Talk:Lipid

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Contents 1 Lipids are fatty acid esters... and cholesterol as lipid 2 unpolar 3 Amphipathic? This makes no sense 4 Lipids are in the news this week, 5 Question? 6 Alpihatic, non-aromatic? 7 Clean-up? 8 Reasons for GA Delisting

[edit] Lipids are fatty acid esters... and cholesterol as lipid

Most of what I have seen counts cholesterol lipids, and this page in fact does so when it lists the hydrophobic and hydrophilic groups, but cholesterol is definitely not a fatty acid ester.

Jedi Dan, Cholesterol molecules are not lipids. They are actually a series of circular hydrocarbon molecules, each bonded together. I cant remember exactly what cholesterol looks like, but cholesterol and the steroid hormones derived from it typically have hydroxyl (OH), ketone/aldehyde (C=O) and methyl groups on them.

What he said is correct, assuming R1' to be a hydrocarbon chain (except the last carbon atom) and R2' to be a glycerol molecule, you could show it to be R1'-CO-O-R2' where the CO is a double bond. Check out the links below, they would probably explain better than I can in text.

Read more about steroid hormones/cholesterol at http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Cholesterol.html

Read more about triglycerides at http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/F/Fats.html

• I too have generally thought cholesterol and steroids as not being "lipids". However, the following passage appears in General Chemistry Online!: "lipid. A diverse group of organic molecules that contain long hydrocarbon chains or rings and are hydrophobic. Examples are fats, oils, waxes, and steroids." Likewise the Drug Discovery & Development Glossary states that a lipid is "an oil-soluble molecule such as a fatty acid or steroid." If on the other hand one looks at the IUPAC Nomenclature Recommendations, lipids and steroids are classed differently. Under IUPAC Nomenclature, lipids are a class of molecules that includes fatty acids, neutral fats, long-chain alcohols, long-chain bases, phospholipids, glycolipids and neuraminic acid. Therefore, I'd say that "lipids include steroids when the term (lipid) is used in a colloquial sense; however, from an organic chemistry nomenclature point of view, steroids are formally excluded from the lipid-class of molecules." Courtland 01:52, 2005 Mar 8 (UTC)
• Here's a more concise view which is part of the IUPAC Glossary of Class Names, the Lipid entry, which goes into specifics of what is included in the class: http://www.chem.qmul.ac.uk/iupac/class/lipid.html. Now this page says that the term lipid is "a loosely defined term for substances of biological origin that are soluble in nonpolar solvents. They consist of saponifiable lipids, such as glycerides (fats and oils) and phospholipids, as well as nonsaponifiable lipids, principally steroids." Therefore, steroids are lipids afterall and their separation in the IUPAC nomenclature does not indicate they are unrelated. Courtland 02:03, 2005 Mar 8 (UTC)

Sometimes categories can be incompletely congruent in different contexts. For example, cholesterol is always considered a lipid in a medical context, and this would be a common reason for a reader to look at this article. We need a section on cholesterol and other sterols explaining how they differ from triglycerides and in what contexts they are or are not considered lipids. alteripse 14:07, 24 December 2005 (UTC)

Cholesterol is a lipid... in all contexts. The problem is that the term lipid refers to a huge variety of hydrophobic biomolecules, which is why things as dissimilar as fatty acids and sterols are classified as lipids. GFP 06:09, 16 June 2006 (UTC)

[edit] unpolar

I have never seen this before - should be non-polar (or nonpolar)? --Anon

Thanks for catching that. --maveric149

[edit] Amphipathic? This makes no sense

You mean Amphiphilic right? I hope you dont mind if I make a few minor chances to make it more technically accurate. Jedi Dan

Amphipathic and amphiphilic are both correct and both mean that the molecule is part hydrophobic and part hydrophilic. GFP 06:15, 16 June 2006 (UTC)

Some people introduce a difference between amphipathic and amphiphilic :

• amphipathic refers to molecule that are preferentially located at a polar-apolar interface. From this point of view, a phospholipid is amphipathic.
• amphiphilic refers to compounds that can be solved in a polar or an apolar phase, but are not necessarely located at the interface.

-- hope it's help 136.159.234.84 20:42, 12 July 2006 (UTC)

[edit] Lipids are in the news this week,

and I thought this page should update to reflect... but don't have the time to do it now.

A quote

In the LIPID MAPS classification scheme, lipids are divided into eight primary categories: fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterol lipids, prenol lipids, saccharolipids, and polyketides. These categories are based on the functional backbone of the lipid molecule from a chemical standpoint. The categories are further subdivided into classes and subclasses to handle the existing and emerging arrays of lipid structures.

Source: [1]

I'll check back later, but perhaps someone with more biology than I can start to take a whack at that. JRice 21:28, 13 May 2005 (UTC)

Great idea. GFP 06:28, 16 June 2006 (UTC)

[edit] Question?

what is the primary physiological function of lipids: a. provide absorbtion of fat soluble vitamins b. conserve heat c. provide material for synthesis of hormones d. supply energy ???

How about e. all of the above? alteripse 03:37, 10 January 2006 (UTC)

[edit] Alpihatic, non-aromatic?

I am a chemistry novice and am a bit confused by this article. The intro says that "Lipids are one class of aliphatic hydrocarbon-containing organic compounds,"

and in the 'Structure' section we have:

"Some lipids are linear aliphatic molecules, while others have ring structures. Some are aromatic, while others are not."

Okay so far, perhaps, but in the 'Aliphatic compounds' article we have:

"In chemistry, aliphatic compounds are non-aromatic organic compounds"

There appears to be a contradiction here which somebody could maybe resolve.

Well, this all got quite mixed up. Aliphatic means not aromatic. Lipids are generally aliphatics, and the most popular (fatty acids, glycerides, etc.) are entirely aliphatic. But lipids can also have aromatic groups attached, for instance resorcilonic lipids, and they are then called alicyclic. Karol 12:46, 4 April 2006 (UTC)

Makes much more sense. Thanks for the edit, Karol. User:Kaplin 09:17, 5 April 2006 (UTC)

The thing that makes it hard to define a lipid is that it can have just about any structure, so long as it is a predominantly hydrophobic, hydrocarbon-based molecule. This should be clearer with the latest edits. GFP 06:25, 16 June 2006 (UTC)

[edit] Clean-up?

Does anyone know why the CleanUp tag is on this article? There's no discussion here on the Talk page as to why the tag is there, so it's hard to understand when it would be appropriate to remove it. If no one points out why the tag is there after a few days, and as long as nobody disagrees, I'm going to remove it. Cheerio! Mineralogy 08:24, 21 April 2006 (UTC)

Well, at the time I put the tag up, this page was more or less chaos. Now things are better, although still under my expectations. I myself haven't found the time to imprive this. I guess it would be Ok to take it down now. Karol 11:04, 22 April 2006 (UTC)

01:02, 9 May 2006 (UTC) I concur with "more or less chaos."

• In the "Types of Fats" section, "eiconasoids" are listed next to unsaturated as though it is another name for unsaturated fatty acids. That's not even a little bit true. Could be a subheading under unsaturated, but even that is dubious.
• This sentence is misleading:
  "In nature, almost all double bonds in fatty acids are found in the cis configuration." You could say "the majority." Or you could explain that most fatty acids have at least one cis bond. However, trans bonds in fatty acids are quite common. Most linoleic acid is a hybrid of one cis, one trans bond.
• Jedi Dan "fixed" amphipathic to say amphiphilic, but most biochemistry texts use amphipathic in that context; it should be changed back. It is linked; people can look it up if they are unclear.
• There is a subheading "fatty acids" followed by "other", but "other" includes sentences which are explicity about fatty acids.
• The section on Public Health is not very well written and is better covered and maintained elsewhere.
• In general, the prose is uneven.

EEsterling

I just performed extensive cleanup and restructuring. I also corrected a lot of factual errors that had crept in since I last checked out this page and added some information. GFP 05:48, 16 June 2006 (UTC)

man that's a ghetto-looking picture compared to the other organic groups. ays 04:34, 27 September 2006 (UTC)

[edit] Reasons for GA Delisting

This article's GA status has been revoked because it fails criterion 2. b. of 'What is a Good Article?', which states;

(b) the citation of its sources using inline citations is required (this criterion is disputed by editors on Physics and Mathematics pages who have proposed a subject-specific guideline on citation, as well as some other editors — see talk page).

LuciferMorgan 01:04, 9 November 2006 (UTC)