The food you eat provides your body with macronutrients -- the nutrients your body needs in large amounts to support normal growth and metabolism. The types of macronutrients include carbohydrates, proteins and fats. Although carbohydrates and proteins both provide the body with calories used as energy, they also differ in many ways.
Molecules
Carbohydrates consist of sugars molecules made up of carbon, hydrogen and oxygen. Foods classified as simple carbohydrates contain sugars such as fructose -- fruit sugar, sucrose -- table sugar, dextrose or glucose. Carbohydrates containing complex sugar molecules that consist of three or more sugars linked together are classified as complex carbohydrates.
Proteins consist of amino acids, commonly known as the building blocks of proteins. Twenty different amino acids important for humans combine together in various combinations to form proteins. Amino acids all contain a carbon atom bound to a hydrogen atom, an amino group that contains a nitrogen atom and a carboxyl group containing carbon with oxygen.
Use in Body
Carbohydrates and proteins perform the same basic function -- to provide the body with energy. The way the body uses each type of macronutrient to support bodily functions differs. During digestion, the body breaks down carbohydrates into small glucose molecules. The glucose molecules then enter the bloodstream to travel to cells. With the aid of insulin -- a hormone produced by the pancreas, cells uptake the glucose and use it for energy. Cells within the liver convert excess glucose into glycogen -- the storage form of glucose -- which the body can use for energy later.
After consuming proteins, the digestive tract then breaks them down into their individual amino acids. The body can then use these amino acids to build the thousands of proteins needed throughout the body. Because humans can only produce 11 of the 20 amino acids the body needs, it must get the other nine amino acids, known as the essential amino acids, from foods. It is therefore important to consume a variety of protein sources to get all the necessary amino acids.
Sources
Several different types of foods provide carbohydrates. The main types of carbohydrates include sugars, starches and fiber. Fruits contain sugars and fiber and serve as good sources of carbohydrates. Grains, especially whole grains used in breads, pastas and cereals, that contain the germ, bran and endosperm, contain both starch and fiber and therefore provide carbohydrates to use for energy. Some vegetables contain starch, including corn, peas and potatoes, therefore providing carbohydrates.
Because animal products contain complete proteins -- meaning proteins that provide all the essential amino acids, they serve as the best source of protein. Animal foods include meat, poultry, fish, eggs and dairy products. Soybeans are the only plant-based food that provides complete proteins. Soybeans produce soy foods, such as tofu and milk, that serve as a good source of protein. Some vegetables that contain incomplete proteins and contribute to protein intake include beans, nuts and whole grains.
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