Talk:Gluconeogenesis
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[edit] Disputed Image
I'm no specialist, so have not edited. Cannot gluconeogenesis also be caused by excess and/or too rapid protein intake? MIchael 07:56, 24 July 2006 (UTC) Douglas Michael Massing
The diagram "showing" gluconeogenesis is actually of glycolysis. This is a significant error and needs to be changed. Here is a very brief illustration that provides a better overview of gluconeogenesis.
--Dbrouse 00:02, 17 August 2006 (UTC)
The above illustration is a terrible instance of gluconeogenesis. The only problem with the diagram in the main article is its lack of distinction with glycolysis, which could be facilitated by the addition of enzymes.
By "terrible" - I am assuming that you are meaning that the illustration I provided as an idea is missing the detailed steps of metabolism. Note that I never proposed it was appropriate for the article page. If my interpretation of your meaning of "terrible" is wrong, please reply what it is about the illustration that is terrible. The illustration I submitted to this discussion page was created to show that the concept of gluconeogenesis really is NOT just a reversal of glycolysis. Glycoylsis is the metabolic pathway that converts 1 glucose into 2 pyruvates. Gluconeogensis represents the pathways that allow for new glucose to be made from glycerol, and some amino acids. Gluconeogenesis does utilize a pathway that can be thought of as a reversal of glycolysis but it is MORE than that.
My experience has been that biochemists have a tendency to think of gluconeogenesis as a reversal of glycolysis -- with a few modifications. (Berg,Tymoczko, & Stryer, Biochemistry, fifth Ed - online via Entrez Bookshelf) But physiologists, and others who study metabolism at the systemic and organism levels have a broader view of gluconeogensis. (Guyton & Hall, Textbook of Medical Physiology, 9th Ed.)They have a tendency to ALSO include the triglyceride mobilization from adipocytes and utilization of amino acids as part of overall process of gluconeogenesis. This is probably because at the organ/system/organism levels of organization it is important to understand how the different tissues and organs are regulated to provide the raw materials to make the new glucose.
Anyway, I notice that the diagram that initiated this discussion has been removed from the article page. If someone has an appropriate diagram that includes the broader view of gluconeogenesis, it would be great to have something to look at. I think that the broader view, that I have attempted to describe, should be used as it better represents dictionary definitions of gluconeongenesis (I looked at several including Tabers 20th ed.) and it INCLUDES the narrower veiw (reversal of glycolysis with modifications) of gluconeogenesis that is used by some groups of people. I could always request that my students help me make a new diagram for Wikipedia when we study metabolism next term... I hope it doesn't come to that because I have been known to make terrible illustrations. :-) Dbrouse
The diagram in the main article does illustrate a very vague gluconeogenesis route. No enzymes are shown. However, the Gluconeogenesis pathway is similar to the reverse of Glycolysis except for the use of four different enzymes (Pyruvate carboxylase, Phosphoenolpyruvate carboxykinase, Fructose-1,6 bisphosphatase, and Glucose-6 phosphatase) which is why they look similar. You can see the Gluconeogenesis route on the right of the pathway but a better diagram should be used to see the enzymes used.
-AndyKarlesky
[edit] Dispute
The accuracy of this article is disputed as the diagram shows glycolysis and not gluconeogenesis. The reverse reactions of glycolysis (shown in the image) can cause "new" glucose to be formed from small metabolites but there is more to gluconeogensis than just a reverse of glycolysis. Glycerol, from lipids, and deaminated amino acids are the major raw materials for forming new glucose.—Preceding unsigned comment added by Dbrouse (talk • contribs) Moved from article --Wafulz 05:38, 22 October 2006 (UTC)
i concur
- Mike Brubaker, Whitman College
[edit] When gluconeogenesis occurs.
The article implies that gluconeogenesis only occurs during starvation or intense excercize. This is quite misleading. Gluconeogenesis is an ongoing process in the body and not isolated to specific stresses. It is essential to reuse the lactate that accumulates during excercize back into pyruvate and then into glucose. It is also the major route for glycerol metabolism. It is an important biological pathway for many other purposes.
[edit] No futile cycle?
In the statement concerning the existence of a futile cycle, the article implies that glycolysis and gluconeogenesis are independent processes. This is an unfortunate conceptual error in understanding of the regulatory mechanisms of the two pathways. Both processes DO occur at the same time; thus, a futile cycle is continually in effect to a certain degree. The key is that one pathway is upregulated while the other is inhibited depending upon the given physiological state (ie. the presence of glucagon, insulin, epinephrine, etc). The cellular benefit gained from allowing the seemingly wasteful futile cycle is that it allows a very rapid response by hepatocytes (kidney cortex, too) to systemic change in serum glucose levels...a very good thing indeed if one is being chased by an angry lion!
If there are no disputes, I will come back and make the corrections with appropriate citation.
Awbacon 05:12, 8 September 2007 (UTC)
- In my reading of it, it doesn't seem to imply separate cycles. A futile cycle, however, would be when both pathways are operating at their full ability (thus negating each other physiologically). While both are continuously running, the inhibition of each cycle on the other through the three regulatory enzymes prevents it from becoming actually "futile". Schu1321 (talk) 07:41, 12 May 2008 (UTC)
[edit] WikiProject class rating
This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 16:27, 10 November 2007 (UTC)
[edit] New image, editing
I added a new image I made for the article and also reworked a large amount of the article text. I have the original image and can make changes easily, so if you notice any errors feel free to let me know and I can upload a revision. Schu1321 (talk) 07:43, 12 May 2008 (UTC)
