Transport in the Cell
In a way a cell is like a miniature version of
you. It requires nutrients and, in the
process of breaking down the nutrients, the
cell produces wastes. So there has to be a
way to get nutrients in and wastes out.
One particular part of the cell plays a
huge role in controlling what enters
and leaves the cell, so this organelle
is in charge of CELLULAR
TRANSPORT.
Cell Membrane
 Phospholipids
– main
component of the cell
membrane
 Cholesterol – prevents close
packing of the lipids
 Proteins – transport ions
through the membrane
General Terms
Concentration Gradient –
The unequal distribution of particles
Concentrations
Cell Transport
2 Main Types of Transport:
Passive Transport
Active Transport
No Energy Needed
Molecules naturally want to
reach a balance on either side
of a membrane moving from
high to low concentration
“Homeostasis”
The cell’s version of
energy is needed - ATP
It moves molecules from low
concentration to high
concentration.
Cell Transport
PASSIVE TRANSPORT
The movement of
molecules from a
HIGH to LOW
concentration
http://www.stolaf.edu/people/giannini/fl
ashanimat/transport/diffusion.swf
Cell Transport
PASSIVE TRANSPORT
the
diffusion
of water
http://www.stolaf.edu/people/gianni
ni/flashanimat/transport/osmosis.sw
Cell Transport
PASSIVE TRANSPORT
More General Terms
Pressure – the
water pressure in cells
 Osmotic
Turgor pressure – the
water pressure in plant
cells
 Plasmolysis – Process
where the cell membrane
pulls away from the cell
wall due to water loss

Solutions
Passive Transport
Solutes:
Dissolved
substances
like salt
and sugar.
75% solutes
0 % solutes
1. Where is the
concentration of solutes
the greatest?
2. Where is the
concentration of water
the greatest?
3. Which molecule would
be easier to move – the
solute or the water?
Passive Transport
75% solutes
0 % solutes
As a result,
the smaller
molecule,
water, will
move into the
cell causing
the cell to
expand.
Passive Transport
75% solutes
0 % solutes
Since the
concentration
of the solutes
OUTSIDE of
the cell is
lower, then the
solution is
considered to
be
HYPOTONIC.
Solutes
Outside the cell
Passive Transport
50% solutes
50 % solutes
As a result, the
smaller
molecule, water,
will move into
and out of the
cell at an equal
rate causing the
cell to remain
the same size.
Passive Transport
50% solutes
50 % solutes
Since the
concentration
of the solutes
OUTSIDE of
the cell is
EQUAL or the
SAME, then
the solution is
considered to
be ISOTONIC.
Solutes
Outside the cell
Passive Transport
20%
20%
solutes
70 % solutes
As a result,
the smaller
molecule,
water, will
move out of
the cell
causing the
cell to shrivel.
Passive Transport
20% solutes
70 % solutes
Since the
concentration of
the solutes
OUTSIDE of the
cell is HIGHER or
ABOVE, then the
solution is
considered to be
HYPERTONIC.
Solutes
Outside the cell
Everyday examples
of solutions
 Hypertonic:
Alcohol,
Caffeine, Ocean water, Epson
Salt bath
 Hypotonic: Distilled water
 Isotonic: Blood
Cell Transport
Active transport
It moves molecules from low concentration
to high concentration.
Cell Transport
Why does active transport
need energy?
Because the molecules are moving against the
CONCENTRATION GRADIENT.
Cell Transport
Sometimes a substance that a cell needs
to transport in is too large to fit
through the cell membrane, so the
membrane moves around the substance.
Endocytosis - the cell
membrane engulfs a
substance by
surrounding it and
forming a “vessicle.”
Cell Transport
Exocytosis – The cell needs to rid the
cell of a waste or substance so it forms
a “vessicle” around it and releases the
substance at the cell membrane.
50% solutes
50 % solutes
0% solutes
50 % solutes
100% solutes
50 % solutes
90% solutes
80 % solutes
10% solutes
100 % solutes