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Pyruvate is used in Krebs cycle and oxidative phosphorylation to generate most of the ATP required.

Isn't it more direct to use pyruvate in IV drip compared to glucose? Also, we will only lose 2 ATP and 2 NADP if we use pyruvate instead of glucose through glycolysis?

Is it due to the production and storage cost of pyruvate? Does pyruvate "degrade" faster than glucose?

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  • Does pyruvate occur naturally? If there isn't any benefit to using pyruvate as opposed to glucose (it only gives more energy for the same mass, and glycolysis doesn't take much time compared to the Krebs cycle and the ETC), and if it takes effort to make pyruvate (I don't think it occurs naturally), why not just use glucose which occurs naturally in quite abundant amounts? In asking why pyruvate isn't used in IV drips, maybe you should consider why pyruvate should be used. That will help us see if there is any potential benefit to using pyruvate instead of glucose. – Zo-Bro-23 Feb 06 '23 at 07:55
  • I would not advise you to make suggestions for medical procedures based on the knowledge of biochemistry your question reveals, but if you are determined to do so, SE Medical Sciences would be a more appropriate place. However before posting I would clarify your vague concept of "direct" and research the purpose of a IV drip. The Wikipedia article suggests the importance for hydration and salt balance as well as substitution for normal blood nutrient, glucose. How is pyruvate intended to substitute for the latter in brain and red cells? – David Feb 06 '23 at 11:59
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    @David - There may well be a role for pyruvate (NaPyruvate) in IV drips for patients with sepsis, or in resuscitation scenarios. It might even be a good fluid for rehydration. This question isn't as far fetched as it seems to you. The IV fluids we have are far from ideal for every situation and are used mainly because of familiarity. – anongoodnurse Feb 06 '23 at 14:25
  • @Zo-Bro-23 - Where does glucose occur "naturally in quite abundant amounts?" – anongoodnurse Feb 06 '23 at 14:39
  • @anongoodnurse this webpage lists some sources. Starch would be an obvious answer, and sugar contains glucose too. Honey contains glucose monosaccharides in some amount. While it glucose may not occur naturally in a usable form, it is relatively easy to extract glucose from these various sources, and commercial glucose production is quite viable (an obvious example is the glucose used for IV drips). Pyruvate seems much more difficult to isolate and produce, and its natural abundance is low compared to glucose (please correct me if I'm wrong!). – Zo-Bro-23 Feb 07 '23 at 03:44
  • @Zo-Bro-23 - Glucose (alone) is not "quite abundant". Sucrose is, starch is, etc. but glucose has to be derived. Just because it's used in IV's (as dextrose) doesn't mean it's "quite abundant (naturally)". Lots of things that aren't abundant are used in IVs, like inotropes, etc. My point is that you were fairly aggressively challenging the OP when you didn't seem to know all that much yourself. – anongoodnurse Feb 07 '23 at 04:05
  • @anongoodnurse got it! While that wasn't my intention (I was asking the OP a genuine question), I'll be more careful about my tone in the future. – Zo-Bro-23 Feb 07 '23 at 13:13
  • @Zo-Bro-23 - Thank you for the gracious response. It's hard to get the intended tone from the written word, so it's easy to misinterpret genuine concern for criticism, especially to the OP, so I find it better to err on the side of a softer approach, but that's just me. I'll delete my comments to you once you've read this (let me know.) Again, thanks. – anongoodnurse Feb 07 '23 at 13:43
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    @anongoodnurse I agree! It's especially easy to misunderstand someone's tone or intention on a text-based forum like this. I should be more careful about how I phrase my responses in the future.

    You needn't delete your comments; it might be useful for someone else in the future. Thanks for your courteous response. Cheers!

     – Zo-Bro-23 Feb 10 '23 at 09:28

1 Answers1

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A really nice question! Many organisms are capable of taking up glycolysis or Kreb's cycle intermediates and feeding them into their respective pathways. Therefore it feels natural to ask why humans can't do the same with pyruvate. While I cannot find a precise answer, I will do my best to argue why it isn't the wisest to swap in pyruvate in place of glucose.

  1. Transport: Molecules like pyruvate and glucose do not diffuse very well across lipid bilayers and need specific transporters. All cells have abundant glucose transporters on their surfaces that enable glucose uptake. Pyruvate can be transported into cells via monocarboxylate transporters [1]. In general, I would assume that most cells are better adapted to take up glucose from their environments than pyruvate, although I cannot find evidence to substantiate this.
  2. Glycolysis is important! Glycolysis does more for the cell than just breaking down glucose to pyruvate. Many intermediates feed into other pathways, and many pathways can feed into glycolysis through them. It is an important metabolic junction. Skipping glycolysis would deprive the cell of that metabolic branching. Take a look at [2] to see how glycolysis connects with some other metabolic pathways.
  3. Energy loss: 2 ATP and 2 NADH add up to about 8 ATP lost. May seem like a small amount, but it adds up.

Biochemistry aside, some points raised by the comments here as well are valid: glucose is easy to manufacture or isolate, while pyruvate isn't. If the wheel isn't broken, don't fix it!

[1]https://en.wikipedia.org/wiki/Monocarboxylate_transporter

[2]https://www.researchgate.net/figure/Landscape-of-glycolysis-and-its-associated-metabolic-pathways-Schematic-representation_fig1_319159257

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    "If the wheel isn't broken, don't fix it."I would have upvoted this but for that last statement. It might be round, but how do you know it's the proper wheel? If we didn't search for better alternatives, we will never find something even better. There are so many examples in medicine of accepted/"best" practice being turned upside down by one person questioning the status quo, my favorite example being Dr. Barry Marshall. How many millions of people whose lives he made much better we'll never know. (Had he made his discovery 10 years earlier, my mother might still be alive.) – anongoodnurse Feb 07 '23 at 13:53