Author: Glossary
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Salt
Usually refers to sodium chloride, common salt or table salt (chemically any product of reaction between an acid and an alkali is a salt). The main sources are either from mines in areas where there are rich deposits of crystalline salt, or deposits left by the evaporation of sea water in shallow pans (known as…
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Salatrims
Poorly absorbed fats, used as fat replacers; triacylglycerols containing short- and long-chain fatty acids.
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Ribose
A pentose (five-carbon) sugar which occurs as an intermediate in the metabolism of glucose; especially important in the nucleic acids and various coenzymes. D-Ribose, a five-carbon-atom monosaccharide (i.e., a sugar). It is important to life because it and the closely allied compound deoxyribose form a part of the molecules that constitute the backbone of nucleic…
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Rhodopsin
The pigment in the rod cells of the retina of the eye, also known as visual purple, consisting of the protein opsin and retinaldehyde, which is responsible for the visual process. In cone cells of the retina the equivalent protein is iodopsin. A light-sensitive substance found in the rods. A light-sensitive purple pigment in the…
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Rhamnose
A methylated pentose (five-carbon) sugar.
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Rexinoids
Compounds chemically related to vitamin A, that bind to the retinoid X receptor but not the retinoic acid receptor.
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Reverse transcriptase
Viral enzyme that catalyses the conversion of mRNA into cDNA. Also known as RNA-directed DNA polymerases. A class of enzymes first discovered to be present in RNA tumor-virus which allows the synthesis of DNA using the RNA present in the virus as a template. This is the reverse of what normally happens and hence the…
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Retinol-biding protein
A plasma protein which specifically binds retinol (the alcohol form of vitamin A) and prevents it from being excreted. In vitamin A sufficiency, all the RBP is bound to retinol, in a 1:1 complex, but in vitamin A deficiency the protein may become partially desaturated, so that the ratio of protein to retinol then exceeds…
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Retinoids
Compounds chemically related to, or derived from, vitamin A, which display some of the biological activities of the vitamin, but have lower toxicity; they are used for treatment of severe skin disorders and some cancers. A group of biologically active compounds that are chemical derivatives of vitamin A. Among other effects on living cells, some…
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Retinal maculopathy
Deterioration of the macula (central region of the retina) which occurs progressively in older people, thus irreversibly impairing vision. Thought to be exacerbated by pro-oxidant action such as by oxygen free radicals.