how-does-histidines-r-group-structure-allow-it-to-accept-a-hydrogen-ion

Question

How does histidine's R group structure allow it to accept a hydrogen ion?

Accepted Answer

It contains a 5-membered ring with nitrogen atoms.

Answer

It contains a hydroxyl group that accepts hydrogen ions.

Answer

It has a carboxyl group that donates hydrogen ions.

Answer

It has a long carbon chain with an amino group.