The Role of Nutrition in our Health Practice Test

Nitrogen is a defining element of proteins because amino acids—the building blocks of proteins—contain a nitrogen atom in their amino group. Among the macronutrients, only proteins include nitrogen in their structure, while carbohydrates and lipids are made from carbon, hydrogen, and oxygen and do not contain nitrogen. Vitamins are micronutrients, not macronutrients. So the description points to protein as the correct choice, since its amino acids inherently carry nitrogen and form the many proteins the body uses for growth, repair, and function.