Proteins and carbohydrates are alike in that they are crucial for the health and proper functioning of the body. They are different in that carbohydrates are made of sugars and starches, whereas proteins are made from amino acids.
Proteins are necessary for the growth and development of bodily tissues, whereas carbohydrates are the body's main source of energy. Both compounds include carbon, hydrogen and oxygen in their composition. Proteins, which are made of large molecules, also have nitrogen, phosphorus and sulfur.
Carbohydrates help regulate fat and protein in the body, as carbohydrates are needed to break down fats in the liver. Carbohydrates that are simple sugars are easy to digest; double-sugar carbohydrates, such as sucrose, require more energy to digest. Starches are the most difficult carbohydrates to digest and require the action of enzymes. Cellulose, which is another form of carbohydrate, is indigestible by humans but provides much needed bulk in the form of fiber. In the end, all digestible carbohydrates are reduced to a simple sugar known as glucose, or blood sugar.
Protein helps to build muscles, hair, skin, nails, blood and internal organs. It's also needed to create hormones, and it helps to regulate the body's water balance and pH. During digestion, the large protein molecules are broken down into amino acids.