Glossary for NanoBiotechnology

A-kinase (cyclic AMP-dependent protein kinase):
Enzyme that phosphorylates target proteins in response to a rise in intracellular cyclic AMP. First identified in skeletal muscle as part of the pathway of regulation of glycogen breakdown in response to adrenaline.

ABC transporters:
Members of a large superfamily of membrane transport proteins that hydrolyze ATP and transfer a diverse array of small molecules across a membrane.

acetyl: Chemical group derived from acetic acid. Acetyl groups are important in metabolism and often added as a covalent modification of proteins.

acetyl CoA: Small water-soluble molecule that carries acetyl groups in cells. Comprises an acetyl group linked to coenzyme A (CoA) by an easily hydrolyzable thioester bond. acetylcholine: Neurotransmitter that functions at cholinergic chemical synapses, found both in the brain and in the peripheral nervous system. It is the neurotransmitter at vertebrate neuromuscular junctions. acetylcholine receptor: Ion channel that opens in response to acetylcholine binding, thereby converting a chemical signal into an electrical one. Best understood example of a ligand-gated channel. Sometimes called the nicotinic acetylcholine receptor to distinguish it from a muscarinic receptor, which is a G-protein-linked cell-surface receptor. acrosomal process: Long, thin, actin-containing spike produced from the head of certain sperm when they make contact with the egg. Seen in sea urchins and other marine invertebrates whose eggs are surrounded by a thick gelatinous coat. acrosome: Region at the head end of a sperm cell that contains a sac of hydrolytic enzymes used to digest the protective coating of the egg. actin: Abundant protein that forms actin filaments in all eucaryotic cells. The monomeric form is sometimes called globular or G-actin; the polymeric form is filamentous or F-actin. actin-binding protein: Protein that associates with either actin monomers or actin filaments in cells and modifies their properties. Examples include myosin, a-actinin, and profilin. actin filament (microfilament): Helical protein filament formed by the polymerization of globular actin molecules. A major constituent of the cytoskeleton of all eucaryotic cells and part of the con- tractile apparatus of skeletal muscle. action potential: Rapid, transient, self-propagating electrical excitation in the plasma membrane of a cell such as a neuron or muscle cell. Action potentials, or nerve impulses, allow long-distance signaling in the nerveous system. activation energy: Extra energy that must be possessed by atoms or molecules in addition to their ground-state energy in order to undergo a particular chemical reaction. active site: Region of an enzyme surface to which a substrate molecule binds in order to undergo a catalyzed reaction. active transport: Movement of a molecule across a membrane or other barrier driven by energy other than that stored in the concentration gradient or electrochemical gradient of the transported molecule.

acyl group: Functional group derived from a carboxylic acid. (R represents an alkyl group, such as methyl.)

Parts of the glossary are from the following book:
Copyright 1983, 1989, 1994 From "Molecular Biology of the Cell" by Bruce Alberts, Dennis Bray, Julian Lewis, Martin Raff, Keith Roberts, James D. Watson. Reproduced by permission of Routledge, Inc., part of The Taylor & Francis Group.