Starches are to simple sugars as proteins are

to amino acids. As starch breaks down in the presence of many digestive enzymes to glucose, the simplest form of all complex sugars, proteins too break down into its simpler constituents.

Answer: Amino acids.

Explanation: Proteins break down into its Amino acids. Amino acids are building blocks for protein.

Amino acids are organic compounds that link up to form proteins. Proteins are the building blocks of life. Amino acids are left when proteins is broken down or digested.