Question

Glutamine and glutamate can form how many H bonds and why?

Answer 1

The H- bond between two atoms A and B may be indcated as above .The dotted lines denote the H-bond

The H atom is attached to atom A by pure covalent bond and to the atom B by electrostatic attraction.

The conditions for the H atom to act as a bridge between the two atoms

i) Both atoms A and B must be strongly elecronegative

ii) The atom B must have atleast one lone pair of electrons

In H-bond , the H atom acts as a bridge between two strongly electrostatic elements, holding one by pure covalent bond and the other by electrostatic attraction.

The elements which satisfy these condiions are only F, O and N

( F is the most electronegative element and it has 3 lone pair of electrons in its compounds

O is the second most electronegative element and it has 2 lone pair of electrons in its compounds

N is the next most electronegative element and it has 1 lone pair of electrons in its compounds)

Hence H- bonding is found only in the compounds of F,O and N

Structure of Glutamine

H- Bonding in Glutamine

Using the two doubly bonded oxygen atoms, Glutamine can form two H-bonds ( O = atom B)

The H atom of the OH group can be involved in the formation of a H-bond ( O = atom A)

Similarly the H atoms of the two NH₂ groups can form two H-bonds (N = atom A)

All these H- bonds are intermolecular H-bonds (H-bond between different molecules)

In addition,,there may be intramolecular (within the same molecule) H-bond between the OH group and the neighbouring NH₂ group

Structure of Glutamate

H- Bonding in Glutamate

Using the two doubly bonded oxygen atoms, Glutamate can form two H-bonds ( O = atom B)

The H atom of the OH group COOH can be involved in the formation of a H-bond ( O= atom A)

Similarly the H atom of the NH₂ group can form a H-bond (N = atom A)

The O ^- of the carboxylate ion COO^- will be involved in another H-bond (O = B)

All these H- bonds are intermolecular H-bonds (H-bond between different molecules)

In addition,,there may be intramolecular(within the same molecule) H-bond between the O^- of the COO^- group and the neighbouring NH₂ group