Acid means that the hydrogen has a tendency to separate becoming plus charged while leaving a minus charge on the oxygen. There are 20 amino acids. They each have a different R group. Secondary Structure - is the interaction between segments which are near each other. Primary structure - is the sequence of subunits in the chain.
Secondary structure includes hydrogen bonds.
These bonds are very weak individually, but they tend to be numerous. A hydrogen bond means that a hydrogen atom attached to one group is drawn to a negative charge on another group near it.