Nutritionally, proteins come in two forms: complete proteins contain all eight of the essential amino acids while incomplete protein is missing at least one. The human body requires 14 other amino acids, which it can synthesize from the essential amino acids. Animal-derived foods contain all of those amino acids, while plant sources do not. That is why vegans must mix their protein sources. Ovo-lacto vegetarians usually do not have this problem, since egg's white and cow's milk contain all essential amino acids, as well as soy milk.

If soy contains all esential amino acids, and the 14 other amino acids can be synthesized from the essential amino acids, then why do vegans need to "mix their protein sources?" 09:31, 15 Oct 2003 (UTC)

Capping protein molecular weights at 100,000 is way way underkill. Multisubunit proteins can go a lot higher than that. Polymerized hemoglobin S has an aggregate molecular weight in the millions (I won't even get into such multisubunit freaks as worm oxygen carrying pigments), and what about the molecular weight of a blood clot? -- David M

Ok, if protein engineering is the field of playing with proteins after the genetic component, doesn't that lead to confusion with those researchers who were and are involved in de novo protein design, such as the Dickersons of Duke? - Dwmyers

This article has a good, systematic description of proteins. However, as this article should be interesting to the layman, we should start by indicating why proteins are important (nutrition and funciton in biology). I'll get started on this. -adam

One can go to far with this kind of thinking. It might be that for most people mustangs are a kind of car, but that's not the subject with which I would want to begin a general article on mustangs. Actually, maybe it's a mistake to try to make an all-purpose protein article. How about a separate one called Protein (nutrition)?168... 19:58 2 Jun 2003 (UTC)

I'm going to go ahead and do that (separate the content into two articles, one called Protein (biochemistry) and one called Protein (nutrition)) unless people strenuously object or I hear a good reason why not. 168... 02:46 4 Jun 2003 (UTC)

Muscle Fibers

The page on proteins says: "For example, muscle is composed of protein fibers, but these fibers have nothing to do with enzymatic reactions."

This is contrary to my understanding of muscle contraction and should be removed. ATP hydrolysis by the myosin, one of the proteins in muscle fibers, is an enzymatic reaction that directly contradicts that above statement.

Barry Hicks

You're right, at least so far as the way I use the mushy term "enzymatic." That error was introduced by an unregistered user. I changed it.168... 18:14, 20 Jan 2004 (UTC)
The author(s) who originally wrote the sentence or someone else who knows about the topic may not see your note or the mistake. If you know about this, you should feel free to make the necessary corrections. Dori | Talk 17:28, Jan 20, 2004 (UTC)

Title and disambiguation

I think it would be better for the primary article on protein to be the biochemical version (i.e. move protein (biochemistry) back to protein), and we can have a link to protein (nutrition) sense in a disambiguation section. In general if a word has one primary sense, it's best to have to primary article at that word, then then point to other one's in a disambiguation block. This way we would preserve the history of the current article. --Lexor 23:27, 20 Jan 2004 (UTC)

Here's the complete and single-sense definition of protein in the American Heritage Dictionary

Any of a group of complex organic macromolecules that contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur and are composed of one or more chains of amino acids. Proteins are fundamental components of all living cells and include many substances, such as enzymes, hormones, and antibodies, that are necessary for the proper functioning of an organism. They are essential in the diet of animals for the growth and repair of tissue and can be obtained from foods such as meat, fish, eggs, milk, and legumes.

So, according to the AHD, the primary and only sense of the word includes the significance of protein as a component of nutrition. As a former molecular bioscientist, I like you, think of proteins foremost as molecules and not as something to chew on or digest. But I think we are in the minority, and I don't see on what basis we could argue that what "protein" means to us is more important than what "protein" means to most people. To give over the article title "protein" to just one of its connotations is in effect to assert exactly that. Maybe no nutrio-centrists are complaining now, but we've seen this kind of complaining over Gaia theory, and I'd rather we just do this in a way that doesn't open such cans of worms. Although I had forgotten all about it, I noticed I brought this up in June and nobody had objected since, so I just went ahead with it today. User:Stewartadcock has already been at work chaning "protein" links all over Wikispace to "protein (biochemistry)" links. If we were to decide to undo the change of title, I wouldn't want to be the person to tell him.168... 23:44, 20 Jan 2004 (UTC)

Don't worry... it was only about 15 minutes work while I was waiting for some data to be processed. I, basically, just modified the links that went to Proteins a redirect page, rather than Protein -- so they probably needed changing anyway. Stewart Adcock 18:14, 21 Jan 2004 (UTC)
Sorry, I only notice your Talk comment from June 2003 just now, I don't think I had the article on my watchlist back then. It seems to me that protein in the biochemistry sense and the nutrition sense are really talking about the same thing underneath: protein molecules. Couldn't we simply have a nutrition section within the main protein article on nutrition. It just doesn't seem that they're different enough concepts to warrant separate articles, unlike, say, law: which has a scientific and a legal meaning? I suspect most people won't search for the two meanings when they link to protein, and so they'll have to go through another hop to get there, which sort of violates a common Wikipedia principle I've seen invoked: the principle of least surprise (this principle is mentioned in several places, but I'll be darned if I can actually find the link in the Wikipedia: namespace). --Lexor 01:21, 21 Jan 2004 (UTC)
PS, if we do decide to switch back, I'd be happy to undertake the link switching task. --Lexor 01:24, 21 Jan 2004 (UTC)
I'm attracted by your solution of putting the protein nutrition content into whatever larger article exists on nutrition, but after a moment of teetering I am back to favoring the tack I just took. My reasons are a) I think your proposed solution would require vigilance and enforcement, because the way nutrition info collected in the single protein article was just that people with stuff to say about it liked the thought of sticking it in an article with "protein" in the title, which is liable to happen again and again; and b)there's a lot that can be said about nutrition, and to require that everything nutritional that pertains to protein appears in a single universal nutrition article is in effect to hamper and perhaps limit the growth of both that article and nutrition content generally on Wikipedia. What do you think? Do you disagree? (generous of you to offer to change the links back BTW. Not an antidote to the feeling of wasted effort, but a pill sweetener for sure)168... 02:52, 21 Jan 2004 (UTC)
I still think it would be possible to have a protein nutrition section which could be more-or-less for nutrition oriented information, so long as its obvious. I still think that having the main article on protein and a separate protein (nutrition) would be relatively uncontroversial, but I'm happy with having a single article too. I don't think what's been done is wasted effort either because the hard work of separating the information has already been done. --Lexor 03:31, 21 Jan 2004 (UTC)
Also I notice that the current protein (nutrition) article already mentions aspects of the molecular nature of proteins that would make the most sense in the context of a full protein article. If there is a need for a more specialized article on protein in humans, we could create a link to a Main article: protein nutrition in humans or somesuch, and leave a brief summary in the protein article (cf. simulation and computer simulation for an example of this). In fact the more I think about, the more having a single protein article makes sense. --Lexor 03:35, 21 Jan 2004 (UTC)

I'm skeptical, in part because I'm not sure I understand what you have in mind. What would you think of creating a test page? --168...

Done, see User:Lexor/Temp/Protein. --Lexor 11:18, 22 Jan 2004 (UTC)

I don't object to an unlimited amount of nutritional info about proteins stuck at the bottom, but what originally got me on this hobby horse was that people were sticking it at the top, right after the intro 'graph. I'm not competent to edit the nutritional info, and with all the fad diets and nutty ideas available for promulgation, I could imagine the section bloating without limit as I stand helpless to edit out the chaff from the gluten and watch what I think of as most important sink lower down the page and away from their pertinent introductory remarks. At first blush, I didn't take to your idea of a protein nutrition in humans article, perhaps because of the title, but I think that could be the answer to my bloat fears. You didn't seem to think so, but I think it would be essential. So if you do go in for the idea of the text page, I'd like to see what you would pick as the minimal nutritional requirement for this article. Assuming it would be brief, I suppose it would be best at the top where there was a section before.168... 04:05, 21 Jan 2004 (UTC)

Putting everything regarding nutrition (but with a brief note of nutrition issues in the introduction) at the bottom would be fine with me. I think when it begins to get large or drift from talking about protein into diets and other more nebulous issues, then we could split off that information into another article. At the moment the information in the current protein (nutrition) would seem to fit comfortably in one article. --Lexor 04:16, 21 Jan 2004 (UTC)

Do you have an answer for the people who wanted that stuff up top, or shall we just hope they never come back again?168... 04:25, 21 Jan 2004 (UTC)

I think mention of role of protein in nutrition is entirely appropriate in the intro, just about as much as is included in the dictionary definition you cited should be enough. Where more details can be found will appear in the TOC which will appear immediately after the first 1-2 paras anyway. --Lexor 11:06, 22 Jan 2004 (UTC)

O.K., I like that fine (including the test page, which I visited), but remember when the revolution comes I'll be saying this was your idea.168... 04:11, 23 Jan 2004 (UTC)

Merge is complete, I've started switching links back, but got to go offline for a while. The number of links to the main protein article still dwarf the protein (biochemistry), protein (nutrition) ones, however, so it's not so bad. I put editorial comment about possible sub-article protein and nutrition in main article in HTML comment. --Lexor 04:37, 23 Jan 2004 (UTC)

There isn't a mention of Protein as a food in the intro at the moment. I think it needs to be there, regardless of the fact that links from nutrition related articles don't point here. How about starting the article "Proteins, one of the major classes of biochemical macromolecules ..." Richard Taylor

Proteins differ from Carbohydrates...

Proteins differ from carbohydrates chiefly in that they contain much nitrogen and a little bit of sulfur, besides carbon, oxygen and hydrogen

I'm not sure that I like this sentence. It seems to infer that a protein is a carbohydrate with nitrogen and sulfur in the structure, which is of course patently wrong. It also seems somewhat incomplete to compare Proteins to Carbohydrates without also comparing them to other bio-macromolecules such as lipids and nucleic acids. Is anyone adamantly opposed to removal or replacement of this line?

Banks 22:01, 24 Sep 2004 (UTC)

I agree that this is a junky sentence. I would be happy to see it go. Josh Cherry 22:06, 25 Sep 2004 (UTC)

The Protein Data bank has its own entry, and the small amount of infomation given about in this entry doesn't really add anything, mabye the PDB should be added as a see also --nixie 06:00, 8 Oct 2004 (UTC)

I demoted the section to be under Structure, and added a main article link. I think it's worth a small subsection within the larger article, but as you point out, it doesn't really need to be a top-level section. --Lexor|Talk 06:48, Oct 8, 2004 (UTC)