Hi. It's Mr. Andersen and in
this video I'm going to talk about adenosine triphosphate. Otherwise known as ATP. ATP
is usually shown with this yellow starburst behind it. And that's because it contains
energy. In fact it's the energy coinage of all life on our planet. And most of you probably
know that but you might not know the structure of ATP. And so let's begin with the adenine.
Adenine is a purine and it's a nitrogenous base. That means that the black in going to
be carbon but the blue is going to be nitrogen. Where have we seen nitrogenous bases? Remember
that's going to be the rungs found on the inside of DNA. We also have a ribose sugar.
And then we're going to have not one phosphate group. Phosphate is phosphorus surrounded
by oxygen. But we're going to have three phosphate groups. And so let's start with the adenine
and the ribose. They're attached together and they form a chemical called adenosine.
If we add a phosphate to that, we have AMP or adenosine monophosphate. If we were to
add another phosphate to that we've now got adenosine diphosphate or ADP. But if we add
that third phosphate we now have ATP, or adenosine triphosphate. Now these last phosphates are
important. In fact I like to think of the bond between these last two phosphates like
a spring. As we attach that last phosphate on, we're storing energy. And so there's potential
energy in that bond. There's also going to be potential energy in this bond right here
as well. And so when we release that phosphate, we can release a little bit of energy. And
so let's look at that. And so what is ATP? Here it is again? So we've got our adenine,
our ribose sugar. And then we have our three phosphates. But you can think of it like a
recharged battery. It's a battery that's charged up. It has a certain amount of potential energy.
In fact if we were to take ATP, which would just look like salt if you were to have it
in a solid form, and we were to add it to water, it would all hydrolyze. In other words
it would all breakdown into ADP. And so let's look at what's going on here. So if this is
water, that water will break this last phosphate group. In other words we're going to add an
OH on one side and H on the other side. Remember we call that hydrolysis or breaking with water.
And we create ADP. Now we have just two phosphates here. Well what happens to that third phosphate?
It's released. And so lots of times when you're dealing with ATP you're going to see this
P with a subscript of i. What does that stand for? That's this phosphate group that's been
given off. And since there is a certain amount of potential energy in this bond, when it's
released that phosphate has a certain amount of potential energy as well. So in other words,
if we were to let ATP just sit in water, it would all eventually hydrolyze and it would
all become ADP and we'd have these loose phosphates. That's going to be like a battery that's lost
its charge. And so what do we do in life? Well in life we're going to tap some energy.
And so we could do that in respiration by breaking down glucose. Or in photosynthesis
by taking in energy from the sun. And we're going to attach that phosphate group again.
And that's called a dehydration reaction. And so when we attach the phosphate we now
make ATP. When we break it then we're going to release energy. And so let's start by talking
about the building. And so when do we produce ATP? We're going to do that in cellular respiration.
And so remember on the inside of that mitochondria we have these proteins called ATP synthase.
And what happens in all of respiration is we build up a gradient of protons on the outside
of that. And as they flow in, we make ATP. Now it's worth pausing for just a moment and
talking about, you know, how does ATP know where to go. And how does ADP know where to
go? Well if you're to think about it, let's look right here. As we're converting ADP and
a phosphate back into ATP, they're disappearing. So you can think of in the mitochondria that's
going to be the lowest amount of ADP and phosphate is going to be found right here. Why is that?
It's because they're going to be converted into ATP. Well where's the ATP going to flow
from there? Well diffusion is going to move it from an area of high concentration to low.
And so it's going to move wherever it's used. Once it's used, it converts back to ADP and
a phosphate. And that's going to come right back here to the inside of the mitochondria.
Now remember plants are also going to produce ATP. They're going to do it on the thylakoid
membrane which is going to be this membrane right here on the inside of the chloroplast.
What are they using to make ATP? They're using light, energy of light to do that. How is
this different than the mitochondria? Remember the phosphates or excuse me, the hydrogen
protons are going to be on the inside of the thylakoid membrane. As they flow out that's
going to make ATP. What do we use that for in plants? Remember out here in the Calvin
Cycle we're going to use that to make sugars. Now plants also have mitochondria so they
can break down that sugar and make ATP. And so that's how we're producing it. What does
it do though? Once we release that phosphate, what is it used for? Well let me give you
three good ways that it's used. So if we release that phosphate it can be used in active transport.
And so this right here is the sodium potassium pump. This is going to be found on most of
the cells in your body. But it's especially important in the neurons of your body because
you maintain this gradient and that's how nerves actually work or impulses work. And
so let's watch what's going on. We have ATP right here. It's going to give up that phosphate.
And that phosphate is going to bind to this sodium potassium pump. As it does that, it's
going to use the energy of that phosphate to pump three sodium ions out. We're then
going to have two potassium ions that will bind to the inside of that pump and that's
going to flow to the inside as we release that phosphate. So again, what are we using?
We're using active transport to pump sodium out and potassium in. How much of your energy
right now is going to that? About 20% of the energy in your body right now is going to
ATP which is running the sodium potassium pump and keeping all of those neurons working.
So it's really important. How else do we use ATP? Well when we release that phosphate our
muscles move using ATP. And so what's going to happen is the phosphate will bind to this
myosin The myosin is going to be a protein and it will attract that to an actin and it's
going to cause your muscle to contract. And so your muscles contract using this phosphate
that is released from ADP. What do we have to do with that phosphate in ADP? Again, we
have to regenerate ATP so that we can do this again. Where else do we have this? Well in
the formation of polymers. And so when we're building polymers the easiest way to do that
is to add a phosphate. And so let me kind of show you where we're at. This is tRNA.
Remember tRNA is going to transfer the amino acid to the ribosome. And it's going to build
proteins. And so how does that work? First thing is we're going to have ATP and that's
going to bind to the enzyme. And then it's going to allow us to attach that amino acid
on to the tRNA. And so we can build big polymers like that. In fact, RNA is built using ATP.
What does that mean? Well let's go to it. ATP is old school. What does that mean? It's
been around from the beginning of time. It was used by LUCA. LUCA remember is the Last
Universal Common Ancestor. In other words that is the ancestor of all cells on our planet.
And so this is a phylogenetic tree of all life on our planet. We would have us, eukaryotes
over here. We have archaea. And then all of this is bacteria. But scientists believe that
that first ancestor of all life had a few properties. Number one they used ATP. They
had RNA and DNA. They had the ability to use glucose. They used proteins, ribosomes, membranes
and ion channels. And so let's say that LUCA kind of looked like this. It's a simplified
cell. Well how did scientists come up with this? Why is it that this cell had to have
all of those things? Well that's because those things are found in all cells on our planet.
Not only us, but it's going to be found in prokaryotic cells and archaea. So we know
that that first organism had that and used ATP for its energy. And that's because it's
found in all cells. And so ATP has been there from the beginning. But let's look at how
prevalent ATP is in these other molecules. And so let's look at RNA. So what's RNA. Remember
it's going to be kind of the worker of DNA. But let's look right here into one of these
nucleotides inside RNA. What do we find? Well we find adenine. We find a ribose sugar. And
then we have a phosphate. Well what does that look like? That looks like ATP. Except only
one phosphate instead of two. And so when I said we're building RNA, we really are building
that using ATP. And you can see how cool that is. That the ATP, the energy that we use or
the molecule that we use for energy was also a part of that first genetic code. And so
it was kind os co-opted for two uses. Let's look at DNA. DNA also has this adenine. It
has a deoxy sugar. And there's an enzyme that's actually going to switch that. But it's also
really close in structure to ATP. All cells use glucose. What do we use glucose to do?
Remember we're going to breakdown glucose in the mitochondria. And we're going to make
ATP. All life is built of proteins and ribosomes do that. Well, how do we do that? Remember
it's going to be ATP that's binding those amino acids on to the tRNA so that we can
build them inside the ribosome. And remember all cells are also going to have membranes
and use ion channels. Well if you look at it, that ion channel like that sodium potassium
pump uses ATP. And if you were to look even in the phospholipids that make up the membrane,
what do we find right here in the middle? We find that phosphate group. And so ATP has
been around forever. It's used by all of life. It's pretty simple. Just add a little bit
of energy to ADP and you've got ATP. If you release that energy, give off a phosphate
you can do work. So that's ATP. And I hope that was helpful.
