Amino acid | Definition, Structure, & Facts | Britannica
2024年10月21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.
Amino acid - Building Blocks, Structure, Functions | Britannica
2024年10月21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).
Protein - Amino Acids, Structure, Function | Britannica
2024年11月6日 · Structures of common amino acids. The amino acids present in proteins differ from each other in the structure of their side (R) chains. The simplest amino acid is glycine, in which R is a hydrogen atom. In a number of amino acids, R …
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 ...
Amino acid - Reactions, Structure, Synthesis | Britannica
2024年10月21日 · 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.
Genetic code | Definition, Characteristics, Table, & Facts | Britannica
2024年10月1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.
Protein | Definition, Structure, & Classification | Britannica
2024年11月6日 · A protein is a naturally occurring, extremely complex substance that consists of amino acid residues joined by peptide bonds. Proteins are present in all living organisms and include many essential biological compounds such as enzymes, , and antibodies.
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.
Histidine | Essential, Protein, Structure | Britannica
Histidine, an amino acid obtainable by hydrolysis of many proteins. A particularly rich source, hemoglobin (the oxygen-carrying pigment of red blood cells) yields about 8.5 percent by weight of histidine. First isolated in 1896 from various proteins, histidine is …