Talk:Glycogen

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edit·history·watch·refresh Stock post message.svg To-do list for Glycogen:
  • Reference
  • Compare
    • glycogen with starch in plants, and explain why glycogen is more effective for animals and starch more effective in plants.
    • glycogen storage with that of fats - a little more on how fats store the majority of calories and contain more energy per unit weight, but aren't as effecient when energy is needed quickly. Also mention that excess food is stored in adipose tissue once glycogen stores are maximized.
  • Larger summaries of the breakdown and synthesis
  • How many grams of glycogen in the body (~130 g in muscle, 70 in liver)
  • Explain why glucose can't be stored in its raw form
Priority 3

Several questions[edit]

Why convert glucose to glycogen? Size? How many calories are stored in the glycogen reserves of an average, healthy human? How long will this last during excercise, and will there be a noticable decline in performance once fat reserves are called upon? Is fat converted to glucose preemptively, before it's needed? Twilight Realm 22:23, 27 October 2005 (UTC)

The answer to the first question is that there are people who cannot synthesize glycogen. They have glycogen synthase deficiency and it causes hypoglycemia. There are far fewer calories stored as glycogen than as body fat. Carbohydrates like glycogen contain about 4000 calories per kilogram. Fats like adipose tissue contain about 9000 calories per kilogram. As an average adult liver weighs around 1.5 kg, and the glycogen content is probably less than half of the weight, there are maybe 2000-3000 calories worth of glycogen in your liver. The amount of glycogen in muscle and kidneys may be another kg at most. In contrast, if you have only 10 kg (22 lbs) of extra body fat, you have at least 90,000 calories stored in reserve. Some types of muscle contraction capacity decline as muscle glycogen is consumed. Fat is converted to glucose as it is needed, by shifts in hormones in response to shifts in glucose supply and other changes. alteripse 02:13, 28 October 2005 (UTC)
Thanks. These are all things I think should be included in the article, if you didn't add them already. What I wanted to know in my first question was why glucose isn't just stored as glucose in cells. Do you know? Twilight Realm 00:06, 3 November 2005 (UTC)
I thought I answered it by explaining that there is a disease where glycogen cannot be synthesized, and therefore there is no place to put the glucose. What are you imagining as a storage form for glucose if not glycogen? Glycogen is nothing but chains of ready-to-use glucose. If you are asking why the cells cannot hold enormous amounts of loose glucose, that would be the same condition as diabetes: too much loose glucose in the cell causes all kinds of problems. If you are asking why there aren't "bags" of sequestered glucose in the cells, I can't see why that would be an advantage. It's like asking why don't our mouths open directly into our stomach. This just happens to be the way our bodies work. alteripse 00:17, 3 November 2005 (UTC)
I see. So glycogen is completely ready to use, and the hydrolysis into glucose has no significant or inconvenient time delay or other disadvantage? Twilight Realm 21:33, 3 November 2005 (UTC)
Fat is never converted to Glc, not at least in humans according to the textbooks. Boris 13:55, 30 November 2005 (UTC)
I think this is correct. I should have said that fat is converted to ketones, a fuel which can be used by many tissues as an alternative to glucose. Glucose can be converted to fat, but there is no direct path the other way. alteripse 23:20, 30 November 2005 (UTC)
Let me add few things. First, Glc enters/leaves the cell through a proces called facilitated diffusion. Which means that as soon as the Glc concentration inside the cell is somehow increased, Glc will start leaving the cell - which by the way happens in hepatocytes during glycogenolysis. Second, even if there was a way to keep Glc inside the cell, say through active transport, Glc poses a danger to the cell integrity as Glc is a highly osmotically active compound. The cell solves these two issues with a single solution by synthesizing glycogen from Glc - the enormous glycogen molecules can't leave the cell, and by having osmotically inert glycogen instead of Glc, the cell avoids the osmotic shock. Boris 13:55, 30 November 2005 (UTC)
However Glycogen is still soluble in water. the article states "insolubility" (in the section about glycogen in muscle.Kosmologie (talk) 09:37, 17 July 2013 (UTC)

The article says that glycogen is called "plant starch". That's a mistake, isn't it?D021317c 05:17, 13 December 2005 (UTC)

Yep, you are right. I guess they ment "animal starch". Anyway, the whole article needs major work, honestly if you hadn't pointed the mistake out i would not have read it anytime soon. I'll see if i can edit it today. Boris 14:00, 13 December 2005 (UTC)

What is the relation of this with the liver which has become too fatty and bigger than the normal ? What this may indicate to and is this a reversible process and if yes how ? user:Infohnbc

Fatty liver, also called hepatic steatosis or less often steatohepatitis, is a complication of many different metabolic conditions and diseases, including obesity and poorly controlled diabetes mellitus. There is some evidence that in at least some cases it can be associated with progressive fibotic damage (cirrhosis) leading to liver failure, few people actually reach that point, but more often succumb to other complications of the same condition that produced the fatty liver. The natural history of the common forms of hepatic steatosis is not well understood; it seems likely that the process can be slowed or perhaps reversed by improvement of the underlying disease. alteripse 18:52, 26 December 2005 (UTC)
Tha'z very informative but is thea any link between this condition and any abnormal glycogen metabolism in the liver? Tha'z what, i believe, Infohnbc asked. -- Boris 19:25, 26 December 2005 (UTC)
I had no idea what he/she meant by "this" so I ignored it. You took it to mean "abnormal glycogen metabolism". Several tertiary sources list glycogen storage diseases as possible causes of fatty liver, but I couldn't quickly find primary or high-quality secondary sources to confirm it. alteripse 21:22, 26 December 2005 (UTC)

I have no idea how to use wikipedia but I was looking at the first picture on the page and I think it is wrong.

There is an extra carbon represented on either side of the alpha 1,4 linkage. I think this is wrong. Could someone fix it? -Andrew —Preceding unsigned comment added by 168.105.213.41 (talk) 06:14, 16 April 2008 (UTC)

carbohydrate loading[edit]

I am a college student and I am writing a paper on the effects of carbohydrate loading on performance. What exactly happens (on a physiological level) when dietary carbohydrate intake is significantly increased? What happens to the excess stores of glycogen?

Mostly what happens is that once the liver and muscles are full of glycogen, excess glucose is used to synthesize triglycerides, and the triglycerides are stored as adipose. alteripse 11:04, 30 November 2005 (UTC)

The idea that adipose tissue only stores blood glucose as fat after the muscles and liver have had their fill is not correct, at least after the 1st hour following secession of exercise. (1hr, or, perhaps an interval equal to that of the preceding exercise. The research seems to be in flux here) The reason it's important when carbo-loading to ingest low GI foods, v.s. high GI foods, is because blood glucose levels in excess of the conversion rate by the liver, and then the muscles (I believe the liver must be fully restocked before muscle glycogen repletion commences - at least according to John Forrester) must be absorbed by adipose tissue and stored as fat to prevent hyperglycemia. This a proper functioning of adipose tissue in healthy humans. It should also be noted that protein in amounts greater than the body's current use, and some small storage amount, is converted to glucose, and at a rate that makes it a low GI food. Therefore, ingesting some additional protein, a "fudge factor" for protein if you will, is a good way to "carbo-load", even though it is not a carbohydrate. --Solidpoint (talk) 01:02, 28 July 2011 (UTC)

I think this is useful in forming a link as to the cause of a fatty liver.Am I right in thinking that the formation of fatty voids in the liver starts with triglyceride cells?

From what I understand, the main reason for carb loading is to make sure you have fully loaded muscles, even though this necessitates overestimating it to put on a little fat. Endurance athletes tend to watch the diet so that while they have energy for training, they remain pretty lean, even if that does occasionally mean slightly reduced performance on training days by having slightly sub-maximal glycogen reserves, but this can't be afforded when you are peaking for training. By having low body fat levels, it doesn't matter if they do overestimate it a bit. Tyciol 12:38, 31 December 2006 (UTC)

Biochemistry[edit]

Glycogenesis and glycogenolysis have their own articles, so how are we going to do it with the raections - add them to "Glycogen" with links from these two articles pointing to it, or the other way around - the links here in Glycogen and the explanations in "Glycogenolysis" and "Glycogenesis"? I think they should be here because their regulation is very tightly linked, very. Boris 20:20, 14 December 2005 (UTC)

why glycogen[edit]

The reason cells store energy as glycogen is because it has a MUCH lower osmotic effect than the single glucose molecules :) 195.93.21.8 18:53, 8 May 2006 (UTC)

Then find a reference that says that and add it to the article. Richard001 04:02, 25 May 2007 (UTC)

Glycogen storage limits and modifications[edit]

"Due to the body's ability to hold no more than around 2,000 kcal of glycogen"

The article says something to this effect. I think we will all agree that there would be genetic differences as to the size of the liver and muscles (probably somewhat proportionate to height and other size factors) which would modify this amount. There would probably be some sort of comparative ratio, varying for ideality.

What I am curious is... are we sure that the maximum glycogen stored in any specific area cannot be safely increased by training? Training obviously involves some sort of drainage, though I wouldn't know what. I am unsure how one would increase glycogen storage in the liver, whatever it would be, it would be more of a response to overall training loads, so it's best not to mind it. What I am curious about is the glycogen storage in the muscle tissues. When a muscle grows, be it multiplication of the contractive proteins (called myofibrilar hypertrophy) or the ability to expand them to let in more fluid (sarcoplasmic hypertrophy), in either case the muscle grows.

To reach greater amounts in size in either case, a muscle is exposed to overload. Overload would deplete glycogen stores at increasing speeds depending on resistance, and increasingly lower % based on volume. As the other tissues expand when a muscle grows, would it be unrealistic to assume that the muscle glycogen storage capacity also grows with it? With this, it also means that muscles would be able to exert more force without forcing the liver to release glycogen so that they can draw on its sugars. That would mean more glycogen can be held in the liver for more critical functions like the brain, or other organs. I think the point of forcing the liver to help out is what causes modifications in muscle size, even though I don't know why.

Of course, much of increases in endurance may just be due to a more efficient lactic acid uptake combined with better VO2 max for better aerobic energy production, so it may not be necessary for glycogen stores to increase at all, but mass is mass, even if fuel, so that would be interesting.

It might also explain why sometimes people's muscles are 'flat' when they're tired and depleted. Tyciol 12:47, 31 December 2006 (UTC)

WikiProject class rating[edit]

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 07:54, 10 November 2007 (UTC)

main picture is wrong[edit]

so the first picture to the right, that shows the structure of glycogen, is wrong as it shows an extra carbon branching of the pentose ring. the oxygen atom should be drawn directly to the 1st carbon on one ring to the 4th carbon on the other, there is no ch2 group off the ring. —Preceding unsigned comment added by 190.22.9.228 (talk) 08:54, 26 April 2008 (UTC)

Yes, I was wondering why this was. I looked in my human biochemistry textbook (Mosby), it is wrong in there also. I have various organic texts in my office (I am an Organic Chem Prof.); they get it right. I find it correct and incorrect on various sites on the internet. Glycogen is a polymer of glucose formed from mostly 1,4-α-glycosidic linkages. The carbohydrate polymer does not have ether functionality depicted in the Wikipedia page. I am going to attempt to switch out this picture. ArthurCammers (talk) 17:48, 19 September 2014 (UTC)

Animal starch?[edit]

The lead states that glycogen is "commonly known" as animal starch. I agree with the analogy but I have never ever heard/read anyone using the term. If theres no proof to the contrary I'm going to reword it. Sahmejil (talk) 09:07, 6 October 2009 (UTC)

Poor opening line[edit]

The article currently starts with "Glycogen is the molecule that functions as the secondary long-term energy storage in animal and fungal cells ... "; but I can't see anywhere where it tells us what the primary long-term storage is - if I knew, I'd add it, but I would have thought glycogen was, and unfortunately the reference for this sentence is a book so we can't check what it says. --jjron (talk) 08:24, 27 April 2011 (UTC)

Oh, maybe in this sense fats would be being regarded as the primary storage? Definitely not at all clear. --jjron (talk) 08:26, 27 April 2011 (UTC)

OK, have added in that fats (adipose tissue) are the primary energy storage, just so it makes some sense. --jjron (talk) 00:24, 28 April 2011 (UTC)

Wouldn't this only apply to animals though? I may try and reword this sentence later. -Zynwyx (talk) 22:55, 11 June 2012 (UTC)

Glycogen debt vs Glycogen depletion[edit]

I have changed the heading because "debt" implies you have none left, but you can borrow some. It also obscures that you started with a fixed store, it is being used up, at some point it will be depleted, and there is no mechanism to borrow some from anywhere in the body. --Solidpoint (talk) 01:07, 28 July 2011 (UTC)

Chain linkage types[edit]

The second paragraph states "Glycogen is a polymer of α(1→4) glycosidic bonds linked, with α(1→4)-linked braches" but surely the chain linkages and the branch linkages are different types; I suspect that the latter part of this statement should read "with α(1→6)-linked braches" since the side branch attaches to the 6 position. 216.58.38.82 (talk) 03:34, 12 September 2011 (UTC)

Ways to fight glycogen depletion[edit]

There is a problem in the paragraph "Glycogen depletion and endurance exercise": It claims that "Glycogen depletion can be forestalled in four possible ways". but then only lists three.

Is one missing, or should it say "three possible ways"?

Whiterabbit fr31 (talk) 08:06, 9 December 2011 (UTC)