The Book of Protein Prologue: Protein is one of three macronutrients necessary for the body’s growth, development and maintenance. Chapter 1: What are Proteins? Proteins are large molecules composed of amino acids. They are the body’s major source of nitrogen. Chapter 2: The Importance of Protein We need protein for: cell growth, repair, and continuous maintenance hormone functions enzymatic reactions fluid, electrolyte and pH balance energy source Chapter 3: A Day in the L