Search
Ask a question
0 1

Where are hydrogen bonds located in nucleic acids and carbohydrates?

I'm having trouble answering the following questions: “where would you find hydrogen bonds in nucleic acids?” “where would you find hydrogen bonds in carbohydrates”?
Tutors, please sign in to answer this question.

2 Answers

Gabriel: A key here is that hydrogen bonds are relatively weak interactions BETWEEN molecules. So a COVALENT bond between an oxygen and hydrogen in one water molecule, for example, is NOT a hydrogen bond.
 
The origin of hydrogen bonding is the unequal 'sharing' of electrons between a hydrogen (with a weak 'pull' on electrons, more formally a relatively low electronegativity) and generally an oxygen or nitrogen that the H is covalently bonded TO. Another way of looking at it is:
H--->O<---H, where the arrowheads indicate the Oxygen is 'winning' the tug-of-electrons.
 
This leaves the HYDROGEN somewhat positive overall (because it's 'lost' its fair share of electrons) and the oxygen correspondingly negative.
 
A hydrogen bond is the interaction that results between the somewhat-postive H from ONE molecule and the somewhat-negative O or N on ANOTHER.
 
Note that carbon also has a relatively weak electron pull, so oxygens & nitrogens that are covalently bonded to carbons are also somewhat negative in charge and can participate in H-bonds on other molecules.
 
If you look at HOW two bases in DNA or RNA are interacting, you should be able to see the H-bonds! (H-bonds are often shown as dashed lines to indicate they are different & weaker than covalent bonds)

Comments

Not sure I've ever heard of hydrogen bonds forming when O and N are bonded to C.  I'm pretty sure they only occur when H is bonded to O, N or F.
I think we've crossed wires on who "has" the H and to whom the H is bonded/shared. I'm referring to the electronegative atom to which hydrogen is weakly bonded:
 
In GC basepair, for example, two instances of
 
-NH2 ---- O=C<
(Dashed line is H-bond)
so an H is covalently bonded to N, but the hydogen bond is between that H and an oxygen which has partial negative charge by virtue of "stealing time" with electrons shared with carbon to which it is covalently bonded (the 'less than' sign indicates bonds between carbon and other members of purine ring)
Thanks for clarifying. We are on the sa page. 
Hydrogen bonds occu when a H atom is bonded to a N, O or F atom. So in nucleic acids hydrogen bonding occurs between adenosine and thymine bases and between cytosine and guanine bases.  In carbohydrates,hydrogen bonding occurs between the -OH groups on the molecules.