Saturated/Hydrogenated fats and their digestion.

  • Thread starter wasteofo2
  • Start date
464
1
Is there a difference between saturated and hydrogenated fats, or are hydrogenated fats simply unsaturated fats which have been saturated?

How readily are saturated fats (and hydrogenated, if they're a different thing) digested/stored/used for energy? I've heard claims by supposed health experts that hydrogenated fats stay in your body practically forever, is that the case, or is it just health nuts over-exagerating?

Thanks,
Jacob
 
203
0
i'm not sure.. but apparently chemically produced saturated fats (like margarine) often contain chemical bonds that are completely unlike anything produced in nature. I think it was "trans" double bonds or something?
 
completely saturated fats contains no double bonds.

hydrogenated fats are unsaturated fats that have (through industrial chemistry) make to be completely saturated by hydrogenation.

trans fat isomers do not exist in nature, yet they are guaranteed to arise through industrial chemistry since the hydrogenation process is never 100% complete - a small percentage of the fats will oxidize back to their olefin form, and chemically (but not biologically) both cis and trans isomers will be present racimically for that small percentage of the fat.

i have been told that the trans fats cannot be degraded by the bio pathways (beta-oxidation), although i must admit that i never understood this since the trans isomers are intermediates in that pathway...the acyl-CoA oxidase makes the enoyl (trans olefin) which then gets oxidized to a keto so that the high-energy bond can be released (releasing energy) and the fatty acid broken down by 2 carbons. i would think that having a trans double already there would just make it that much easier for that pathway!

any ideas?
 
464
1
quetzalcoatl9 said:
trans fat isomers do not exist in nature, yet they are guaranteed to arise through industrial chemistry since the hydrogenation process is never 100% complete - a small percentage of the fats will oxidize back to their olefin form, and chemically (but not biologically) both cis and trans isomers will be present racimically for that small percentage of the fat.
I'm not the most well-versed guy in bio-chem, so that paragraph kinda went over my head. How are trans and cis fats different than natural fats, and what are natural fats called (is it just "fats"?)? Also, what is an olefin form? What does the word racimically mean?

Thanks alot,
Jacob
 
wasteofo2 said:
I'm not the most well-versed guy in bio-chem, so that paragraph kinda went over my head. How are trans and cis fats different than natural fats, and what are natural fats called (is it just "fats"?)? Also, what is an olefin form? What does the word racimically mean?

Thanks alot,
Jacob
well, rotation is not possible around a carbon double bond. so atoms that are bound to those carbons are locked into place, so to speak. take [tex]C_2H_2Cl_2[/tex], for example, with a double bond between the carbons. there are three possible forms (aka isomers) of that molecule:

1) one with both Cl's bound to the same carbon
2) one where each Cl is bound to a carbon, on the same side of the double side
3) one where each Cl is bound to a carbon, across from each other

2 is called the "cis" form, and 3 is called the "trans" form. it is hard to explain without pictures, so maybe you can look them up on google if that doesn't make sense. cis fats are the natural ones.

olefin is another name for an alkene (aka a double-bonded hydrocarbon).

racemic refers to the fact that typically in a chemical reaction, you will wind up with (whether you want it or not) a mixture of isomers of the same molecule. this is not true (in general) for biochemical systems, surprisingly: they almost always make or use only one isomer of something (whether it be fat, sugar, amino acid, nucleotide).

it is also an interesting (yet unrelated) fact that why biological systems use only one isomer (enantiomer to be specific) of biomolecules is completely unknown. scientific tests for life on mars have been proposed for screening the mars terrain for any abundance of one isomer of organic molecule over another - such a find would strongly suggest the presence of life.
 

Ouabache

Science Advisor
Homework Helper
1,338
7
wasteofo2 said:
I'm not the most well-versed guy in bio-chem, so that paragraph kinda went over my head. How are trans and cis fats different than natural fats, and what are natural fats called (is it just "fats"?)? Also, what is an olefin form? What does the word racimically mean?
http://www.ualberta.ca/~dgeelan/cistrans.jpg[/URL] where the attachment is diagonally opposite. (see the side chains - R, in the link given) [i]Olefin[/i] is just hydrocarbon molecule containing at least one carbon-carbon double bond)

Oils and fats fall into a category called lipids. One way of distinguishing them is, oils are liquid at room temperature while fats are solid or semisolid. (That distinction becomes a little ambiguous when room temperature happens to be cold. For instance olive oil becomes semi-solid at 9 deg C. Similarly palm and coconut oils are liquid in the warm regions they are produced, yet become semisolid in cooler climates of Northern US and Great Britain). When we define room temperature as 22 deg C (72 deg F), there is no ambiguity.

It is the [B]fatty acid[/B] in a fat that is described to have a [I]cis[/I] or [I]trans[/I] [PLAIN]http://www.mansfield.ohio-state.edu/~sabedon/047cis.gif[/URL]. (As you will see in the weblink, there are many types of fatty acid).

[B]Natural fats[/B] are simply those produced in nature.. Natural fats may contain [I]trans[/I] fatty acids (naturally occurring in beef, pork, lamb, milk, butter), and [I]cis[/I] fatty acids (found in olive, canola and sunflower oils)

[I]Racimically[/I] [sic] refers to racemic. In chemistry, it normally refers to an equal mixture of [URL]http://www.nature.com/news/2004/040726/images/nbt0804-953-F2.jpg[/URL] (molecules that can exist in both a left and right handed arrangement, also described as mirror images of one another). I believe quetzalcoatl9 was using the word in a descriptive sense, to mean a "mixture of cis and trans forms of the same fat".

Non-natural, human-made fats (synthesized or chemically altered by some process like deep-frying) tend to contain a greater amounts of [I]trans[/I] fatty acids. Consumption of this type is said to elevate risks to cancer and heart disease.
 
Last edited by a moderator:
i stand corrected, there are some naturally occuring trans fatty acids.

also, as Quabache has pointed out, i should have said "mixture of stereoisomers" instead of "racemic" because technically racemic means enantiomers.
 

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving

Hot Threads

Top