Amino Acid Chart

Core Concepts

In this tutorial, you will learn about the 20 amino acid structures, along with their important biochemical properties.

Topics Covered in Other Articles

The Amino Acid

Amino acids are the building blocks for polypeptides and proteins. They are important pieces of our bodies and assist in many processes such as protein synthesis. In each amino acid, an amino group and a carboxylic acid group attach to a carbon. However, amino acids are different from each other based on the composition of their R groups.

structure amino acid
Amino acid structure

20 amino acids make up all proteins. To repeat, the only difference in their structures is their R groups. The simplest or smallest amino acid is glycine. In particular, glycine has hydrogen as its R group. Their different side chains are categorized by charge, hydrophobicity (how they react with water), and also polarity. As a result, these three properties affect the way they interact with their surroundings within polypeptides and proteins. This also affects the 3D structure and properties that a protein has.

Amino Acid Chart

The chart below has 21 amino acids. However, selenocysteine is not part of the 20 essential amino acids that are in proteins.

amino acid chart

Amino Acid Side Chains

Amino Acid Hydrophobic Side Chains

The amino acids below all have a side chain that then makes them to be hydrophobic. This property makes them “water fearing” or unable to dissolve in water.

Alanine (Ala) is the first hydrophobic amino acid, and it has low reactivity. This property allows for alanine to create an elongated structure that is equally flexible and stretch resistant.

Alanine structure

Valine (Val) is able to break down into simpler compounds within our bodies.

Valine structure

Isoleucine (Ile) is important when the tertiary structure of a protein it is included in is being determined.

Isoleucine structure

Leucine (Leu) is similar to valine where it is degraded into simpler compounds within the body. However, it is degraded through the use of enzymes.

Leucine structure

Methionine (Met) prevents the accumulation of fat in the liver and detoxifies wastes and toxins.

Methionine structure

Phenylalanine (Phe) can break down into tyrosine within the body.

Phenylalanine structure

Tryptophan (Trp) can break down in the human gut. Also, it can convert into vitamin B3.

Tryptophan structure

Tyrosine (Tyr) is also an important precursor to vital hormones within our bodies. It is within the adrenal hormones (epinephrine and norepinephrine), the thyroid hormones (thyroxine), and melanin (responsible for hair and skin pigment). Phenylalanine produces tyrosine.

Tyrosine structure

Amino Acid Neutral Side Chains

The amino acids below all have side chains that are polar neutral. This means that their side chains are neither acidic nor basic.

Asparagine (Asn) is responsible for removing ammonia (a toxic chemical) from our bodies.

Asparagine structure

Glutamine (Gln) is the most abundant amino acid in our bodies, and it performs several functions. It is responsible for regulating toxic ammonia and urea in our bodies. The reason glutamine can remove toxic ammonia is because its carboxyl side chain can act as a donor and acceptor for ammonia (this then allows for the safe transport of ammonia in our bodies).

Glutamine structure

Serine (Ser) is involved in biosynthesis of metabolites and is important in the catalytic function of enzymes.

Serine structure

Threonine (Thr) is within reactions in bacteria and metabolic rate in animals. However, the exact effect has not yet been determined.

Threonin - Threonine.svg
Threonine structure

Amino Acid Acidic Side Chains

Aspartic acid (Asp) is water soluble, which then allows it to be near the active sites of enzymes.

Aspartic acid, an amino acid
Aspartic acid structure

Glutamic acid (Glu) is similar to aspartic acid and is highly soluble in water.

Glutamic acid, an amino acid
Glutamic acid structure

Amino Acid Basic Side Chains

Arginine (Arg) is produced when proteins are digested within our bodies, and it is converted into nitric oxide (responsible for relaxing blood vessels).

Arginine, an amino acid
Arginine structure

Histidine (His) within proteins acts as both a proton acceptor and donor. Due to this property, histidine can combine into enzymes involved in the metabolism of proteins, carbohydrates, and nucleic acids.

Histidine, an amino acid
Histidine structure

Lysine (Lys) is in the binding enzymes to coenzymes. It plays an important role in the way that histones function. Specifically, it binds to histone acetyl transferases which alter the transcription of certain genes.

Lysine, an amino acid
Lysine structure

Amino Acids with Special Cases

Cysteine (Cys) is able to form disulfide bridges between to peptide chains and also form loops within a singular chain.

Cysteine, an amino acid
Cysteine structure

Glycine (Gly) is unreactive when it is in proteins. The biosynthesis of serine (amino acid), purines, heme (part of hemoglobin found in the blood), and also glutathione (coenzyme) all require glycine.

Glycine, an amino acid
Glycine structure

Proline (Pro) is made from glutamic acid. When it is in a protein it causes sharp bends to occur in the peptide chain, altering the protein’s final structure

Proline, an amino acid
Proline structure

Further Reading