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Cellular Transport
How do cells move nutrients, products
and wastes in and out of the cell?
Why is this traffic across the membrane
so important?
Cells are filled and surrounded
by watery fluid.
This fluid helps
solids move around
inside, outside the
cell and cross the
cell membrane.
Cell Membrane
The cell membrane
controls what moves
in and out of the cell.
Semi-permeable membrane
Cell membranes only allow
some solutes (solids) to
move across it.
Movement across the
membrane depends on size
and type of the solute
(solid).
Membranes are just so beautiful!!!!!
Types of Transport
High
concentration
Low
concentration
Low
concentration
Down the
concentration gradient
High
concentration
Up the
concentration gradient
Summary: Types of Transport

Passive Transport




Molecules move from area
of high concentration to
area of low concentration
Movement is down the
concentration gradient
No energy needed
Small molecules such as
H2O, O2 and CO2

Active Transport




Molecules move from area
of low concentration to
area of high concentration
Movement is up the
concentration gradient
Energy is required (ATP)
Large molecules, ions
Diffusion –
molecules move from area of
high concentration to area of low concentration.
Concentrations affect Osmosis
Water moves
out of the cell
Water moves
across
membrane
(in/out) at
equal rates.
Water
moves into
the cell
Concentrations affect osmosis
higher amount of
solute outside
cells
equal amount of
solute in and out
of cells
lower amount of
solute outside
cells
Let’s Review
Solution is made of solutes dissolved
in a liquid or gas.
Hypertonic Solution = high amount
of solutes
Hypotonic Solution = low amount of
solutes
Isotonic Solution = equal amount of
solutes
Dynamic Equilibrium is reached
when solutes and water move
across a membrane at equal rates
because concentrations are equal
(isotonic).
Homeostasis = all living systems
need to maintain perfect
concentrations inside each cell
Active Transport
Active transport is the movement of molecules from LOW to HIGH
concentration.
Energy is required as molecules must be pumped against the
concentration gradient.
Proteins that work as pumps are called protein pumps.
Ex: Body cells must pump carbon dioxide out into the surrounding
blood vessels to be carried to the lungs for exhale. Blood vessels are
high in carbon dioxide compared to the cells, so energy is required
to move the carbon dioxide across the cell membrane from LOW to
HIGH concentration.
outside of cell
inside of cell
Carbon Dioxide
molecules
ANALOGY:
ENERGY NEEDED:
Active Transport
NO ENERGY NEEDED:
Diffusion
Osmosis
Facilitated Diffusion
Endocytosis

Moving materials too large to pass
through a membrane INTO the cell



Membrane folds inward, creating a pocket
Membrane closes around the material,
forming a “package”
“Package” breaks away from
cell membrane, bringing the
material into the cell
Exocytosis

Moving materials too large to pass
through a membrane OUT OF the cell



“Package” carries materials to cell membrane
Attaches to membrane and merges together
Materials are pushed out of membrane
• Endocytosis and Exocytosis is the mechanism by which
very large molecules (such as food and wastes) get into
and out of the cell
Cell Size and Shape


As cell grows, surface area is not large enough
to allow resources to travel to all parts of cell
As a result, the cell may:



Stop growing
Divide
Shape


Thin and flat cells (single-celled organisms) have
increased surface area
Long and skinny cells (nerve and muscle) have
increased surface area