Download Cellular Homeostasis & Transport

Cellular Homeostasis
Homeostasis is the used to describe the
overall health and condition of the cell.
You want to maintain certain levels for the cell
to function normally.
you need to maintain a certain level of oxygen,
food, water, etc… to function properly…well a
cell needs to maintain things too.
A cell membrane helps organisms maintain
homeostasis by controlling what comes in and
out of a cell.
Small molecules can come through the plasma
(cell) membrane. This is called the
Permeability of the membrane.
This movement of substances across a cell
membrane without any energy used is called
PASSIVE TRANSPORT
TYPES OF
PASSIVE
TRANSPORT
1. DIFFUSION – the movement of molecules
from an area of high concentration to an area
of low concentration
High
Low
The distance it needs to travel we will call the
Gradient.
So we are talking about concentrations, and
the distance they diffuse across (the
membrane)… so this is known as
CONCENTRATION GRADIENT
So molecules that move through the lipid layer
from high to low concentration is an example
of DIFFUSION
Low
High
What happens when you have the same
numbers of molecules on both sides of the
cell membrane?
When you have the same number of molecules
on both sides of the cell membrane you have
something that is called EQUILIBRIUM
There’s no concentration gradient…both sides
are equal.
50%
50%
30%
70%
60%
40%
51%
49%
46%
54%
Diffusion will only occur with small molecules,
molecules that are large will not be able to go
through the cell membrane easily.
Only select small molecules go through the
membrane…So the cell membrane is then called
a
“SEMI-PERMIABLE MEMBRANE”
2. Facilitated Diffusion
Special Proteins in the cell membrane are designed to
diffuse one exact type of substance through the
protein without any energy being used by the cell
Blurry
MOVIE!!!
Non-Blurry
Movie
3. OSMOSIS
Osmosis is almost the same as
diffusion…except we are talking about water
and nothing else.
Osmosis – is the movement of water molecules
from a high concentration to an area of low
concentration
However there are 3 types of Osmosis…
ISOTONIC
– is a state of equilibrium. Where water
molecule levels are equal on both sides of
the cell membrane.
- water can freely flow in or out of the cell
50%
50%
Animal Cell
50%
Plant Cell
50%
. HYP
OTONIC
-this is where there is High concentration of
pure water OUTSIDE the cell and a Low
concentration of water INSIDE the cell.
- so if water rushes in, the cell starts to swell.
70%
30%
In Animal cells, if too much
water comes in, the cell
expands and bursts open.
This is called LYSED or
Haemolysis in blood cells.
o
Hyp tonic In Plants…
- water rushes into the cell, but
the cell does not explode ! Why?
70%
30%
-plant cells have a tough double
cell wall, so they hold the cell
shape even when water rushes in
so it doesn’t explode!
The pressure of the water
pushing against the cell walls is
called TURGOR PRESSURE
HYPERTONIC
-is where you have a higher concentration of
water INSIDE the cell, than outside the cell
-So water moves out of the cell !
30%
70%
In animal cells all the water
leaves the cell, so it shrivels
up and can possibly die
In blood cells this is known
as Crenation
Hypertonic In Plants
-water is leaving the cell
30%
70%
but the plant cell wall
stays in place. All the
insides start to shrivel up.
This action is called
PLASMOLYSIS
Diffusion movie
Movie on RBC
Active Transport
Endocytosis &
Exocytosis
We know that the concentration gradient
means moving from a area of high
concentration to an area of low concentration
Low
High
Occasionally this needs to be moving from low
to high gradient”
High
Low
To go against the normal concentration
gradient it will require energy to be spent.
Moving from Low to High on the concentration
gradient, using energy is a process known as
ACTIVE TRANSPORT
It requires special membrane
proteins (carrier proteins) that
are often called “pumps” because
they pump against the normal
concentration gradient
The energy that is added causes
the protein to change shape,
allowing the molecule to be
carried in.
Molecule to
be carried
Energy
Molecule
being carried
Active transport in the cells is
normally used for large molecules
Molecule to
be carried
However, concentrations of
sodium, Calcium, and Potassium
are also pumped through for
different cell functions.
Energy
Molecule
being carried
The most common active transport pump we
talk about in Biology is the Sodium-Potassium
pump.
1. The protein in the membrane
attracts sodium ions into special
receptors.
2. ATP give up 1 of its “Phosphorous
ions” to start the pump. This is
known as Phosphorylation.
3. The protein now begins to change
shape & move the Na+ against the
concentration gradient. Releasing it
on the other side of the membrane.
4. The protein now attracts
Potassium ions (K+) into specially
designed receptacles.
5. The binding of the Potassium
causes “De-phosphoryliation” as
the phosphate group falls off.
6. The “De-phosphoryliation”
causes the protein to change
shape and move the K+ ions
across the concentration
gradient. Ready to revieve new
NA+ ions.
Active transport (sodium / potassium pump) is
very important because it helps return the
muscle cells to normal homeostasis levels after
muscle contraction.
Otherwise, you would not be able to constantly
make muscles contract.
MOVIE 1
MOVIE 2
So how do cells eat?
They actually have a way of bringing in
material into the cell to digest. It is called
ENDOCYTOSIS
(Endo = towards)
There are 2 types of Endocytosis:
PINOCYTOSIS – “cell drinking” where the cell
engulfs solutes or fluids
PHAGOCYTOSIS – “cell eating” where whole
particles or large compounds are brought in
STEPS OF ENDOCYTOSIS
1. The cell membrane forms a pouch on the cell surface
and brings in the material
2. The cell membrane’s pouch then surrounds the material
3. Eventually the pouch closes completely capturing the
material inside
4. The pouch pinches off from the cell membrane to
become a vesicle
1
2
3
4
Cells also have a way to get rid of waste or
proteins in a process called EXOCYTOSIS
(exo = exit)
It’s practically the reverse of endocytosis.
The Golgi body forms a vesicle that is
packaged for leaving the cell
1. The vesicle approaches the cell membrane
2. The vesicle fuses with the cell membrane
3. The pouch now opens up and expels it’s
material
4. The material is released outside of the cell
MOVIE!!
1
2
3
4
VOCABULARY!
Passive Transport
Plasmolysis
Diffusion
Facilitated diffusion
Concentration gradient
Active Transport
Equilibrium
Carrier proteins
Semi-permeable membrane
Osmosis
Endocytosis
Isotonic
Pinocytosis
Hypotonic
Phagocytosis
Lysed
Exocytosis
Turgor Pressure
Hypertonic