Polymerisation: compare question

Ethene, $\ce{CH2=CH2}$, polymerises to form poly(ethene). Amino acids, $\ce{H2N-CHR-COOH}$, polymerise to form polypeptides.

Compare the type of polymerisation reaction that produces poly(ethene) with the type that produces a polypeptide. In your answer, refer to:

• the functional groups and bonding in the monomers
• the mechanism of the polymerisation
• the by-product(s), if any, of each reaction
• the structure of the polymer chain formed.