Mini Lesson: Protein

Video Transcript

Protein Structure

Proteins are a macronutrient, meaning our body needs quite a bit of it compared to the necessary amount of vitamins and minerals. The proteins that we eat or find in the body are quite complex, but they are all made of different combinations of amino acids. Each amino acid has a similar base structure made of carbon, hydrogen, oxygen, and nitrogen, but each amino acid has a unique addition to that base structure that will affect the role that it plays in the protein structure. 

Amino acids that are joined together by peptide bonds are referred to as peptides. Protein structures can be as simple as a few amino acids making di- or tripeptides, but they are more often long polypeptide chains that have been coiled or twisted and joined with other polypeptides to create various complex protein structures than can include hundreds of amino acids, or more.

Digestion of Protein

The complexity of proteins requires multiple steps to completely break apart the amino acids needed by the body. Chemical digestion of proteins starts with the stomach acid that works to break apart the twisted and coiled structures, leaving long polypeptide chains. Special enzymes in the stomach begin breaking apart these long chains, but more enzymes from the pancreas and the cells of the small intestine are necessary to break these proteins into the amino acids and small peptides that can be absorbed into the body.

Absorption of Protein

The cells of the small intestine have specialized molecules in the cell wall that will either grab onto individual amino acids, or small peptides. Once the di- or tripeptides are brought into the cell, the peptide bonds are broken within the cell, which should leave only individuals amino acids that are passed to the blood vessels that will take them to the liver.

Function of Protein in the Body

Amino acids are used to form many different structures in the body. Though we are most familiar with their use for building muscles, amino acids are necessary to form proteins for all cells and are important in the formation of healthy bone and connective tissue as well. Beyond their important roles in forming body structures, proteins also help to transport nutrients in the blood, form signaling molecules that help the cells communicate with each other, create antibodies that help the immune system identify and eliminate threats to the body, and form the numerous enzymes that not only support healthy digestion, but perform countless processes that are necessary to keep us alive! One particularly important point about proteins is that our body uses specific peptides to identify whether or not a food or an organisms is a threat to our body.

Food Sources of Protein

Amino acids are found most significantly in foods from animals, legumes, nuts, seeds, and to a lesser extent vegetables.  We need to make sure that we have enough of all the different types of amino acids so that our bodies will have the appropriate building blocks it needs to create all the enzymes, hormones, antibodies, and all the other structures that rely on proteins. Although our bodies are able to use some amino acids to make other types of amino acids, there are nine amino acids that are considered essential because our bodies are not able to make them, which means we have to get them from the foods that we eat. There are also times when our body cannot keep up with making certain amino acids, so they are considered conditionally essential and must also come from food.

Animal-based proteins such as meat, poultry, seafood, eggs, and many dairy products can provide all the essential and conditionally essential amino acids that our bodies need. However, plant-based protein foods like legumes, nuts, and seeds can be a great way to meet the bodies needs. Just remember it is very important to make sure we are getting the proper combination that has all the essential and conditionally essential amino acids that our bodies require.

Why Proper Digestion of Protein is Important

Though amino acids can technically be used for energy production, this macronutrient is most important for its structural and functional roles in the body. The complexity of protein structure in our food require optimal digestive function to ensure that we can properly take in the amino acids that we need. Unfortunately, poor digestive function can allow undigested proteins to enter the body and trigger the immune system, leading to various food reactions and even the development of autoimmune disease.