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Unformatted text preview: N NAD (nicotinamide adenine dinucleotide) A * coenzyme, derived from the B vitamin * nicotinic acid, that participates in many biological dehydrogenation reactions. NAD is characteristically loosely bound to the enzymes concerned. It normally car- ries a positive charge and can accept one hydrogen atom and two electrons to be- come the reduced form, NADH. NADH is generated during the oxidation of food, especially by the reactions of the * Krebs cycle. It then gives up its two electrons (and single proton) to the * electron trans- port chain, thereby reverting to NAD + and generating three molecules of ATP per molecule of NADH. NADP ( nicotinamide adenine dinu- cleotide phosphate ) differs from NAD only in possessing an additional phos- phate group. It functions in the same way as NAD although anabolic reactions ( see anabolism ) generally use NADPH (re- duced NADP) as a hydrogen donor rather than NADH. Enzymes tend to be speci Ü c for either NAD or NADP as coenzyme. nadir The point opposite the * zenith on the * celestial sphere. NAND circuit See logic circuits . nano- Symbol n. A pre Ü x used in the metric system to denote 10 –9 . For exam- ple, 10 –9 metre = 1 nanometre (nm). nanoarray See microarray . nanotechnology The development and use of devices that have a size of only a few nanometres. Research has been car- ried out into very small components, which depend on electronic effects and may involve movement of a countable number of electrons in their action. Such devices would act much faster than larger components. Considerable interest has been shown in the production of struc- tures on a molecular level by suitable se- quences of chemical reactions. It is also possible to manipulate individual atoms on surfaces using a variant of the * atomic force microscope. nanotube See buckminsterfullerene . napalm A substance used in incendiary bombs and Û ame throwers, made by forming a gel of petrol with aluminium soaps (aluminium salts of long-chain car- boxylic acids, such as palmitic acid). naphtha Any liquid hydrocarbon or mixture obtained by the fractional distil- lation of petroleum. It is generally ap- plied to higher * alkane fractions with nine or ten carbon atoms. Naphtha is used as a solvent and as a starting ma- terial for * cracking into more volatile products, such as petrol. naphthalene A white volatile solid, C 10 H 8 (see formula); r.d. 1.025; m.p. 80.55 ° C; b.p. 218 ° C. Naphthalene is an aromatic hydrocarbon with an odour of mothballs and is obtained from crude oil. It is a raw material for making certain synthetic resins. α or 1 position β or 2 position Naphthalene naphthols Two phenols derived from naphthalene with the formula C 10 H 7 OH, differing in the position of the –OH group....
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This note was uploaded on 05/29/2009 for the course CIVIL ENG 12345 taught by Professor Xhfxfh during the Spring '09 term at Amirkabir University of Technology.
- Spring '09