The structural unit of proteins is an amino acid. Similar to carbohydrates, protein molecules are compromised of carbon, hydrogen, and oxygen. The only difference is that protein also contains nitrogen. There are four different types of protein:
Myosin-fibrous protein found in muscle.
Collagen-structural protein, strengthens bone, cartilage, and skin to maintain body form.
Hemoglobin-forms protective pockets around iron, allowing for transport in the bloodstream.
Albumin-the most abundant plasma protein, albumin serves as a carrier protein for drugs, enzymes, hormones, and trace elements.
Similar to carbohydrates, not all proteins are the same. Notice that animal proteins rank the highest in chemical score and biological value.
If the discussion for carbohydrates is what and when, for protein it is whether the protein is complete or incomplete.
There are 9 essential acids that are body cannot synthesize and needs to get from food. These are essential amino acids and are: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, and Valine.
A complete protein contains all of these, while an incomplete protein may contain some, but not all. In most cases, animal proteins are always complete proteins. If it has eyes, it most likely has all essential amino acids. If eating vegetarian proteins, trying pairing proteins to complement each other, such as beans and rice.