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/əˌkäməˈdāSHən/ Noun 1. The process by which the vertebrate eye changes optical power to maintain a clear image (focus) on an object as its distance varies. Accommodation acts like a reflex, but can also be consciously controlled. ( 2. (Ophthalmology, Physiology) Adjustment, especially that of the eye for various distances resulting in pupil constriction or dilatation. ( 3. The automatic adjustment of the focus of the eye by flattening or thickening of the lens. (Google dictionary) Word origin: From Latin accommodātiō (“adjustment, accommodation, compliance”), from accommodō (“adapt, put in...

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Acetyl coenzyme A

Noun 1. A compound, C25H38N7O17P3S, that functions as a coenzyme in many biological acetylation reactions and is formed as an intermediate in the oxidation of carbohydrates, fats, and proteins. Also called acetyl-coA. ( 2. An important molecule in metabolism, used in many biochemical reactions. Its main function is to convey the carbon atoms within the acetyl group to the citric acid cycle (Krebs cycle) to be oxidized for energy production. ( 3. Acetyl CoA participates in the biosynthesis of fatty Acids and sterols, in the oxidation of fatty acids and in the metabolism of many amino acids. It also acts as a biological acetylating agent....

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Acetylcholine (Ach)

/əˌsētlˈkōˌlēn/  /ˌasitl-/ 1. An organic, polyatomic cation that acts as a neurotransmitter in both the peripheral nervous system (PNS) and central nervous system (CNS) in many organisms including humans. ( 2. Acetylcholine is one of many neurotransmitters in the autonomic nervous system (ANS) and is the only neurotransmitter used in the motor division of the somatic nervous system (sensory neurons use glutamate and various peptides at their synapses). Acetylcholine is also the principal neurotransmitter in all autonomic ganglia. ( 3. (Biochemistry) A neurotransmitter in humans and other animals. It is an ester of acetic acid and choline with chemical formula CH3COOCH2CH2N+(CH3)3. ( 4. (Chemical, Neurology, physiology) A chemical found in vertebrate neurons that carries information across the synaptic cleft, the space between two nerve cells. ( 5. A compound that occurs throughout the nervous system, in which it functions as a neurotransmitter. (Google...

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Noun 1. (Science: cell biology) A filamentous proteins (42 kD) involved in muscle contraction in both smooth and striated muscle and also serves as an important structural molecule for the cytoskeleton of many eukaryotic cells. ( 2. A globular, roughly 42-kDa multi-functional protein found in all eukaryotic cells (the only known exception being nematode sperm), where it may be present at concentrations of over 100 μM. ( 3. One of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans. Actin is the monomeric subunit of two types of filaments in cells: microfilaments, one of the three major components of the cytoskeleton, and thin filaments, part of the contractile apparatus in muscle cells. Thus, actin participates in many important cellular processes, including muscle contraction, cell motility, cell division and cytokinesis, vesicle and organelle movement, cell signaling, and the establishment and maintenance of cell junctions and cell shape. ( 4. Filamentous Proteins that are the main constituent of the thin filaments of Muscle fibers. The filaments (known also as filamentous or F-actin) can be dissociated into their globular subunits; each subunit is composed of a single polypeptide 375 Amino Acids long. This is known as globular or G-actin. In conjunction with Myosins, actin is responsible for the contraction and Relaxation of Muscle. ( 5. A protein found in all eukaryotic cells, forming...

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