Here's why:

* Proteins are complex molecules made up of amino acids linked together in long chains. They have a wide variety of functions, including:

* Structural support: Proteins like collagen and keratin provide strength and shape to tissues, organs, and the body as a whole.

* Enzymes: Proteins that catalyze (speed up) chemical reactions in the body.

* Hormones: Proteins that act as chemical messengers.

* Antibodies: Proteins that help fight off infection.

* Transport: Proteins like hemoglobin carry oxygen in the blood.

While other building blocks are important, proteins play the most fundamental role in the structure and function of living organisms.