In this video we're going to talk about active cellular transport both primary and secondary.
So in previous videos we talked about passive transport and passive transport did not require
any energy. It was simply taking a substance that was in a high concentration and moving it
along its gradient down to a low concentration. This didn't require any energy to go from a high
concentration to a low concentration. Now with active transport, active transport is actively
moving something against its concentration gradient. So the primary example for active
transport is the sodium potassium pump. The sodium potassium pump is going to move three sodiums in
this protein. And this protein pump is going to attach three sodiums from inside the cell. ATP
is going to attach onto the protein and using the power going from ATP to ADP when it breaks
off that phosphate group, that energy is going to power this pump. So we're going to change shape.
The sodium is now going to leave the cell and two potassium are going to attach into the cell. That
phosphate group is going to break away, and our little potassiums are going to be brought
into the cell. And the cycle will start all over again. So this sodium potassium pump is going to
pump out again three sodiums outside the cell and it's going to bring in two potassiums with
this pump. It's directly dependent on ATP to pump these ions against their concentration
gradients putting more sodium outside the cell and bringing more potassium inside the cell. So
this gives the cell an electrical charge and overall electrochemical gradient where it
is more positive outside the cell, and inside the cell overall the charge is more negative. Because
of the ions going against their gradient. Because of this sodium potassium pump the
primary example for primary active transport. It requires energy because it's pushing everything
against its concentration gradient. Secondary active transport or Co-transport is based
upon this electrochemical gradient that was set up with primary active transport. We set
up this electrochemical gradient where we had all these sodiums pushed against their concentration
gradient out here in the extracellular fluid. And now remember with simple diffusion we want those
things to go and follow down their gradient. So with secondary active transport our sodium
is going to follow its concentration gradient. And it's going to go from high to low. So it's
going to attach onto these proteins right here and when it does it's gonna bring in a buddy. So we're
gonna bring in glucose as well hence the name co-transport. So it's bringing in two things.
So the cell is going to bring in sodium which is going to follow its concentration gradient from high to low into the cell. And then it's going to bring in glucose as well. Which
now is having a higher concentration gradient inside the cell. So this is secondary active
transport based again upon the primary active transport of sodium potassium pump that's set
up an electrochemical gradient between the outside of the cell and the inside of the
cell. So there's different proteins involved in transportation. You could have a uniporter
that's just gonna carry one molecule. It carries the one guy and it moves it in or out.
we could have also molecules protein molecules that will carry two things. If they're carrying
two things they could be a symporter or an antiporter. So a symporter would carry two different
molecules in the same direction. They're a symporter since we were just talking about the sodium and
glucose. Sodium and glucose comes inside the cell with a symporter. With an antiporter we
may bring in one thing inside the cell, and one thing outside the cell. So sodium potassium pump
where we were pumping sodium outside and we wanted to bring potassium inside the cell. So
those are different types of transport proteins. Uniporters move one thing, symporters and
antiporters are co-transporters that move two different things. If they move in the same
direction they're a symporter. If they move in opposite directions they're antiporters.