Unbelievable: Sugar Molecules More Complex than DNA!

[Mentat]

I've just recently read an article, about sugar molecules that form inside of cells, that was really shocking. Apparently, current research has discovered that some of these sugar molecules are many time more complex than DNA!

What do you guys know about this? What is the purpose of these unfathomably complex molecules?

 

[Monique]

[?] dna is not complex at all, it's very predictable.. a sugarphosphate backbone with different bases attached twisted into a helix..

And for the sugar molecules being complex.. not that shocking either? It is true though, the building of such a complex sugar molecule has to be done step by step and requires many different enzymes (this all takes place mainly in the golgi aparatus).

The function could be several: for one you have the mannose-6-phosphate moiety, which targets molecules to the lysosome. Another function could be protection against the environment. You will mainly find a sugar coating (glycocalix) on the 'outside' of cells (which also includes the inside of organelles, which physiologically resemble 'outside'). For instance, the internal membrane of the lysosome is coated mainly with N-glycosilated sialic acid. Why? Because the sialidase enzyme is very inefficient, and thus protects the digestive organelle from digesting itself. Sugars could also be involved in cell recognition and adherence. The list is long :P

 

[Mike H]

Carbohydrate chemistry is remarkably diverse - there are all sorts of isomers, linkages, and modifications that exist for carbohydrates.

For example, for six-carbon sugars, one can have anomeric forms on top of the standard D/L isomers, and then you can have five or six membered cyclic forms (furanoses and pyranoses). Once you start creating n-saccharides, you can have linear polysaccharides, branched-chain saccharides, with varying glycosidic bonds (alpha or beta). Once you start adding chemical modifications and such, things can get very messy in no time at all.

One of the interesting roles postulated for sugars in cells is actually in protein stability, especially when it comes to biochemical studies. Apparently high concentrations of sugars can help stabilize proteins by providing hydrogen bond donors/acceptors to proteins.

 

[Mentat]

Thanks for the input, guys. One question, though not really related to the subject of the thread: You said...

Originally posted by Monique
[?] dna is not complex at all, it's very predictable.. a sugarphosphate backbone with different bases attached twisted into a helix..

And this seems logical to me, but what about the huges possibility for variation and that kind of thing? These seem like complex functions for such a simple structure.

Also, what is "junk DNA"...I've recently heard about it, and didn't know what to make of it.

 

[iansmith]

Originally posted by Mentat
Also, what is "junk DNA"...I've recently heard about it, and didn't know what to make of it.

It is DNA that does not have a function.

 

[Monique]

Actually 'junk DNA' is an outdated term, it was used for all the kb of non-coding bases in between of genes. But it turn out that such DNA still has a function (although largely unknown), for instance on histone packing. Junk DNA can also contain transposons or pseudogenes, I believe.