Within a protein, multiple amino acids are linked together by peptide bonds, thereby forming a long chain. Peptide bonds are formed by a biochemical reaction that extracts a water molecule as it joins the amino group of one amino acid to the carboxyl group of a neighboring amino acid.

Section 3.2Primary Structure: Amino Acids Are Linked by Peptide Bonds to Form Polypeptide Chains. The formation of a dipeptide from two amino acids is accompanied by the loss of a water molecule (Figure 3.18). The equilibrium of this reaction lies on the side of hydrolysis rather than synthesis.

Peptide bond formation: Peptide bond formation is a dehydration synthesis reaction. The carboxyl group of one amino acid is linked to the amino group of the incoming amino acid. In the process, a molecule of water is released.

Amino acids can be linked by a condensation reaction in which an ―OH is lost from the carboxyl group of one amino acid along with a hydrogen from the amino group of a second, forming a molecule of water and leaving the two amino acids linked via an amide—called, in this case, a peptide bond.

Each amino acid has the same fundamental structure, which consists of a central carbon atom, also known as the alpha (α) carbon, bonded to an amino group (NH2), a carboxyl group (COOH), and to a hydrogen atom.

Every amino acid also has another atom or group of atoms bonded to the central atom known as the R group. This R group, or side chain, gives each amino acid proteins specific characteristics, including size, polarity, and pH.

Amino acids are classified into three groups: Essential amino acids. Nonessential amino acids. Conditional amino acids.

Amino acids can be classified based on the characteristics of their distinctive side chains as nonpolar, polar but uncharged, negatively charged, or positively charged. The amino acids found in proteins are L-amino acids.

At pH=7, two are negative charged: aspartic acid (Asp, D) and glutamic acid (Glu, E) (acidic side chains), and three are positive charged: lysine (Lys, K), arginine (Arg, R) and histidine (His, H) (basic side chains)….Charged side chains.

There are three amino acids that have basic side chains at neutral pH. These are arginine (Arg), lysine (Lys), and histidine (His). Their side chains contain nitrogen and resemble ammonia, which is a base.

An amino acid is an organic molecule that is made up of a basic amino group (−NH2), an acidic carboxyl group (−COOH), and an organic R group (or side chain) that is unique to each amino acid. Each molecule contains a central carbon (C) atom, called the α-carbon, to which both an amino and a carboxyl group are attached.

isoleucine, methionine, serine and valine. All the other amino acids share the initial letters A, G, L, P or T, so arbitrary assignments were made….Table 5. The One-Letter Symbols.

CHEBI:58045 – L-isoleucine zwitterion

l-Isoleucine | C6H13NO2 – PubChem.

So what’s the word? Wikipedia’s says that it’s “Methionylthreonylthreonylglutaminylarginyl isoleucine” (ellipses necessary), which is the “chemical name of titin, the largest known protein.” Also, there’s some dispute about whether this is really a word.

The IUPAC nomenclature for organic chemical compounds is open-ended, giving rise to the 189,819-letter chemical name Methionylthreonylthreonyl… isoleucine for the protein also known as titin, which is involved in striated muscle formation.

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Branched-chain amino acids might also cause stomach problems, including nausea, vomiting, diarrhea, and stomach bloating. In rare cases, branched-chain amino acids may cause high blood pressure, headache, or skin whitening.

‘Polarity’

Role in structure: Being hydrophobic, Isoleucine prefers to be buried in protein hydrophobic cores. However, Isoleucine has an additional property that is frequently overlooked. Like Valine, and Threonine it is C-beta branched.

Role of isoleucine in the body Isoleucine has a role in the detoxification of nitrogenous waste like ammonia, which is then excreted from the body by the kidneys. Isoleucine is also essential for the production and formation of hemoglobin and the production of red blood cells.