Amino acid | Definition, Structure, & Facts | Britannica
2024年11月15日 · Amino acid, any of a group of organic molecules that consist of a basic amino group, an acidic carboxyl group, and a unique organic side chain. The term amino acid is short for α-amino [alpha-amino] carboxylic acid. Examples of amino acids include glycine and threonine.
Protein - Amino Acids, Structure, Function | Britannica
2024年11月15日 · Although more than 100 amino acids occur in nature, particularly in plants, only 20 types are commonly found in most proteins. In protein molecules the α-amino acids are linked to each other by peptide bonds between the amino group of one amino acid and the carboxyl group of its neighbor.
Amino acid - Building Blocks, Structure, Functions | Britannica
2024年11月15日 · Amino acid - Building Blocks, Structure, Functions: One of the most useful manners by which to classify the standard (or common) amino acids is based on the polarity (that is, the distribution of electric charge) of the R group (e.g., side chain).
Amino acid - Reactions, Structure, Synthesis | Britannica
2024年11月15日 · Amino acid - Reactions, Structure, Synthesis: Amino acids via their various chemical functionalities (carboxyls, amino, and R groups) can undergo numerous chemical reactions. However, two reactions (peptide bond and cysteine oxidation) are of particular importance because of their effect on protein structure.
Structure and properties of amino acids | Britannica
amino acid, Any of a class of organic compounds in which a carbon atom has bonds to an amino group (―NH 2), a carboxyl group (―COOH), a hydrogen atom (―H), and an organic side group (called ―R). They are therefore both carboxylic acids and amines. The physical and chemical properties unique to each result from the properties of the R ...
Protein | Definition, Structure, & Classification | Britannica
2024年11月15日 · A protein molecule is very large compared with molecules of sugar or salt and consists of many amino acids joined together to form long chains, much as beads are arranged on a string. There are about 20 different amino acids that occur naturally in proteins.
Genetic code | Definition, Characteristics, Table, & Facts | Britannica
2024年11月15日 · genetic code, the sequence of nucleotides in deoxyribonucleic acid and ribonucleic acid that determines the amino acid sequence of proteins. Though the linear sequence of nucleotides in DNA contains the information for protein sequences, proteins are not made directly from DNA.
Codon | Definition, Function, & Examples | Britannica
codon, in genetics, any of 64 different sequences of three adjacent nucleotides in DNA that either encodes information for the production of a specific amino acid or serves as a stop signal to terminate translation (protein synthesis). Codons are made up of any triplet combination of the four nitrogenous bases adenine (A), guanine (G), cytosine ...
Alanine | Amino Acid, Protein, Metabolism | Britannica
alanine, either of two amino acids, one of which, L-alanine, or alpha-alanine (α-alanine), is a constituent of proteins. An especially rich source of L-alanine is silk fibroin, from which the amino acid was first isolated in 1879.
Glycine | Building Blocks, Protein Synthesis & Metabolism | Britannica
2024年11月15日 · Glycine, the simplest amino acid, obtainable by hydrolysis of proteins. Sweet-tasting, it was among the earliest amino acids to be isolated from gelatin (1820). Especially rich sources include gelatin and silk fibroin.