Which of the following fights against infectious pathogens?

Identify the structure of the amino acid shown in the image.

Which conjugated protein is synthesized by copper?

What is the macromolecular polymer formed by amino acids called?

The three-dimensional arrangement of a polypeptide chain forms which protein structure?

$A$: Hemoglobin is a molecule formed by interactions between four heme groups.
$R$: Hemoglobin is a quaternary protein.