If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

ATP: Adenosine triphosphate

ATP, or Adenosine Triphosphate, is the energy currency in biological systems. It's made up of adenosine and three phosphate groups. Energy is stored when ATP is formed and released when it's broken down into ADP (Adenosine Diphosphate) and a phosphate group. This energy release powers various biological processes. Created by Sal Khan.

Want to join the conversation?

  • 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?
    (52 votes)
    Default Khan Academy avatar avatar for user
  • blobby green style avatar for user Muhammad Asad Abbas
    please tell me about reducing sugars and whether sucrose is reducing or non reducing?
    (10 votes)
    Default Khan Academy avatar avatar for user
    • 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)
  • piceratops ultimate style avatar for user David Procházka
    Nice explanation, but why the adenosine part? Couldn't just the phosphates store energy on their own?
    (15 votes)
    Default Khan Academy avatar avatar for user
    • hopper jumping style avatar for user Lucy Z.
      At in 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 :)
      (9 votes)
  • marcimus orange style avatar for user Chia-Ying  Chaing
    Since ATP is unstable in water, how does it move to the cell membrane to act on the active transport?
    (11 votes)
    Default Khan Academy avatar avatar for user
    • winston baby style avatar for user Ivana - Science trainee
      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.
      (15 votes)
  • male robot johnny style avatar for user Ninad Tengse
    Someone explain Hydrolysis?
    (7 votes)
    Default Khan Academy avatar avatar for user
    • mr pink red style avatar for user Henry LaGatta
      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.
      (18 votes)
  • blobby green style avatar for user huy.ngo
    Question: Where does the ATP come from?
    (12 votes)
    Default Khan Academy avatar avatar for user
  • 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)?
    (5 votes)
    Default Khan Academy avatar avatar for user
  • duskpin ultimate style avatar for user moonchicken123
    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?
    (8 votes)
    Default Khan Academy avatar avatar for user
    • female robot grace style avatar for user tyersome
      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.
      (6 votes)
  • hopper cool style avatar for user SofiyaMarkova
    is ATP polar?
    (7 votes)
    Default Khan Academy avatar avatar for user
  • marcimus pink style avatar for user sgarner2025
    this stuff is really intresting
    (8 votes)
    Default Khan Academy avatar avatar for user

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.