Proteinogenic amino acid

Tiny bits build your body.

These bits are called amino acids. They work together to make proteins. There are 22 kinds of these bits in life.

Some kinds are very special. Your body can make 12 of them. But you must eat the other nine. These are called essential amino acids. You get them from your food. Eating good food helps your body stay strong!

Tiny building blocks make up the proteins in all living things. These blocks are called amino acids.

Some amino acids are used to make proteins. We call these proteinogenic amino acids. The name means "protein creating."

There are 22 proteinogenic amino acids in all known life. Most living things use 20 standard kinds. Two others, called selenocysteine and pyrrolysine, use special ways to join proteins.

Other amino acids do not help make proteins. These are called non-proteinogenic amino acids.

Humans can make 12 of the proteinogenic amino acids. Our bodies build these from other small molecules. We cannot make the other nine. These are called essential amino acids. You must get them from the food you eat. Nine essential amino acids include histidine and leucine. They also include lysine and valine. Other ones are isoleucine, methionine, phenylalanine, threonine, and tryptophan.

Proteinogenic amino acids are the special building blocks used to build proteins. The word "proteinogenic" means "protein creating." While there are many different types of amino acids, only a small group is used by living things to make proteins. These amino acids are added during a process called translation. This is when a cell reads instructions from RNA to build a protein chain.

How does this building process work? The cell follows a specific code to pick the right amino acid at the right time. Most living things use a standard set of 20 amino acids. However, two others can be used through special mechanisms. These are called selenocysteine and pyrrolysine. Selenocysteine is added when a special sequence called a SECIS element is present. This element tells the cell to use selenocysteine instead of a stop signal. In some tiny organisms, pyrrolysine is added using a different special signal.

Scientists study these molecules to understand how life began and stays healthy. Some researchers believe these specific amino acids were chosen from the "primordial soup" of early Earth. They may have been chosen because they fit into protein chains more easily. Other amino acids were left out because they might be harmful. For example, some can cause a protein to break apart quickly. Others, like canavanine, are toxic because they look like real amino acids and can be used by mistake.

There are many important facts about these molecules. In humans, there are 21 proteinogenic amino acids. We can make 12 of them inside our own bodies. The other nine are called essential amino acids because we must get them from food. These nine are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. We often use single letters to name them, like "W" for tryptophan or "V" for valine.

You can think of these amino acids like different shaped LEGO bricks. To build a sturdy castle, you need specific bricks that snap together perfectly. If you used the wrong shape, the castle might fall down. This is how proteins work in your body. Different amino acids have different properties, like being attracted to water or repelling it. These tiny differences help proteins fold into the exact shapes they need to work.

Proteinogenic amino acids are the fundamental building blocks of life. The term "proteinogenic" literally means "protein creating." These molecules are incorporated biosynthetically into proteins during a cellular process called translation. During translation, a cell reads instructions from RNA to assemble amino acids into long chains. While many different types of amino acids exist in nature, only a small fraction are used to build proteins.

The mechanism of protein synthesis relies on a highly specific genetic code. Most known life forms use a standard set of 20 proteinogenic amino acids. However, two additional amino acids can be incorporated through specialized translation mechanisms. These are selenocysteine and pyrrolysine. In many eukaryotes and prokaryotes, selenocysteine is added when a specific nucleotide sequence called a SECIS element is present. This element directs the cell to treat a UGA codon as a signal for selenocysteine instead of a stop signal. In certain methanogenic prokaryotes, the UAG codon can also be translated to include pyrrolysine.

Amino acids can be categorized by how they are produced and used. Proteinogenic amino acids are those encoded by genes to build proteins. In contrast, non-proteinogenic amino acids are not used in this standard way. Some, like GABA or L-DOPA, are simply not incorporated into proteins. Others, such as hydroxyproline, are created through post-translational modification after a protein is already made. Some non-proteinogenic amino acids are instead used to build nonribosomal peptides. These are synthesized by a different system called non-ribosomal peptide synthetases.

Evolutionary history likely shaped the specific set of amino acids we see today. Some scientists suggest these molecules were selected from the "primordial soup" of early Earth. They may have been chosen because they incorporate into polypeptide chains more effectively than other molecules. Other amino acids may have been excluded because they are chemically unstable. For example, ornithine and homoserine can cause a protein backbone to fragment. Other molecules, such as the arginine analog canavanine, are toxic because they can be mistakenly incorporated into proteins.

In humans, the variety of proteinogenic amino acids is specifically organized. Humans use 21 proteinogenic amino acids, which includes the 20 standard ones plus selenocysteine. Our bodies can synthesize 12 of these from other molecules or metabolic intermediates. The remaining nine must be obtained through our diet. These are known as essential amino acids. They include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Each amino acid possesses unique chemical properties that determine its function. These properties include the mass of the molecule and the behavior of its side chain. For instance, side chains can be hydrophobic, which means they repel water, or polar, which means they interact with water. Some are acidic, while others are basic. The mass of a protein is calculated by adding the masses of its amino acids and then subtracting 18.01524 Da for every peptide bond formed. This subtraction occurs because forming a peptide bond results in the elimination of a water molecule.

Understanding these molecules connects biology to complex chemical systems. The way amino acids interact determines how a protein folds into its final shape. This shape is vital for the protein to perform its biological role. The specific side-chain properties, such as the aromatic rings in phenylalanine or the sulfur in cysteine, allow for diverse chemical reactions. These reactions include the formation of disulfide bonds, which stabilize protein structures in harsh environments. By studying these tiny building blocks, scientists can understand the very foundation of biological complexity.