Learning ObjectiveDescribe the framework of one amino acid and also the functions that confer its certain properties
Key PointsEach amino acid has a main C atom, one amino team (NH2), a carboxyl team (COOH), and also a particular R group.The R team determines the characteristics (size, polarity, and also pH) because that each kind of amino acid.Peptide bonds type between the carboxyl team of one amino acid and also the amino group of one more through dehydration synthesis.A chain the amino mountain is a polypeptide.

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TermspolypeptideAny polymer the (same or different) amino mountain joined via peptide bonds.R groupThe R group is a next chain certain to each amino acid that confers certain chemical properties to that amino acid.amino acidAny the 20 naturally developing α-amino acids (having the amino, and carboxylic acid groups on the very same carbon atom), and a selection of next chains, that combine, via peptide bonds, to kind proteins.

Structure of an Amino Acid

Amino acids space the monomers that comprise proteins. Every amino acid has the same basic structure , which is composed of a central carbon atom, also known as the alpha (α) carbon, external inspection to an amino team (NH2), a carboxyl group (COOH), and to a hydrogen atom. In the aqueous atmosphere of the cell, the both the amino group and the carboxyl group are ionized under physiological conditions, and so have the frameworks -NH3+ and also -COO–, respectively. Every amino acid likewise has an additional atom or team of atoms bonded to the central atom recognized as the R group. This R group, or side chain, offers each amino acid proteins specific characteristics, including size, polarity, and pH.

Amino mountain structureAmino acids have actually a central asymmetric carbon come which one amino group, a carboxyl group, a hydrogen atom, and also a next chain (R group) space attached. This amino acid is unionized, however if it were put in water at pH 7, the amino group would choose up one more hydrogen and also a hopeful charge, and also the hydroxyl in the carboxyl group would lose and also a hydrogen and gain a negative charge.

Types the Amino Acids

The surname “amino acid” is derived from the amino group and also carboxyl-acid-group in their an easy structure. There room 21 amino acids present in proteins, each v a particular R group or next chain. Ten of these are taken into consideration essential amino acids in humans since the human body cannot create them and they must be obtained from the diet. All organisms have various essential amino acids based on their physiology.

Types of amino acidsThere are 21 common amino acids frequently found in proteins, each with a different R team (variant group) the determines its chemical nature. The 21st amino acid, not presented here, is selenocysteine, v an R team of -CH2-SeH.

Characteristics of Amino Acids

Which category of amino acid would certainly you mean to discover on the surface ar of a soluble protein, and which would you mean to uncover in the interior? What distribution of amino acids would certainly you expect to find in a protein installed in a lipid bilayer?

The chemical composition the the next chain identify the features of the amino acid. Amino acids such as valine, methionine, and alanine are nonpolar (hydrophobic), when amino acids such together serine, threonine, and cysteine are polar (hydrophilic). The next chains that lysine and also arginine room positively fee so this amino acids are also known as straightforward (high pH) amino acids. Proline is an exemption to the standard framework of an animo acid because its R team is linked to the amino group, forming a ring-like structure.

Amino acids are represented by a solitary upper case letter or a three-letter abbreviation. Because that example, valine is known by the letter V or the three-letter price val.

Peptide Bonds

The sequence and also the number of amino acids ultimately determine the protein’s shape, size, and also function. Each amino acid is attached to another amino mountain by a covalent bond, recognized as a peptide bond. Once two amino acids are covalently attached by a peptide bond, the carboxyl team of one amino acid and the amino team of the incoming amino mountain combine and release a molecule of water. Any reaction that combines two monomers in a reaction that generates H2O as one of the commodities is well-known as a dehydration reaction, therefore peptide bond development is an example of a dehydration reaction.

Peptide link formationPeptide bond formation is a dehydration synthetic reaction. The carboxyl team of one amino mountain is attached to the amino group of the incoming amino acid. In the process, a molecule that water is released.

Polypeptide Chains

The result chain of amino mountain is called a polypeptide chain. Each polypeptide has a complimentary amino group at one end. This finish is dubbed the N terminal, or the amino terminal, and also the other finish has a cost-free carboxyl group, also known as the C or carboxyl terminal. Once reading or report the amino mountain sequence of a protein or polypeptide, the convention is to usage the N-to-C direction. That is, the very first amino mountain in the succession is assumed come the it is in one in ~ the N terminal and the last amino acid is assumed to it is in the one in ~ the C terminal.

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Although the terms polypeptide and also protein are sometimes used interchangeably, a polypeptide is technically any polymer the amino acids, vice versa, the term protein is offered for a polypeptide or polypeptides that have actually folded properly, combined with any added components essential for proper functioning, and also is now functional.


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