Category: R

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…

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…

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…

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.  

Vitamers of vitamin A.  

Immature precursor of the red blood cell in which the remains of the nucleus are visible as a reticulum. Very few are seen in normal blood as they are retained in the marrow until mature, but on remission of anaemia, when there is a high rate of production, reticulocytes appear in the bloodstream (reticulocytosis). Immature…

Ratio of the volume of carbon dioxide produced when a substance is oxidised, to the volume of oxygen used. The oxidation of carbohydrate results in an RQ of 1.0; of fat, 0.7; and of protein, 0.8. Ratio of the amount of carbon dioxide produced to the amount of oxygen consumed at cellular level. The ratio…

Concentration of a compound in the blood above which it is not reabsorbed by the kidney, and so is excreted in the urine. Concentration of a substance in plasma at which it is excreted in urine. The concentration at which a substance in the blood normally not excreted by the kidney begins to appear in…

Rate of passage of plasma through the kidneys, directly related to glomerular filtration rate.  

A measure of protein quality.