What are proteins?

Proteins are defined as polymers of amino acids, which means they are large molecules made up of long chains of amino acids linked together by peptide bonds. Each protein is composed of one or more polypeptide chains that fold into a specific three-dimensional shape, allowing them to perform a wide variety of functions in living organisms. These functions can include acting as enzymes, providing structural support, facilitating communication between cells, and transporting molecules. The sequence of amino acids in a protein determines its unique structure and function, making the understanding of proteins crucial in biology and medicine.

The other options do not accurately describe proteins: complex carbohydrates consist of long chains of sugar molecules, simple lipids are fats that do not form proteins, and nucleic acids are polymers like DNA and RNA that serve different roles in genetic information storage and transfer. Thus, identifying proteins as polymers of amino acids is fundamental to understanding their biological significance.