From Shereen Jegtvig,
Your Guide to Nutrition.
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Proteins are necessary for building the structural components of the human body, such as muscles and organs. You also need proteins to keep your immune system healthy, synthesize neurotransmitters, create and signal hormones, and much more. A balanced diet supplies you will all of the protein you need. Meats, eggs, and dairy products are significant sources of protein, but you can also get protein from a variety of grains, legumes, nuts, and seeds.

Just a Tiny Bit of Protein Chemistry

Proteins tend to be large molecules made up of several building blocks called amino acids. The general structure of any amino acid molecule includes a carboxyl group of atoms, an amine group and a side chain. The carboxyl group contains one carbon, two oxygen, and one hydrogen atom. The amine group contains one nitrogen atom with two hydrogen atoms attached to it.

All 20 amino acids have different side chains, which vary in shape including straight chains of atoms, branched chains of atoms and rings of atoms. The side chains may include carbon, hydrogen, sulfur, nitrogen and oxygen atoms. The configuration and molecules found in the side chain is what differentiates one amino acid from another. The branched-chain amino acids are isoleucine, leucine, and valine. These amino acids are necessary for muscle structure. Tyrosine, phenylalanine and tryptophan are called aromatic amino acids. Each one contains a side chain with a ring-shaped formation. These three amino acids are needed for neurotransmitter production.

There are 20 different amino acids. Amino acids are linked together to form peptides, which are small chains of amino acids. The peptides are then linked together to form larger proteins.

There are thousands of different proteins that carry out a large number of jobs in the human body. Even though so many different proteins are at work in your body, you don't have to worry about consuming each individual protein from the foods you eat. Your body will make those proteins. All you need to do is to make sure your body has a healthy supply of all 20 of the different amino acid "building blocks." Having enough of those amino acids is easy because your body can make 11 of them from other compounds already in your body. That leaves eight amino acids that you must get from your diet. Those eight amino acids are called "essential amino acids."

Non Essential and Essential Amino Acids

The 11 non-essential amino acids are not called "non-essential" because they are not important. They are important and your body requires them to perform several functions. These amino acids are called "non-essential" because you don't need to get them from your diet. Your body can build those 11 amino acids from chemicals already present in your body. The non-essential amino acids include:

• Alanine
• Arginine
• Asparagine
• Aspartic Acid
• Cysteine
• Glutamic Acid
• Glutamine
• Glycine
• Proline
• Serine
• Tyrosine

The amino acids arginine, cysteine, glycine, and tyrosine are sometimes also considered to be "conditionally essential." That means most people manufacture them on their own, but some with certain illness or genetic abnormalities don't and need to get them through their diets.

The nine essential amino acids are called "essential" because you can't manufacture them, you have to eat proteins that contain those amino acids. Those essential amino acids include:

• Histidine
• Isoleucine
• Leucine
• Lysine
• Methionine
• Phenylalanine
• Threonine
• Tryptophan
• Valine

Do you really need to worry about essential amino acids when you plan your daily meals?

Not really. Animal sources of protein such as meat, eggs, and dairy products are "complete proteins." That means that each protein found in an animal product contains each of the nine essential amino acids. Vegetarians and vegans may need to pay a little more attention to the dietary proteins. Plant proteins are called "incomplete proteins." Each plant protein is missing at least one of the nine essential amino acids. However, every amino acid is found in some type of plant, so you can combine different plant proteins to get all of the amino acids you need. We will get back to this later in the lesson.

Protein Functions in the Body

There are many different proteins in your body, and they perform different functions. Proteins functions include:

• Contributing to enzyme activity that promotes chemical reactions in the body
• Signaling cells what to do and when to do it
• Transporting substances around the body
• Keeping fluids and pH balanced in the body
• Serving as building blocks for hormone production
• Helping blood clot
• Promoting antibody activity that controls immune and allergy functions
• Serving as structural components that give our body parts their shapes