ATP hydrolysis mechanism
ATP hydrolysis mechanism. How energy is released when ATP is converted to ADP and phosphate.
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- Is the ATPase Sal refers to the same as the ATP synthase I was taught, or are those two different enzymes?(28 votes)
- The ATP synthase sal talks about is an enzyme which synthesizes ATP by combining ADP and free phosphate group. ATPase is an enzyme which breaks down ATP into ADP and free phosphate group.(9 votes)
- What does nucelophillic mean?(10 votes)
- Its means "nucleus-loving", something that is drawn to positive charge of the nucleus, in other words nucleophiles tend to be negatively charged molecules.(21 votes)
- Is ATP the only form of usable energy?(8 votes)
- Guanosine triphosphate (GTP) is a source of energy in some protein synthesis reactions and gluconeogenesis.
Uridine triphosphate (UTP) is another source of energy, but very specific and as far as I know it is used only in metabolism of galactose.
And, finally, I think cytidine triphosphate (CTP) can also be used as an energy source in some reactions, but that's for someone else to check.(14 votes)
- In the drawing on the left, from what I understood it shows the hydrolysis of ATP to form ADP (I hope that is correct so far).
The water molecule has two H atoms, and after hydrolysis, one of them is added to the single phosphate group. But where does the other H atom go? It doesn't seem to be connected to the other 2 phosphate groups.(5 votes)
- The Hydrogen atom leftover has a positive charge. Water molecules are electronegative (hog electrons), so the water molecule will snatch up the Hydrogen atom thus forming Hydronium, or H30.(6 votes)
- What other molecule can perform a nucleophilic attack on ATP and thus, cause hydrolysis?(6 votes)
- Most ATPase's can use nucleophiles such as OH groups on amino acids to attack the phosphate group, this page is quite useful although is requires a bit of biochem background http://biowiki.ucdavis.edu/Biochemistry/Oxidation_and_Phosphorylation/ATP_and_Oxidative_Phosphorylation/Properties_of_ATP(2 votes)
- At approximately1:25Sal mentions things other than water can perform hydrolysis. What are those other things and is it still called hydrolysis?(4 votes)
- Hello Mary, some other polar solvents are also able to do this; it is generally called solvolysis.
Some of this processes have an own name, so hydrolysis with water, alcoholysis with alcohol, ammonolysis with ammonia and aminolysis with alkyl amines.(4 votes)
- at2:53, where did the original oxygen that was in the phosphorus go? if the white oxygen represents water's oxygen.(3 votes)
- the second phosphate group took both the electrons in the bond therefore keeping its oxygen to itself.(1 vote)
- How does a chemical reaction utilize the energy released from ATP?(3 votes)
- When ATP releases a phosphate group and attaches it to a protein or some other molecule it changes its shape, allowing it to do work in the process. Also phosphorylation (adding a phosphate group) to a molecule helps certain reactions by giving them enough energy.(3 votes)
- In the graph on the right, wouldn't it still need an investment in energy for the reaction to occur? So even with a catalysis, there still needs to be an investment but a smaller investment than that without a catalysis?(3 votes)
- the energy is provided by body heat(1 vote)
- what happens to the other hydrogen?(2 votes)
- It combines with the other water molecules to form a hydronium ion(3 votes)
- We've talked a lot about ATP being the energy currency of cells, but I want to dig a little bit deeper into that in this video. And as we'll see when we go from ATP to ADP, ADP + a Phosphate group, we have a release of free energy. If we look at just the system, ATP's free energy is over here, but once hydrolysis has taken place and now it's ADP + a Phosphate group, the free energy has dropped by roughly 30.5 KJ/mol our Delta G is -30.5 Kilojoules per mole and if you watch the videos on Gibbs Free Energy this tells us that this is a spontaneous reaction. Delta, Delta G is less than zero, which tells us that this is going to be spontaneous. Now when I first learned this I was like, well if it's going to be spontaneous why wouldn't all of the ATP just spontaneously and all of the water turn into ADP and just release it's energy as heat or whatever else? And the key is, it has to get over this hump. You have this activation energy, it has to go uphill a little bit if there's no enzyme to catalyze it. And the reason why we have this uphill hump is the way that ATP gets broken up is that you have to, if we're talking about a water molecule doing the hydrolysis which is typically what people think about hydrolysis, although it can sometimes be done by a different molecule, if you think about the water molecule what needs to happen is, you need this lone pair of electrons on this oxygen to be able to do what we call a nucleophilic attack on this Phosphorous in this phosphate group and if that happens, it forms this bond and then these electrons can be taken back by this oxygen which gives its negative charge right over there. Now you might say, "Okay, this makes a lot of sense", but you have to rememeber this, electrons are negative and they're surrounded by these negative charges. So they have to overcome getting close to these things so as they're approaching these negative charges, they want to repel each other, so you have to overcome that. And the way that it's overcome is a class of enzymes called ATPases, ATPase. And what they do is, remember these enzymes are these big protein complexes and the ATP molecule combined in the right place. And they essentially try and surround the ATP molecule with some positive ions. So let's say there's a positive ion here. So it can keep these electrons busy while the water, or whatever is doing the nucleophilic attack, can not have to worry about these electrons over here. So it might have a positive ion here. And remember, if we think in three dimensions, this thing is all wrapped around in different ways around the ATP molecule, so this is the ATPase. And so by having the enzyme over here, you're lowering the activation energy. And so it might end up looking something more like this. And so the reaction can actually occur. So the reason why you don't just see this happening all the time without an enzyme is why you have to overcome this hump. But once you have the enzymes they can actually allow the reaction to occur. So this attacks this, forms this bond, and then you say well, "You have another hydrogen right over here, you have another hydrogen right over here." But this could get nabbed up by another water molecule becoming a hydronium ion, which is actually what's going to happen. And then, this character takes away this pair of electrons, becomes a negative charge, and we're left with that Phosphate group has been broken off and then we have our ADP and we have our release of energy. Now, typically you don't want this to release energy for no good reason. Most ATPases are going to leverage that energy that release this reaction to phosphorylate a molecule. And in this case you can kind of think that this hydroxide has been phosphorylated, but it might phosphorylate something else. Or it might change the confirmation of this ATPase so it can do some other type of work, transfer molecules against their concentration gradient or chemoelectric gradient, whatever it might be. You don't want to just release the energy. Sometimes it might happen if you just want to generate some heat, but usually you're going to do some useful work for the actual cells. Hopefully this gives you a little more appreciation for ATP and the reaction by which the hydrolysis can occur. This is called hydrolysis because, at least in this example we're using a water molecule to break it up or to take off a phosphate group.