Proteins and Polypeptides – Basics, Structures, Functions, and Properties
Each protein contains one or more polypeptide chain. The chemical properties and order of the amino acids determines the structure and function of the polypeptide.

Protein: What It Is, Types, Uses, Needs, Deficiency
Proteins are large molecules made up of chains of amino acids that are important for cell function, tissue structure, and body regulation. Most people in the U.S. consume more protein than needed, with dietary guidelines suggesting about 6.5 ounces per day for men and about 5 ounces for women.

Protein - Wikipedia
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues.

What Are Proteins? Definition, Types & Examples
People generally say “protein” (or “dietary protein”) when talking about nutrition and “proteins” when discussing the science of how the individual molecules work within your body.

Protein • The Nutrition Source
Protein is an essential macronutrient, but not all food sources of protein are created equal, and you may not need as much as you think. Learn the basics about protein and shaping your diet with healthy protein foods.

Protein | Definition, Structure, & Classification | Britannica
A protein is a naturally occurring, extremely complex substance that consists of amino acid residues joined by peptide bonds. Proteins are present in all living organisms and include many essential biological compounds such as enzymes, hormones, and antibodies.

Protein: Why Your Body Needs It - WebMD
Your body needs protein to stay healthy and work the way it should. More than 10,000 types are found in everything from your organs to your muscles and tissues to your bones, skin, and hair.

What are proteins and what do they do?: MedlinePlus Genetics
There are 20 different types of amino acids that can be combined to make a protein. The sequence of amino acids determines each protein’s unique 3-dimensional structure and its specific function.

What is protein? High protein foods, explained by nutritionists
What is protein? Protein is one of the body’s three macronutrients, along with carbohydrates and fat. Each provides calories and energy, but they serve different purposes.

Proteins | Nutrition.gov
Find how much protein to eat per day, what foods are high in protein, and why protein is important.