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Co-factors, co-enzymes, and vitamins

Co-factors and co-enzymes assist enzymes in their function. We will learn what both co-enzymes and co-factors are, and how they might affect the catalysis of a reaction. By Ross Firestone. Created by Ross Firestone.

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  • old spice man green style avatar for user maham malik
    what is apoenzyme and holoenzyme?
    (14 votes)
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  • piceratops seedling style avatar for user Emilee Paige Demaray
    What is the actual definition of "organic"?
    (4 votes)
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  • blobby green style avatar for user Huan Nguyen
    Are co-factors and co-enzymes considered enzymes?
    (5 votes)
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  • blobby green style avatar for user Bukubacaleb
    how to increase testosterones level in your body
    (1 vote)
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  • leaf yellow style avatar for user adamzalaquett
    What type of biological molecule category would co-factors and co-enzymes fall under? are they a mix?
    (4 votes)
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    • leafers sapling style avatar for user yasminhooman
      Both are non-protein molecules that can be organic or inorganic helpers of proteins (they are not necessarily always helping enzymes but often do). All coenzymes technically are also cofactors but not all cofactors are coenzymes. Co-enzymes are usually loosely bound and organic. Subcategories such as prosthetic groups (ex. Heme) refer to how tightly bound the cofactor is. Prosthetic groups are tightly bound usually via covalent bonds. The term cosubstrate means loose/diffusible and needed in stoichiometric amounts.
      (6 votes)
  • hopper jumping style avatar for user Jacob Anderson
    Is NADH a substracte or Co-enzyme just based on the perspective taken?
    (2 votes)
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  • mr pants teal style avatar for user Robin Sutcliffe
    at Mg2+ is shown to be stabilising a molecule of DNA. It was shown to be stabilising 3 negative charges on the molecule, however there is only two positive charges on the magnesium, how is it able to balance three negative phosphate ions?
    (3 votes)
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  • blobby green style avatar for user kjhart91
    Isn't iron in hemoglobin a co-factor, that simply acts as a carrier of oxygen? Is it accurate to say that a distinction between the two is that co-factors don't act as just carriers?
    (2 votes)
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    • leaf blue style avatar for user Kevin D. Fettel
      Some sources, like here, limit the use of the term "cofactor" to inorganic substances only. Others divide cofactors into several subgroups that becomes more all encompassing.

      Cofactors can be subdivided into either one or more inorganic ions, a complex organic or metalloorganic molecule called a coenzyme.

      The iron in heme acts as a prosthetic group. Heme is therefore sometimes referred to as a Metalloprotein. Metalloprotein is a generic term for a protein that contains a metal ion cofactor. You'll see characteristics of both coenzymes (organic) and cofactor (inorganic) attributes. Not necessarily one or the other.

      Hope this helps.
      (3 votes)
  • leafers ultimate style avatar for user Joseph Frimpong
    This video never clarifies that cofactors and coenzymes are non-protein by definition. This actually shows up in one of the questions for this section.

    Also, this video give the impression that coenzymes and cofactors are different things, but coenzymes are a type of cofactor.
    (2 votes)
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    • leaf green style avatar for user Arno Arian Bashtar
      I agree with joseph, they should redo this video. Coenzymes should be classified as a type of cofactor, the same way BMW is classified as a type of a car. There are two types of coenzymes, cosubstrates (like NAD+) and prosthetic groups (like heme). Ref. Principles of Biochem textbook (moran et al.)
      (2 votes)
  • blobby green style avatar for user denae.heartfield
    Are cofactors/coenzymes considered allosteric regulators?
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    • male robot hal style avatar for user Jay Guyll
      Typically if a molecule is acting on an enzyme allosterically, it is not considered an co-factor, it would be considered a cell signaling molecule. Often times calcium is bound to an enzyme through a molecule known as calmodulin. This interaction alters the functions of proteins. Some examples of these interactions are found in the adenylate kinase or nitric oxide synthase pathways.
      (1 vote)

Video transcript

Today, we're going to talk about co-factors and co-enzymes and how sometimes they can be essential to proper enzymatic function. But first, let's review the idea that enzymes make reactions go faster. And they do this by lowering the activation energy peak of their respective reactions. Let's also review the idea that enzymes bind their substrates at a location on the enzyme called the active site, which is where most of the reaction takes place. Now, not all enzymes are able to catalyze reactions on their own. And some need a little help. So if we have our enzyme here, trying to react with our substrate over here, sometimes something called a co-factor or a co-enzyme will be needed, which will also need to bind to the enzyme in order for it to function properly. And we're going to go over what co-enzymes and co-factors are and exactly how they work. So first, we'll talk about what a co-enzyme is. Well, co-enzymes are organic carrier molecules. And what I mean by "organic" is that they're primarily carbon-based molecules. And by "carrier," I mean that co-enzymes hold on to certain things for an enzyme to make the catalysis run a little more smoothly. And a great example of a co-enzyme is NADH, which acts as an electron carrier. And here, I've shown NADH dissociating into its oxidized form, NAD+, as well as to a hydride ion, which basically just exists as a pair of electrons that some other molecule would be grabbing. So NAD+ can accept electrons, causing the molecule to be converted to NADH, which could then carry electrons for an enzyme. Now if you remember the lactic acid fermentation reaction, where pyruvate is converted to lactic acid, you'd see that the enzyme catalyzing this reaction, lactate dehydrogenase, uses NADH as a co-enzyme in order to transfer electrons to the pyruvate molecule, in order to turn it into lactic acid. And in this sense, NADH is acting as an electron-carrying co-enzyme. Another example of a co-enzyme is co-enzyme A, which like NADH acts as a carrier molecule. But instead of carrying electrons like NADH does, co-enzyme A, which we sometimes call CoA, holds on to acyl or acetyl groups instead. And you'd see CoA appear quite often in metabolic reactions, where it will carry these two carbon acetyl groups from one molecule to another. Now, co-factors are a little different from co-enzymes. While co-enzymes are only really involved in transferring different things from one molecule to another, co-factors are directly involved in the enzyme's catalytic mechanism. They don't strictly carry something like a co-enzyme would, but might be stabilizing the enzyme or the substrates or helping the reaction convert substrates from one form to another. A great example of this is with the enzyme DNA polymerase. Remember that DNA polymerase is responsible for helping out with synthesizing new DNA during DNA replication. Now, you may remember that DNA is a very negatively charged molecule because of all the negatively charged phosphate groups that you'll find around it. Well, DNA polymerase uses a magnesium ion as a co-factor, which can use its big positive charge to stabilize all that negative charge on DNA. And you can see how this is different from a co-enzyme. Becomes instead of acting as a carrier molecule, the magnesium ion co-factor is stabilizing the DNA and is more directly involved in the actual catalysis. Now, interestingly, what people normally called vitamin and minerals, like the kinds that a doctor would tell you to make sure you get enough of in your diet, are often different co-factors and co-enzymes. And what's special about vitamins and minerals is that your body can't build them up from scratch. And you need to get them from your diet in order to stay healthy. So when we say vitamins, we typically refer to organic co-factors and co-enzymes. So two great examples are ones we just discussed. Vitamin B3, which you may see being called niacin on a food label, is actually just a precursor for NAD. And vitamin B5 is just a precursor for co-enzyme A. Minerals, on the other hand, are inorganic, meaning they aren't carbon based. And minerals are usually just co-factors in our body. So magnesium would be a great example of a mineral co-factor that an enzyme like DNA polymerase would use. Now, not all minerals act only as co-factors. Some minerals, like calcium, which can act as a co-factor, is also a critically important component of bone and teeth. And it doesn't strictly act as an enzyme co-factor here. It's actually an important part of the structure itself. So what did we learn? Well, first we learned that not all enzymes are able to function alone and some need a little help. And next, we learned that this help can come from co-enzymes, which usually act as carrier molecules, or co-factors, which directly assist with the catalysis that the enzyme is doing. And finally, we learned that the vitamins and minerals generally refer to dietary co-factors and co-enzymes.