Protein, an essential nutrient for the human body, is the second most abundant component of the body after water. Comprising about 16% of our bodyweight, proteins play several critical roles. They help to repair and build our tissues, and are the component of muscles which provide a structural framework to the body. They help in metabolism by acting as enzymes, hormones, or carriers. Keratin protein in the hair, nails, skin, (as well as feathers and hooves in birds and animals) act as a protective barrier. Protein maintains pH and fluid balance in the body. They are also a source of energy. Each gram of protein provides 4 Kcal of energy. In the form of antibodies, proteins play an important role in immunological responses. They also act as a lubricant in internal cavities.