118 CHAPTER 4 Sensors at the micro-scale Enzymes: In vivo: Lymphocytes: Macrophages: Polylysine: Streptavidin: Vesicle: Proteins that promote (catalyze) (bio)chemical reactions. For example, the glucose oxidase enzyme promotes glucose (C 6 H 12 O 6 ) conversion to gluconic acid (C 6 H 12 O 7 ). Refers to a biological study that takes place within the living organism. A type of small white blood cell that plays a large role in defending the body against disease. There are two types of lymphocytes: B cells make antibodies to attack bacteria and toxins. T cells attack body cells that have been taken over by viruses or have become cancerous. A type of large white blood cell. Macrophages play an important role in the human immune system by engulfing and ingesting infectious agents (pathogens). Human macrophages are about 20 m m in size. (poly-L-lysine) is a small polymer of the amino acid L-lysine that is produced by bacterial fermentation. A type of protein widely used in molecular biology for detection of various biomolecules. A relatively small intracellular, membrane-enclosed reservoir that stores substances. LIST OF SYMBOLS Symbol A c vol C th d e E b f I, i k k B L, l l cell n at n e n s N 0 N a N A N mol Meaning Area Volumetric heat capacity Thermal capacitance Diameter Electron charge, e ¼ 1.6 Â 10 À19 C Energy barrier height Frequency Current Number of trials Boltzmann constant, k B ¼ 1.38 Â 10 ­23 J/K Length Cell size Atomic concentration Concentration of electrons Surface charge concentration Number of electrons that strike barrier per unit time Concentration of ionized acceptor impurities in semiconductor NW Avogadro's Number, N A ¼ 6.022 Â 10 23 mol À1 Number of molecules