Cellular Transport:
Movement of substances
into and out of the cell
The Adventures of Osmosis
X Jones……..
All cells must exist in a liquid environment
Water
Cellular transport is needed:
-because the cell needs specific items
-items needed to produce energy
-through cell respiration
-items needed to produce food
-through photosynthesis
- cell also needs to give off the waste it
produces.
Carbon Dioxide and water
Oxygen and water
Two types of cellular transports:
1. Passive Transport:
Movement of substances into and out
of a cell with NO extra energy required
to be used by the cell.
3 Examples:
-Diffusion
-Osmosis
-Facilitated diffusion
2.Active Transport:
Movement of substances into and out
of a cell but the cell must expend ATP
energy in order to do so.
-These items are either very much needed, very
dangerous or too big to fit through the pores of
the cell membrane
3 Examples:
-Membrane Associated Pumps
-Endocytosis
-Exocytosis
Cell membranes are semi-permeable
-certain items can move in and out of
the cell and others can not.
Items can move
through the
pores/openings
between the
phospholipids
or through the
proteins
embedded in
the bilayer.
Passive Transport
Movement of substances into and out of the
cell and the cell does not use any extra energy.
All molecules have motion:
Solids….molecules vibrate
Liquid….have more energy so
they have a little more
motion
Gas…… molecules have a lot of
energy so they have
much motion
It is the motion of the molecules that moves
them through the membrane with passive
transport.
Three forms of Passive Transport:
1.Diffusion
2. Osmosis
3. Facilitated Diffusion
All three move items into and out of
cell with no extra energy required
by the cell.
Diffusion
-Form of passive transport.
-Movement of any substance from a high
concentration into a lower concentration.
-Diffusion requires no extra energy.
-Items move from a high concentration to a
low concentration due to the motion of the
molecules.
-When molecules move from a high
concentration into a lower concentration we
say the item is moving down the
concentration gradient.
High
Low
If diffusion is the movement of any substance
from a high concentration into a lower
concentration then when will diffusion stop?
When the concentration is equal on both
sides…..no high or low remains.
This is called a Dynamic Equilibrium
Example of diffusion in our body:
Simple Diffusion
The rate of diffusion can be increased by:
1. Increase in temperature
2. Increase in surface area
3. Stirring or shaking
Osmosis:
-Form of passive transport
Therefore requires no extra energy
-Osmosis is the diffusion of water
-Therefore the water must move from a
high to a low concentration
-The diffusion of water is given its own name,
osmosis, because water is such an important
substance for all living organism.
When will osmosis stop?
When there is an equal amount of water on both
sides of the membrane. This is called an osmotic
balance.
The direction of osmosis is controlled
by the concentration of the solution
located inside and outside the cell.
Remember substances like water
move from a high concentration to a
low concentration.
H
L
H
L
Three types of solutions/environments
for a cell:
1. Hypotonic solution:
Hypo =
low
A solution where the concentration
of solute molecules outside the
cell is lower than the concentration
of solute molecules inside the cell.
Hypotonic Environment:
98% water
2% solute
Water enters the cell.
Turgor pressure
increases.
96% water
4% solute
Cell swells in size.
This is called cytolysis.
2. Isotonic solution:
Iso =
equal
A solution where the concentration of
solute molecules outside the cell is
equal to the concentration of solute
molecules inside the cell.
Isotonic Environment:
96% water
4% solute
Water enters and leaves
the cell at an equal rate.
Turgor pressure remains
constant.
96% water
4% solute
Cell remains the same
in size.
This is called
homeostasis or osmotic
balance.
3. Hypertonic solution:
Hyper =
high
A solution where the concentration of
solute molecules outside the cell is
higher than the concentration of
solute molecules inside the cell.
Hypertonic Environment:
94% water
6% solute
Water leaves the cell.
96% water
4% solute
Turgor pressure
decreases.
Cell decreases in
size.
This is called
plasmolysis.
Elodea
Elodea cell in a fresh water environment
1% Saline
1% solute dissolved
In 99% water.
Elodea in a 6% Saline Solution
6% salt dissolved
In 94% water
WHY DID THIS HAPPEN??????????????
Facilitated Diffusion
-final form of passive transport
-requires cell to use NO extra energy
FACILITATE:
-means to help
DIFFUSION:
-form of diffusion so………………
-items move from a high
concentration into a lower
concentration.
Facilitated Diffusion:
-allows for the movement of
important items that are too large to fit
through the pores of the membrane
from a high into a low concentration
with the help of “carrier proteins”.
Carrier proteins: very specific, each
helps only one type of molecule to
pass through the membrane.
Role of Insulin as a carrier protein
Insulin moves glucose
across the membrane
100X faster than it
would move if insulin
is not present.
Active Transport
-movement across the membrane BUT the
cell must expend energy in order for it to
occur.
Examples:
Membrane Associated Pumps MAPs
Endocytosis
Exocytosis
MAPs ~ Membrane Associated Pumps
-energy driven protein motors that move
specific types of solutes across the cell
membrane against the concentration
gradient.
-from a low into a high concentration
High
Low
-in order for the cell to expend energy to
move items across there must be a “real”
need. Items must be really, really needed or
really, really toxic to the cell.
Two types of MAPs:
1. Calcium Pump
2. Sodium-Potassium Pumps
The cell is only willing to pump these three
items across the membrane.
Bones and teeth require a lot of calcium
to remain strong. Therefore they must
“hoard” large amounts of calcium.
Calcium must move from a low
concentration in our blood into a high
concentration in the cells of both the
teeth and the bones.
H
L
H
Muscles require a lot of potassium and create a
lot of sodium as a waste. Therefore they must
“hoard” large amounts of potassium and get rid
of the sodium. Both of these substances must
move from a low concentration into a higher
concentration.
Membrane Associated Pumps
Endocytosis
Endo =
IN
Cyto =
CELL
Hyperlink
Cell membrane surrounds
and engulfs items taking
them into the cell.
Three types of endocystosis:
1. Phagocytosis:
-Cell surrounds and engulfs solid items taking
them into the cell.
Examples:
Amoeba:
White Blood Cells
2. Pinocytosis:
-Cell
surrounds and engulfs substances
dissolved in water, taking them into the
cell.
3. Receptor-mediated Endocytosis:
-items like hormones, vitamins and
minerals attach to specific receptor proteins.
Once attached the membrane pinches together
taking the items in.
Endocytosis
Exocytosis:
Exo =
OUT
Cyto=
CELL
Hyperlink
-Cell membrane opens
up and forces items
out of the cell.
Example:
Contractile Vacuoles
Anal pores
Types of Exocytosis:
1. Excretion:
-waste is forced out of the cell
-mucus, sweat, tears…..
2. Secretion:
-items made by the cell and needed in
other places are forced out of the cell.
-hormones, digestive enzymes,
saliva
Exocytosis
Scenario
If a bone cell is surrounded by 100 units
of calcium and it has 50 units already
stored in it what will occur?
Finally, as
many as
possible of
the 75 units
of Ca+ will
move in due
to MAPs
75
100
/ units of Ca+
75
50
/ units of
Ca+
25 units
move in
by
diffusion