We all have read about low carbohydrate, high protein, low cholesterol, and low fat diets and we understand the need to maintain a well-balanced diet. Or do we? To understand the role of carbohydrates, fats, and proteins as they pertain to the functions of a body cell and how these molecules are metabolized and used in the body, we must first understand how they are molecularly structured. Let’s discuss the molecular structures of carbohydrates, lipids, and proteins.