Boldface terms within a definition are also defined in this glossary.

Figures and tables that illustrate defined terms are noted in parentheses.

F₀F₁ complex See ATP synthase.

facilitated transport Protein-aided transport of an ion or small molecule across a cell membrane down its concentration gradient at a rate greater than that obtained by simple diffusion; also called facilitated diffusion. (Table 11-1)

FAD (flavin adenine dinucleotide) A small organic molecule that functions as an electron carrier by accepting two electrons from a donor molecule and two H⁺ from the solution. (Figure 2-33b)

fatty acid Any long hydrocarbon chain that has a carboxyl group at one end; a major source of energy during metabolism and a precursor for synthesis of phospholipids, triglycerides, and cholesteryl esters. (Figure 2-21; Table 2-4)

fermentation The conversion of some of the energy in organic molecule nutrients such as glucose into ATP via their oxidation into organic molecule “waste” products such as lactic acid or ethanol, typically involving the simultaneous cyclical reduction and oxidation of NAD⁺/NADH.

FG-nucleoporins Proteins on the inner surface of the nuclear pore complex with a globular domain that forms part of the pore structure and a random coil domain of hydrophilic amino acids punctuated by short repeats rich in phenylalanine and glycine. (Figure 8-20)

fibroblast A common type of connective tissue cell that secretes collagen and other components of the extracellular matrix; migrates and proliferates during wound healing and in tissue culture.

fibronectin An abundant multi-adhesive matrix protein that occurs in numerous isoforms, generated by alternative splicing, in various cell types. Binds many other components of the extracellular matrix and to integrin adhesion receptors. (Figure 20-33)

FISH See fluorescence in situ hybridization.

flagellum (pl. flagella) Long locomotory structure (usually one per cell) extending from the surface of some eukaryotic cells (e.g.,sperm), whose whiplike bending propels the cell through a fluid medium. Bacterial flagella are smaller and much simpler structures. See also axoneme and cilium. (Figure 18-31)

flavin adenine dinucleotide See FAD.

flippase Protein that facilitates the movement of membrane lipids from one leaflet to the other leaflet of a phospholipid bilayer. (Figure 11-15)

fluorescence in situ hybridization (FISH) Any of several related techniques for detecting specific DNA or RNA sequences in cells and tissues by treating samples with fluorescent probes that hybridize to the sequence of interest and observing the samples by fluorescence microscopy.

fluorescent staining General technique for visualizing cellular components by treating cells or tissues with a fluorescent dye–labeled agent (e.g., antibody) that binds specifically to a component of interest and observing the sample by fluorescence microscopy.

free energy (G) A measure of the potential energy of a system, which is a function of the enthalpy (H) and entropy (S).

functional complementation Procedure for screening a DNA library to identify the wild-type gene that restores the function of a defective gene in a particular mutant. (Figure 6-16)