What type of amino acid is proline

In the dipolar form, the amino group is protonated, and the carboxyl group is deprotonated. The ionization state of an amino acid varies with pH [10]. A series of amino acids joined by peptide bonds form a polypeptide chain, and each amino acid unit in a peptide is called a residue.

Two amino acids can undergo a Condensation reaction to form a dipeptide, accompanied by the loss of a water molecule [11]. The common amino acids are grouped according to their side chains [12].

For example, acidic, basic, uncharged polar, and non-polar. For acidic side chains, the amino acids are: Aspartic acid D and Glutamic acid E formed by the addition of a proton to the amino acids aspartate and glutamate.

Proline is also known as an amino acid. It is not essential to the human diet since it can be synthesized in the body from glutamic acid [13]. Unlike other amino acids that exist in the transform in polypeptides , proline can exist in the cis-form in peptides. Proline is the only cyclic amino acid. This is due to Proline having an odd, cyclic structure when it forms peptide bonds, it induces a bend in the amino acid chain.

Therefore, proline is also known as alpha helix breaker the other alpha helix breaker is Glycine [15]. During the translation of mRNA , amino acids bind to the ribosome as it reads the mRNA and using the information given it produces a specific amino acid sequence by forming peptide bonds between the carboxyl group of one amino acid and the amino group of another via a condensation reaction.

This produces a polypeptide chain. The amino acid Cysteine has many applications and plays an important role in protein structure. This is mainly due to its thiol group. The thiol made up of a sulphur and hydrogen atom is very susceptible to oxidation , allowing cysteine to form disulphide bonds with other molecules including other cysteines.

The resulting product of two linked cysteines is called cystine. When bound to other cysteines, the disulphide bond greatly increases the stability of the protein. However, as this is an oxidation reaction, it is exclusive to extracellular proteins with a few exceptions.

This is because the inside of the cell is highly reducing making the disulphide bond highly unstable. Aromatic Amino acids are the largest of the amino acids and include; phenylalanine F , tyrosine Y and tryptophan W. They can all absorb ultra-violet light however some can absorb more than others, tyrosine and tryptophan absorb more than phenylalanine meaning that tryptophan is the main molecule which absorbs light in the protein.

Aromatic amino acids are also hydrophobic so are located in the core of the protein ensuring they are not near water. Humans cannot synthesize phenylalanine or tryptophan, and can only make tyrosine from phenylalanine, this means that aromatic amino acids are a vital component of our diet as we require them in certain proteins but do not synthesize them ourselves.

Aromatic amino acids contain an aromatic ring [17]. Phenylalanine deficiency can cause confusion, depression, lack of energy and decreased alertness. It can be bought in a tablet form to supplement any deficiency [18]. An inability to break down excess phenylalanine is called Phenylketonuria. To combat this a low phenylalanine diet is used and avoids aspartame sweeteners which resemble phenylalanine and can break down to produce it.

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Contents 1 Amino acid structure 1. Nutrient digestion and absorption. Medical Physiology. Philadelphia, PA: Elsevier; chap Dietzen DJ. Amino acids, peptides, and proteins. In: Rifai N, ed. St Louis, MO: Elsevier; chap Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein and amino acids.

J Am Diet Assoc. PMID: pubmed. Editorial team. Amino acids. The human body uses amino acids to make proteins to help the body: Break down food Grow Repair body tissue Perform many other body functions Amino acids can also be used as a source of energy by the body.