| acicula | Origin: L, a small needle, dimin. Of acus needle. One of the needlelike or bristlelike spines or prickles of some animals and plants; also, a needlelike crystal. Source: Websters Dictionary (01 Mar 1998) |
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| acicular | <botany> Resembling a needle (typically used to describe the leaf of a plant). (06 May 1997) |
| aciculate | <botany> Used to describe a plant part which is finely scored on the surface, as if scratched by a pin. (09 Oct 1997) |
| aciculite | <chemical> Needle ore. Source: Websters Dictionary (01 Mar 1998) |
| acid | <chemical, chemistry> A fundamental category of many compounds whose water-based solutions have a sour taste, turn blue litmus paper red and can combine with metals to form salts. They are chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Specific types of acids include: Arrhenius acid: any chemical that increases the number of free hydrogen ions (H+) when added to a water-based solution. The more free hydrogens produced, the stronger the acid. Bronsted or Bronsted-Lowry acid: any chemical that acts as a proton donor in a chemical reaction. Lewis acid: any chemical that accepts two electrons to form a covalent bond during a chemical reaction. (13 Nov 1997) |
| acid agglutination | The clumping together of certain microorganisms at high hydrogen ion concentration. (05 Mar 2000) |
| acid anhydride hydrolases | <enzyme> A group of enzymes that catalyze the hydrolysis of diphosphate bonds in compounds such as nucleoside di- and tri-phosphates, and sulfonyl-containing anhydrides such as adenylylsulfate. (enzyme nomenclature, 1992). Registry number: EC 3.6 (12 Dec 1998) |
| acid carboxypeptidase | <enzyme> Carboxypeptidase z (scpz gene product) isolated from absidia zychae Registry number: EC 3.4.16.1 Synonym: carboxypeptidase w, carboxypeptidase yscy, carboxypeptidase cpd-s3, ybr1015 gene product, carboxypeptidase z, scpz gene product (26 Jun 1999) |
| acid cell | One of the cell's of the gastric glands; it lies upon the basement membrane, covered by the chief cell's, and secretes hydrochloric acid that reaches the lumen of the gland through fine intracellular and intercellular canals (canaliculi). Synonym: acid cell, oxyntic cell. (05 Mar 2000) |
| acid cholesterol ester synthetase | <enzyme> Aortal enzyme, does not require exogenous ATP or CoA; reverse reaction of cholesterol esterase Registry number: EC 3.1.1.- Synonym: cholesterol ester synthetase (26 Jun 1999) |
| acid deoxyribonuclease | An endonuclease that cleaves both strands of native DNA (as well as single-stranded DNA) to produce a mixture of oligodeoxynucleotides, each ending in a 3'-phosphate. Synonym: acid deoxyribonuclease. (05 Mar 2000) |
| acid dextran | The product of acid and heat treatment of dextran. (05 Mar 2000) |
| acid dextrin | The product of acid and heat treatment of dextrin. (05 Mar 2000) |
| acid dissociation constant | <chemistry> This is the equilibrium constant for the breaking apart of a weak acid into its hydrogen and conjugate base in a water solution. (09 Oct 1997) |
| acid dyspepsia | Dyspepsia associated with excess gastric acidity. (05 Mar 2000) |