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ATP: 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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  • blobby green style avatar for user Muhammad Asad Abbas
    please tell me about reducing sugars and whether sucrose is reducing or non reducing?
    (0 votes)
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    • aqualine ultimate style avatar for user 54222
      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)
  • purple pi purple style avatar for user JD
    Adenosine triphosphate and adenosine diphosphate are frequently mentioned. Is there an adenosine quadphosphate, or any adenosine with more than three phosphoral groups?
    (2 votes)
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  • aqualine ultimate style avatar for user 54222
    Just curious, can some animals photosynthesise or do plants only do that?
    (2 votes)
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  • orange juice squid orange style avatar for user RosemarieTsai
    so, just to be sure, there are only two high energy bonds in an ATP? (from )
    (2 votes)
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    • female robot grace style avatar for user tyersome
      Correct, 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
      (3 votes)
  • blobby green style avatar for user Emma Jeong
    Is combining with water the only way for ATP to turn into ADP and release energy for the cell to function?
    (2 votes)
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  • primosaur ultimate style avatar for user HannibalTheCannonball
    Dumb question: Adenosine triphosphate (ATP) has the prefix tri in it. Adenosine diphosphate (ADP) has di as the prefix. Why is DIphosphate used instead of BIphosphate (if bi means 2)?
    (1 vote)
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  • aqualine ultimate style avatar for user william
    this video shows us that the reaction that change ATP into ADP relase some energy
    the thing i'd like to ask is what is the form of this energy is it always in the form of heat?
    (2 votes)
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    • mr pink red style avatar for user The Nano Drop
      It is chemical energy. However, energy transfer is not 100% efficient and some energy is lost as heat. (If I remember correctly, only about 35% of the energy from the breaking of the phosphate bonds of ATP is utilized by the cell - therefore, 65% of energy is released as heat.)
      (2 votes)
  • starky sapling style avatar for user Saryan Khanal
    So ATP converts into ADP and releases energy which we use. But where does the third phosphate group come from after you utilise the energy. In other words, how does ADP convert back to ATP. I can understand that as phosphate is phosphorus + oxygen (PO4), we receive oxygen as we breathe. But where do we receive the phosphorus from when we exercise and why do we need it?
    (2 votes)
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  • male robot johnny style avatar for user amit
    Can you tell me that if we use the energy to combine or i must say that if we react ATP and h20 together ito form ADP and energy. So can this process can be reversal too?
    (1 vote)
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  • piceratops tree style avatar for user Samin Yead
    Well, we generally know that bond breaking requires energy while bond forming releases energy. So, I still find this a bit confusing as to why would energy be released when ATP is broken to form ADP? Are there reactions other than this where bond is broken to release energy?
    (2 votes)
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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.