Download Components of a Cell Membrane

Components of a Cell Membrane
(and all other membranes that surround the organelles)
Each organelle in a eukaryotic cell, is
surrounded by its own membrane (hence
the term “membrane-bound” organelles)
The individual membranes are not all
identical but they have many of the same
components.
Cell Membrane
• The entire cell is surrounded by a thin
membrane.
• Cell membrane is considered selectively
permeable.
• Q: What does this mean?
• A: Some things can pass through with ease,
others need some help, and some cannot
pass through at all.
• The cell membrane is not rigid; it is fluid (or
flexible) in its movement.
• The more unsaturated fatty acids chains more
fluidity the membrane has.
• The C.M. is also a mosaic. What
does “mosaic” mean?
• Its made up of many individual
parts; many parts making a whole.
The structure of the cell membrane is known
as the:
Components of a Cell
Membrane
1. Lipid Bilayer
2. Proteins: Peripheral and Integral
(A. channel, B. carrier, C. anchoring, D. marker proteins)
3. Structural Fibers
4. Exterior Proteins and Glycolipids
Phospholipids
• Cell membrane contains
Phospholipids
• Phospholipids contain a Polar
Head and a Non polar tail
• What does this mean?
• The “head” of the phospholipid
is hydrophilic and the “tails” are
hydrophobic.
These phospholipids are arranged in
2 layers making a lipid bilayer
Components of a Cell Membrane
1. Lipid Bilayer: two layers of lipids
Head-philic
Tail- phobic
-Long carbon chain
-can be saturated or unsaturated
Lipid Bilayer
•Polar heads are on the outside and the inside of
the cell.
•Non-polar tails make up the inside of the cell
membrane
•This forms a lipid bilayer
Components of a Cell Membrane
• 2. Proteins –Peripheral and Integral: (channel, carrier,
anchoring, marker proteins) proteins that float on or embedded
into the lipid bilayer.
Peripheral proteins – located both on the interior surface and the
exterior surface of the membrane. (receptor proteins)
Integral proteins- embedded in the lipid bilayer part of the protein
that extends through the bilayer.
These proteins allow certain organic compounds to cross the cell
membrane through: channels, pores, hydrophobic interactions
The Typical Cell Membrane
• is actually made up of two very different types of
membranes:
• 1) The passive phospholipid part (75-95%) and
• 2) the active protein part (5-25%).
• Those cells that have to do more exchanging of
materials, such as glandular cells, have more of the
protein membrane.
• Those cells that have minimal exchange of materials,
such as fat cells, have less protein membrane.
• The protein part of the cell membrane provides:
communication, "I.D." tags, anchors to microtubules,
gates of exchange for large molecules and pumps for
maintaining ionic balance.
Types of Proteins Found in Cell Membrane
Integral proteins:
A. Channel Proteins~ it is like a tunnel that allows
molecules to freely cross the cell
membrane.
B. Carrier (Transport) Proteins
•Carrier proteins are specific
•Selectively interacts with a specific
molecule or ion so that it can cross the
membrane
•After specific molecule/ion attaches
protein goes through a conformational
change. (changes shape)
•Carrier proteins help move molecules that
are NOT lipid soluble : Amino Acids,
Glucose
Carrier protein
C. Anchoring Proteins
1. Microfilaments: extend through the
cytoskeleton, anchoring peripheral
proteins to the cell membrane
2. Microtubules: bundles of
microfilaments making a strong
structure.
Ex. Red Blood cell- spectrin.
Length of one cable: 7,650 feet
Diameter of one cable: 36 3/6 inches
Wires in each cable: 27,572
Total wire used: 80,000 miles
Weight of cable (suspenders and
accessories): 24,500 tons
The main span is 4,200 feet
D. Marker Proteins
• a.k.a. Cell Recognition
Proteins
•Are shaped in such a way
that a specific molecule can
bind to it.
•This evokes a response
inside the cell
-“many signals to listen to,
but the cell knows which
signal to respond to”
(Like listening to one person
when 3 are speaking)
How Marker (receptor) Proteins Work:
Each receptor protein has a 3-dimensonal
shape that fits the shape of a specific
molecule
1. Signal molecule of right shape approaches
the receptor protein, the two bind
together.
2. Changes shape of protein producing a
response in the cell.
3. The cell responds to the signal molecules
that fit the particular set of receptor
proteins it possesses. It ignores other
signals.
Various Protein Types
Marker protein
Who’s Who in the Cell Membrane
• Receptor Protein: Informers of the cell. They gather info. about the
environment around the cell and sends messages to the nucleus.
• Channel Protein: acts like an alleyway, transporting substances into
and out of the cell.
• Marker Protein: “Name Tag” of the cell; Identifies what kind of cell
it is. “Hi, I’m a Liver Cell ”
• Gated Channel Protein: acts like a gate, controlling which
substances go into and out of the cell.
• Carbohydrate group: a “surface marker” which IDs the cell as
YOURS rather than an invaders. “I belong to Mrs. Pires”
• Cytoskeleton: supports the cell membrane
• Transport (Carrier) Proteins: Help molecules pass through the cell
membrane.
• Glycoproteins: have structural functions; can form connective
tissues such as collagen, also forms mucus secretions.
• Cholesterol: helps prevent extremes-- whether too fluid, or too
firm-- in the consistency of the cell membrane.
http://www.youtube.com/watch?v=Qqsf_UJcfBc
3. Structural Fibers
• Cytoskeletal elements (matrix) that interact
with the proteins in the cell and influence
cell shape and motility.
4. Glycoconjugates (Glycoproteins and Glycolipids):
-Act as receptors on cell surfaces that bring
other cells and proteins (collagen) together
giving strength and support to a matrix.
-work with Immune cells to attract bacteria to
these sites, bind them, and then destroy them..
- vary between species to species, individual to
individual, even from cell to cell within an
individual.
of glycoconjugates
-Each cell developsTypes
its own
type and pattern of
chain + protein =
glycoproteins and1.Sugar
glycolipids.
glycoprotein
2.Sugar chain + lipid = glycolipid
3.Extremely long sugar chains
(glycosaminoglycan) + protein =
proteoglycan
-The carbohydrate chains extending from the
glycolipids and glycoproteins serve as
“fingerprints” of the cell
-Many different variations of sugar chains
-Branched
-Immune system is able to recognize that the foreign tissue’s
cells do not have the same glycolipids/proteins as the rest of
the body. The immune system will attack the newly received
transplant. This is called transplant rejection.
To succeed, an individual has to take anti-rejection medication
usually for the rest of their life.
These medications suppress the Immune system, weakens it,
but doesn’t destroy all of the T and B cells. The body can still
can fight off most infections.
Cons of medication: People who take immunosuppressive drugs are
more likely to develop diabetes, kidney disease, infections and cancer.
Pros of medication: They get to live!
Successful Transplants
Face Transplants
The recipient of the world's first partial face transplant was a 38-yearold Frenchwoman named Isabelle Dinoire.
In May 2005, Dinoire took sleeping pills and passed out on her
couch. When she awoke and tried to light a cigarette, she was
surprised to find that it would not stay between her lips. A glance in
the mirror revealed a horrible sight -- Dinoire's black Labrador had
chewed off the lower part of her face, including her chin, lips and
much of her nose, leaving her teeth and gums completely exposed.
The donor was a
46-year-old woman
who had been left
brain dead from a
suicide attempt.
Bear Attack:
Do Now!
1. What does it mean to be selectively permeable?
2. Why is the cell membrane described as a fluid mosaic
model?
3. What is the difference between peripheral and Integral
proteins?
4. Draw a phospholipid and label the hydrophobic and
hydrophillic parts.
5. Why would a transplanted organ be rejected?
Cell Membrane and Its parts
7.3 Cell Transport (& Homeostasis)
Two Main Types of Transport
Passive Transport:
Does not need energy
Active Transport:
Needs energy
Like floating down a river, passive transport does
NOT need energy to occur
Passive
Transport
Diffusion – molecules move across a given space
without the use of energy from high
concentration to low concentration until
equilibrium is reached.
Osmosis - specifically water moving across a
membrane without the use of energy from HC
LC until equilibrium is reached.
Facilitated Transport- No energy, “help” moving
from HC LC (channel, carrier proteins) until
equilibrium is reached.
Solute concentration –particles inside and outside
the cell, effecting whether water moves INTO the cell,
or OUT of the cell.
More solutes means less room for water
(hypertonic solution)
Less Solutes More room for water
Osmosis : Three solutions
Water will move from an area of high concentration
to an area of low concentration
1. Hypotonic –water moves into the cell (cell
can “pop”) Example: Distilled water
Cytolysis – cell burst
2. Isotonic – no movement; equal
concentration of water on each side of the
membrane. Ex. Tap water, spring water,
purified water
3. Hypertonic – water moves out of the cell
(cell shrinks- called plasmolysis) Ex. Salt
water,
sugar water.
http://www.youtube.com/watch?v=gWkcFU-hHUk
Plant cell
Watering a Plant
(Think of blowing up a balloon)
Turgor Pressure: The pressure that
water molecules exert against the cell
wall is Turgor Pressure.
Plasmolysis- Cell shrinks away from
the cell wall, turgor pressure is lost.
Plant begins to Wilt
http://www.youtube.com/watch?v=GOxouJUt
EhE&feature=related
Plant plasmolysis: Cell Collapse due
to water loss
• Elodea:
• http://www.youtube.com/watch?v=JaCCKP
yE6I4&feature=related
• Onion
• http://www.youtube.com/watch?v=gYbt7hh
IxPo&feature=related
Diffusion/Osmosis Lab
•
•
•
•
Elodea in 3 different solutions.
Red onion in 3 different solutions.
Potato: Guess the solution
Dialysis tubing (starch baggy in iodine)
Important!
Cytoplasmic streaming:
http://www.youtube.com/
watch?v=8edk6nGMwMs
Order of solutions:
1) isotonic
2) hypertonic
3) hypotonic
Bio
Rocks!
(3 types)
Like paddling upstream,
active transport requires a lot
of energy!
I. ExocytosisDischarge of
materials from
vesicles at the cell
surface.
Animal cells- provide a mechanism for secreting
many hormones, neurotransmitters, digestive
enzymes and other substances.
What is the difference between a secretion and an excretion?
II. Endocytosisprocess the plasma
membrane extends
outward and
envelops food
particles.
A. Pinocytosis:cell
drinking
B. Phagocytosis: cell
eating
http://www.youtube.com/watch?v=4 http://www.youtube.com/watch?v=
gLtk8Yc1Zc&NR=1
UeuL3HPfeQw&feature=related
• “melt” into
your cells
through the
lipid bilayer
even if your
cell do not
want the
substance.
Ex. Alcohol and Ether
Particles can move independent of the
concentration gradient by using “pumps”
within the cell membrane.
Cells that perform a lot of active
transport, require a lot of mitochondria.
Ex. Nerve and Muscle cells (both perform
a lot of active transport)
• Almost all of the active transport in animal
cells is carried out by only two kinds of
pumps:
1. The sodium-potassium pump and
2. The proton pumps.
1/3 of the body’s energy is
used to work this pump!
Background info to understand
sodium potassium pump
The cell’s energy is in
the form of ATP
When the cell needs energy, it breaks
off a P and the high energy is
released for active transport.
Sodium (Na) can have a
positive charge (Na+) and
potassium K+ will be
positive too
Na+/K+ pump: Very Important !
1. Carrier protein has a shape that allows 3 Na + to enter
2. ATP (energy) splits, phosphate attaches to carrier (split
by enzyme in carrier)
3. Change in shape allows 3 Na +’s to be dumped outside
cell
4. New Shape allows 2 K+’s to enter carrier protein
5. Phosphate group is released (conformational change)
6. Carrier protein changes back to original shape,
releasing 2 K +’s inside the cell.
http://www.you
tube.com/watch
?v=9CBoBewd
S3U
Na+/K+ pump continued
Pump results in concentration gradient and electrical
gradient across the cell.
3 Na+’s outside cell, 2 K+ inside cell.
Outside is more positive than the inside of the cell.
Na+ via diffusion, 300 Na per sec per carrier
Animation:
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__ho
w_the_sodium_potassium_pump_works.html
How does so much Na+ get in the cell
(and K+ out of the cell) in the first place?_
Cl- is electrically attracted to Na+ and follows it by
flowing through CFTR Cl- channels allowing
reabsorption of salt in excess of water.
This results in the production of dilute sweat, so that we can
be cooled by evaporation without losing an undue amount of salt.
Cystic Fibrosis:
•Inherited disorder, caused by a faulty Cl- ion channel. Too
much salt (NaCl) builds up outside the cell membrane
creating a hypertonic solution.
This causes the cells to lose water creating a thick mucous
which collects in airways and in pancreatic and liver ducts.
Liver ducts-clogged, liver becomes cirrhotic.
Lifespan: about 28-30 with meds, liver transplant may be
necessary, gene therapy works in mice not humans (yet)
http://www.pbs.org/wgbh/nova/genome/media/2809_q056_09.html
7.4 LEVELS OF ORGANIZATION
The organization at
each level determines
both the structural
characteristics and the
functions of the higher
levels.
Something that affects a
system will ultimately
affect each of the
system’s components.
Ex. the heart cannot
pump effectively after
massive blood loss.