can
replicate (duplicate)
F. JUNCTION
PROTEINS
Junction Proteins are
proteins will be discussed
later.
But they assist in cell to cell
adhesion and
communication
MORE INFO
The cells in the bladder use
junction proteins to adhere to
one another when the bladder
fills with liquid waste (urine).
3. CHOLESTEROL
• Another lipid
• Helps to give the cell
membrane its shape
Cholesterol acts as the posts of the
fence
3 major molecules(REVIEW)
• 1. PhosphoLIPID—
• Pickets—small things in & out
• 2. Proteins--• Gates---lets big things in & out
• 3. Cholesterol---LIPID
• Posts---structure
• The cell membrane is
considered a bilayer or a
DOUBLE layer of
• PROTEINS and
• LIPIDS
• Scientists way of
describing the cell
membrane
• The
Fluid
Mosaic
Model
• FLUID---Because the
membrane must stay semifluid to be selectively
permeable
• MOSAIC---Because it is
made up of many different
molecules but is one
structure
Wrap It Up
• The plasma cell membrane is
used as protection for each
cell--give it distinct shape
• It stays semi fluid---allowing it
to be selectively permeable
• This means it selects what
goes in and out and
• what stays in and out
• The plasma membrane is
made up of 3 main molecules:
• Phospholipid molecules
• Protein molecules and
• Cholesterol molecules
• For this reason the plasma
(cell) membrane is
considered a DOUBLE layer
of PROTEINS and LIPIDS.