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Noun, pl. facets (Anatomy) 1. A smooth circumscribed surface. ( (Entomology) 1. One member of a compound eye, as found in insects and crustaceans. ( 2. Any of the individual units (ommatidia) that make up the compound eye of an insect or crustacean. (Google Dictionary) Word origin: From French facette (12c., Old French facete), diminutive of face. The diamond-cutting sense is the original...

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Facilitated diffusion

1. A process of passive transport (as opposed to active transport), with this passive transport aided by integral membrane proteins. It is the spontaneous passage of molecules or ions across a biological membrane passing through specific transmembrane integral proteins. The facilitated diffusion may occur either across biological membranes or through aqueous compartments of an organism. Polar molecules and charged ions are dissolved in water but they cannot diffuse freely across the plasma membrane due to the hydrophobic nature of the fatty acid tails of phospholipids that make up the lipid bilayers. ( 2. Transport of substances across a biological membrane from an area of higher concentration to an area of lower concentration by means of a carrier molecule. Since the substances move along the direction of their concentration gradients, energy is not required. ( Syn: facilitated transport, passive-mediated...

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Facultative parasite

1. An organism that may resort to parasitic activity, but does not absolutely rely on any host for completion of its life cycle. ( 2. A parasite that does not live exclusively on a given host species. ( 3. An organism that normally lives as a saprophyte but under certain conditions can live as a parasite. ( 4. An organism that lives independent of a host but may occasionally be parasitic under certain conditions....

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