Question about hydrogen bonding in secondary structures?

[forchina]

Hi guys,
my teacher said that there is hydrogen bonding between the R groups of alpha-helices and beta pleated sheets. However, I looked this up on the internet but it doesn't say anything about it. Instead it says there is hydrogen bonding between the NH and CO group of amino acids in the secondary structure? So now I'm confused is it between the R groups as well?
Thanks

[katerina]

I think they're called intra-peptide hydrogen bonds.

However, don't stress too much, you won't be asked that in an exam. You'll be asked to describe the structure though (mentioning the beta sheets and helixes often does the trick).

Goodluck with the rest of your studies.

[Stick]

It *could* be between the variable functional groups between amino acids, but depending on what's there, you can't just assume there will be hydrogen bonds every single time.

[kenhung123]

It definitely can, if you look up the 20 amino acids, you will be able to identify certain functional groups that have hydrogen bonding capacity as identified in any other hydrogen bonding substance.

[forchina]

But are they generally found between the NH and CO group?

Thanks guys for all your answers. 

[thushan]

There is hydrogen bonding between NH and CO groups - this hydrogen bonding alone is responsible for secondary structure.

There is also hydrogen bonding between R groups (amongst ionic, covalent etc); together, these are responsible for tertiary structure.

[Yacoubb]

Simply knowing how to describe the structure of each secondary structure would be adequate:

Alpha Helices:
A tightly coiled chain of amino acids that forms a spiral conformation; every amino acid is joined to the fourth amino acid earlier residue by a weak hydrogen bond.

Beta-pleated Sheet:
The amino acids chains fold so that the R-variable groups of one amino acid chain are parallel with the R-variable groups of the other amino acid chain, and so hydrogen bonds form.

Referring to the hydrogen bonds existing between the Carboxyl (COOH) group and the Amino group (H₂N); this is an intra-peptide bond and is not examinable in a VCAA exam.. its more or less the Chemistry exam aspect of Organic molecules.

[Yacoubb]

There is also hydrogen bonding between R groups (amongst ionic, covalent etc); together, these are responsible for tertiary structure.

Just adding to that, the overall three-dimensional shape of a protein is determined by the irregular foldings of amino acid chains (secondary structures) and the formation of bonds - these bonds are:
* Ionic bonds - between the positively charged and negatively charged R-variable groups.
* Hydrogen bonds - (see secondary structure for alpha helices/ beta-pleated sheet).
* Disulfide bridges - the formation of disulfide bridges joining cysteine amino acids together.
As mentioned this forms the tertiary structure of the protein, critical to its function, especially when we look at enzymes and how the active site of an enzyme complementary to a substrate depends on its tertiary structure.