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Course: Biology library > Unit 7
Lesson 4: ATP and reaction couplingATP: Adenosine triphosphate
Learn more about ATP: how it stores energy, and how that energy is released when it's converted to ADP and phosphate. Created by Sal Khan.
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- Adenosine triphosphate and adenosine diphosphate are frequently mentioned. Is there an adenosine quadphosphate, or any adenosine with more than three phosphoral groups?(48 votes)
- AQP would be far to unstable, or too highly electronegative to ever be formed in natural circumstances. Their are no biological processes as we know that can add a fourth phosphate group group to ATP.(17 votes)
- please tell me about reducing sugars and whether sucrose is reducing or non reducing?(10 votes)
- Non-reducing sugars do not have an OH group attached to the anomeric carbon so they cannot reduce other compounds. All monosaccharides such as glucose are reducing sugars. A disaccharide can be a reducing sugar or a non-reducing sugar. Maltose and lactose are reducing sugars, while sucrose is a non-reducing sugar.(5 votes)
- Nice explanation, but why the adenosine part? Couldn't just the phosphates store energy on their own?(14 votes)
- Atin the video, it is stated that "the first part this molecule [adenosine portion]" must be broken to release enough energy for the cell. So, to answer your question, the phosphates can store energy, but the adenosine part is also critical to energy production/cellular respiration as a crucial step along the way. For example, the breaking down of the ENTIRE ATP molecule is important for the ADP/ATP cycle that is required for cellular respiration. I'm kind of late on this, but hopefully this helps :) 0:47(8 votes)
- Since ATP is unstable in water, how does it move to the cell membrane to act on the active transport?(10 votes)
- Since ATP is unstable and present in very low amounts in our bodies, we have to produce it from ADP and P.
Every molecule of ATP is actually recycled 1300 times a day!
The mitochondrion has ATP synthase which helps phosphorylation of ATP and its transport out of the mitochondrion into the cell. It is the ADP/ATP carrier which helps import and export of ATP out of mitochondria.
That's the way it moves through membranes.
Any cell of our body has mitochondria. ATP is basically locally produced.
That's how we have enough ATP which generates nerve impulses, muscle contraction. DNA replication etc.(14 votes)
- Someone explain Hydrolysis?(6 votes)
- hydrolysis is when a chemical bond occurs in the presence of water, but during the bond a water molecule is taken in and divided between the two monosaccharides. The opposite of this is a condensation reaction, where a water molecule is the outcome of the reaction.(17 votes)
- Question: Where does the ATP come from?(11 votes)
- At, you mention that energy is released when the chemical bond is broken because this bond is where energy is stored. Since energy is stored in bonds, why not just have one phosphate (Adenosine monophosphate) which is added and released for energy purposes? Do the other two phosphates add more energy to the bonds when released or is there some other purpose? 5:10(7 votes)
- The bond between phosphoryl groups (known as a phosphoanhydride bond) is very high energy.
In contrast, the bond between a phosphoryl group and Adenosine is much lower in energy.
These reactions:ATP + H₂0 → ADP + Pᵢ
ADP + H₂0 → AMP + Pᵢ
yield more than twice the energy compared to this reaction:AMP + H₂0 → Adenosine + Pᵢ
So, yes the additional phosphates result in higher energy bonds.(5 votes)
- is ATP polar?(5 votes)
- At, why does Sal say that they're called phosphoryl groups? (my teacher calls them phosphate groups) 1:29(4 votes)
- A phosphoryl group has 3 oxygens connected to the phosphorus atom, whereas a phosphate group has 4 oxygens connected to the phosphorus atom. So Sal's terminology was consistent with his drawing of a phosphoryl group breaking off. The phosphoryl group will become a phosphate group after bonding with the O from H2O.(6 votes)
- At, Sal says that "these are high energy bonds". I understand what that means, but can someone please explain why these particular bonds are in a higher energy state than other bonds? 2:22(5 votes)
- You see those negatively charged oxygen? Those negatively charged guys are all (three phosphates) "stacked" together that want to repel each other. That's what makes it have high energy.(2 votes)
Video transcript
Sal: ATP or adenosine triposphate
is often referred to as the currency of energy, or
the energy store, adenosine, the energy store in biological systems. What I want to do in this video is get a better appreciation of why that is. Adenosine triposphate. At first this seems like
a fairly complicated term, adenosine triphosphate, and
even when we look at its molecular structure it seems
quite involved, but if we break it down into its constituent
parts it becomes a little bit more understandable and we'll
begin to appreciate why, how it is a store of energy
in biological systems. The first part is to break
down this molecule between the part that is adenosine
and the part that is the triphosphates, or
the three phosphoryl groups. The adenosine is this
part of the molecule, let me do it in that same color. This part right over here is adenosine, and it's an adenine connected to a ribose right over there, that's
the adenosine part. And then you have three phosphoryl groups, and when they break off they
can turn into a phosphate. The triphosphate part
you have, triphosphate, you have one phosphoryl
group, two phosphoryl groups, two phosphoryl groups and
three phosphoryl groups. One way that you can conceptualize
this molecule which will make it a little bit easier
to understand how it's a store of energy in biological systems
is to represent this whole adenosine group, let's just
represent that as an A. Actually let's make that an Ad. Then let's just show it bonded to the three phosphoryl groups. I'll make those with a P
and a circle around it. You can do it like that,
or sometimes you'll see it actually depicted, instead
of just drawing these straight horizontal lines
you'll see it depicted with essentially higher energy bonds. You'll see something like that to show that these bonds have a lot of energy. But I'll just do it this way
for the sake of this video. These are high energy bonds. What does that mean, what does that mean that these are high energy bonds? It means that the electrons
in this bond are in a high energy state, and if
somehow this bond could be broken these electrons are
going to go into a more comfortable state, into
a lower energy state. As they go from a higher
energy state into a lower, more comfortable energy state they
are going to release energy. One way to think about it
is if I'm in a plane and I'm about to jump out I'm
at a high energy state, I have a high potential energy. I just have to do a
little thing and I'm going to fall through, I'm going to fall down, and as I fall down I can release energy. There will be friction
with the air, or eventually when I hit the ground
that will release energy. I can compress a spring
or I can move a turbine, or who knows what I can do. But then when I'm sitting on my couch I'm in a low energy, I'm comfortable. It's not obvious how I could
go to a lower energy state. I guess I could fall asleep
or something like that. These metaphors break down at some point. That's one way to think
about what's going on here. The electrons in this bond,
if you can give them just the right circumstances they
can come out of that bond and go into a lower energy
state and release energy. One way to think about it, you start with ATP, adenosine triphosphate. And one possibility, you put
it in the presence of water and then hydrolysis will take
place, and what you're going to end up with is one of these things
are going to be essentially, one of these phosphoryl
groups are going to be popped off and turn into
a phosphate molecule. You're going to have
adenosine, since you don't have three phosphoryl
groups anymore, you're only going to have two phosphoryl
groups, you're going to have adenosine diphosphate,
often known as ADP. Let me write this down. This is ATP, this is ATP right over here. And this right over
here is ADP, di for two, two phosphoryl groups,
adenosine diphosphate. Then this one got plucked
off, this one gets plucked off or it pops off and it's
now bonded to the oxygen and one of the hydrogens
from the water molecule. Then you can have another hydrogen proton. The really important part of
this I have not drawn yet, the really important part of it, as the electrons in this
bond right over here go into a lower energy state they
are going to release energy. So plus, plus energy. Here, this side of the reaction, energy released, energy released. And this side of the interaction you see energy, energy stored. As you study biochemistry
you will see time and time again energy being used in
order to go from ADP and a phosphate to ATP, so
that stores the energy. You'll see that in things
like photosynthesis where you use light energy to essentially, eventually get to a point
where this P is put back on, using energy putting this P
back on to the ADP to get ATP. Then you'll see when biological
systems need to use energy that they'll use the ATP
and essentially hydrolysis will take place and they'll
release that energy. Sometimes that energy could
be used just to generate heat, and sometimes it can be
used to actually forward some other reaction or
change the confirmation of a protein somehow,
whatever might be the case.