Answer the following question given this paragraph: 

Amino acids are the "building blocks" of proteins. There are 20 different common amino acids. The structural formula of the simplest amino acid, called glycine, is shown in Figure below . Other amino acids have a similar structure. The sequence of amino acids and the number of amino acid chains in a protein determine the protein’s shape. The shape of a protein, in turn, determines its function. Shapes may be very complex. You can learn more about the structure of proteins at the URL below.


Q: What are the "building blocks" of proteins?

 Choices:

- hormones

- enzymes

- nucleic acids

- amino acids

A:
amino acids
