Out of the following,which is the best category to describe proteins?

Enzymes belong to which class of compounds?

In aqueous solution,amino acids exist as.......

How many subunits are present in hemoglobin?

$A$ nanopeptide contains $\dots$ peptide linkages.

Explain the terms primary and secondary structure of proteins. What is the difference between $\alpha$-helix and $\beta$-pleated sheet structure of proteins?