So the other types of transport that allows things
to move across the membrane is active transport.
In an active transport
unlike in passive transport,
now we're able to move things against
the concentration gradient or going uphill
or we're able to move large items from
one side of the membrane to the other.
The difference between active and
passive transport is that in active transport,
an energy expenditure is required.
So we must use energy in order to move
these substances from one place to the other.
So the first type of active
transport is primary active transport.
In this way, the ATP or the energy from ATP is
going to change the shape of a transporter protein
and it's going to pump that substance from one side
to the other against its concentration gradient.
This is found in a lot of different processes
especially in the nervous system and the muscular system.
In secondary active transport, we're
going to use the energy that is released
when something moves down its concentration
gradient to drive the movement of another substance
against its own concentration gradient.
So things are kind of
moving in opposite directions.
And then the last type of
active transport involves vesicles.
Vesicles are membrane-bound
structures that are going to
allow us to move
substances throughout the cell.
And because most of the substances or most of the
membranes in our cell are made of the same thing,
vesicle transport allow things to be
moved and transported and shared
between different parts of the cell a lot easier
cause everything is made up of the same thing.
Think about if you're in the tub and you have
bubbles, when two bubbles bump into each other,
they don't pop, they just kind of
fuse and make a bigger bubble.
And so, there multiple different
types of vesicular transport.
One is endocytosis where we're going to bring
substances into the cell in through a vesicle.
A ligand will bind to a receptor on the
membrane and that will trigger the enfolding
of that portion of the membrane
until it forms a small vesicle
and then blebs off toward
the inside of the cell.
Another process that's used is phagocytosis.
Phagocytosis is also
referred to as 'cell eating'
because the cell is going
to take in large particles
by engulfing them from the external
environment and bringing them into the cell.
Usually from here, it will use other processes in order
to break that large particle down into usable units.
As well, we also have a process
known as 'cell drinking' or pinocytosis.
In pinocytosis, we're going to bring
in a bunch of smaller substances
through the cell by bringing them into small
vesicles sometimes referred to as caveoli.