| carbon dioxide-free water | Purified water that has been boiled vigorously for 5 minutes or more. (05 Mar 2000) |
|---|---|
| free water | Water in the body that can be removed by ultrafiltration and in which substances can be dissolved. (05 Mar 2000) |
| free water clearance | The amount of water excreted in the urine beyond that which would accompany the excreted solutes if the urine were isosmotic with plasma; it represents the loss of body water in excess of solute tending to raise body osmolality and making urine hyposmotic. Unlike other clearance's, it is calculated by subtracting the osmolal clearance from the actual volume of urine excreted per minute. A negative value for free water clearance represents the amount of water that the body has reclaimed from isosmotic tubule fluid to make the urine hyperosmotic and to lower body osmolality. (05 Mar 2000) |
| membrane-bound proton-translocating PPi synthase | <enzyme> From rhodospirillum rubrum; functions as an alternative coupling factor; n,n'-dicyclohexylcarbodiimide-sensitive; catalyses the phosphorylation of pi to ppi, the hydrolysis of ppi and the concomitant translocation of proton across the plasma membrane Registry number: EC 3.6.1.- Synonym: h(+)-ppi synthase (26 Jun 1999) |
| proton | <physics> An elementary atomic particle with a positive charge and a mass of about 1 amu. (09 Oct 1997) |
| proton acceptor | <chemistry> A base, an anionic substance that acceptsa proton during an acid-basereaction. (09 Oct 1997) |
| proton ATPase | <enzyme> An ion pump that actively transports hydrogen ions across lipid bilayers in exchange for ATP. Major groups are the F-type ATPases, that run in reverse to synthesise ATP in bacterial, mitochondrial and chloroplast membranes (ATP synthase) and the V-type ATPases found in intracellular vesicles with an acidic lumen and on certain epithelial cells (e.g. Kidney intercalated cells). Gastric H/K ATPase is a proton ATPase. (18 Nov 1997) |
| proton donor | <chemistry> An acid, a susbstance that donates protons in an acid-base reduction reaction. (10 Jan 1998) |
| proton-motive force | Energy that is generated by the transfer of protons or electrons across an energy-transducing membrane and that can be used for chemical, osmotic, or mechanical work. Proton-motive force can be generated by a variety of phenomena including the operation of an electron transport chain, illumination of a purple membrane, and the hydrolysis of ATP by a proton atpase. (12 Dec 1998) |
| proton pump | Integral membrane proteins that transport protons across a membrane against a concentration gradient. This transport is driven by hydrolysis of ATP by hydrogen-transporting ATP synthase. (12 Dec 1998) |
| proton pump inhibitor | <pharmacology> A group of anti-ulcer medications which work by binding to H+/K+ ATPase, an enzyme which is found on the secretory surface of parietal cells. It thereby inhibits the final transport of hydrogen ions (via exchange with potasium) into the gastric lumen. Examples of proton pump inhibitors include omeprazole and lansoprazole. (27 Sep 1997) |
| bacteria-free stage of bacterial endocarditis | Endocarditis described prior to the antibiotic era and presumably due to spontaneous healing of the bacterial vegetations. (05 Mar 2000) |
| radical, free | In biochemistry, it is a group of atoms bonded together into an entity that is extremely reactive and shortlived. (a free radical is not a political extremist on parole.) (12 Dec 1998) |
| germ-free animal | An animal which has no microorganisms whatsoever living in or on it. An animal which was born and raised in an isolated environment with no microorganisms in it, such as within a germ-free isolator. (09 Oct 1997) |
| germ-free isolator | A chamber which has absolutely no microorganisms whatsoever living in it, where a germ-free animal can be born and raised. An artificial barrier surrounding a living facility for germ-free animals, which keeps out all microorganisms. (09 Oct 1997) |