Cell Transport
There are TWO types of cell transport:
1) Passive transport- NO ENERGY required.
2) Active transport- ENERGY required.
Passive Transport
In passive transport, substances
move across the cell membrane
WITH the concentration gradient.
Substances move from HIGH to
LOW concentrations.
High concentration
of substances
Low
Concentration
This is ALSO known as DIFFUSION.
Simple _________= The movement of molecules from high concentrations to low
concentrations.
________= the diffusion of WATER.
Concentration gradient= _________________________________________________
(must exist in order for molecules to flow).
Brownian movement
Molecules are able to naturally diffuse due
to a mechanism called _________
movement- the random
_____________________.
Particles suspended in a gas or a liquid are
bombarded by fast moving atoms or
molecules.
There are THREE types of passive transport:
1)
2)
3)
Osmosis
_____________________
____________
Osmosis
Osmosis is diffusion of _____.
Which of the diagrams
at right best represents the
movement of molecules in
osmosis?
A, B, C or D?
Cell Environments
Too much water in the cell= __________
Cell will _____ if environment remains hypotonic;
percentage of water is higher outside the cell than in.
Too little water in cell= __________
Cell will ______ if it is exposed to a hypertonic
environment; percentage of water is lower outside the
cell than in.
Cell environment where concentrations of water are
equal inside and outside the cell= _________(ideal)
Hypertonic
A cell is in a hypertonic solution if the
concentration of
_______________________________ than
the concentration outside the cell.
Water diffuses from high to low.
Water _______________.
This is why you should NEVER drink salt
water. Doing so will severely _________ you!
Think “SALT SUCKS”
Hypotonic
A cell is in a hypotonic solution if the
concentration of
_________________________________
than the concentration outside the cell.
Water diffuses from ___________.
Water _____________________.
Isotonic
Water concentration stays _____ inside and
outside the cell.
Water enters and leaves the cell at equal
rates.
________________________.
Facilitated Diffusion
The passive transport of materials across
the cell membrane with the aid of
_________; a common method of moving
______ and ___________.
Ion channels
Special transport proteins with _________ that can open and close.
Allow ______in and out of the cell (examples of ions= _____,_____,_____).
Let’s review
__________ transport does NOT require energy.
Active transport DOES require ___________.
During passive transport, substances move from
_______ to ______ concentrations.
____________ is the diffusion of water.
_________________ solutions could cause a cell to
burst.
Facilitated diffusion uses proteins to allow
___________ and amino acids into or out of the cell.
Ion channels are proteins with special __________ that
can open or close to let _______ in or out.
Active Transport
Active transport moves substances across the cell membrane AGAINST the
concentration gradient (energy needed to do so).
Substances move from LOW to HIGH concentrations.
(Opposite of passive transport).
Examples of Active Transport
1) Exocytosis
2) Sodium-Potassium Pump
Endocytosis
Recall that active transport requires energy
(ATP).
Molecules that are actively transported go
AGAINST the concentration gradient (or
“uphill”).
Endocytosis
A process in which cells surround and engulf substances that are TOO BIG to
enter the cell. The cell uses its own membrane to engulf the substance into
a vesicle and bring it in.
Exocytosis
Opposite endocytosis. When a cell forms a vesicle around unwanted particles
and expels it OUT of the cell.
Endocytosis vs. Exocytosis
*Endo means “in”;
Exo means “out”.
*Cyto means cell
(Endocytosis= in cell;
Exocytosis= out of cell)
The Cell Membrane
Functions)
1)The cell membrane regulates what enters and leaves the cell.
2)The cell membrane provides protection and support for the cell.
3) Communicate with other cells.
The cell membrane acts as a BARRIER, separating the cell’s inside from its
outside.
The cell membrane is also known as the plasma membrane, and is often
referred to as the semi-permeable membrane.
Semi-permeable refers to the tendency for the cell to allow some materials in,
but not all (like a screen or a net).