Online Biology Dictionary - F

F (1) phenylalanine; (2) fluorine; (3) Fahrenheit.

F factor (short for fertility factor also sex factor or F plasmid) A plasmid allowing bacteria to form sex pili and, therefore, to carry out DNA transfers during conjugation. SEE A DIAGRAM EXPLAINING F-FACTOR TRANSFER

F₁ generation The first filial generation, the generation produced by the crossing of two distinct types of parents. MORE INFORMATION

F1P Fructose-1-phosphate.

F₂ generation The second filial generation, the generation produced by interbreeding of individuals belonging to the F₁ generation. In general, the F_n generation is produced by interbreeding of individuals belonging to the F_n-1 generation. MORE INFORMATION

F6P Fructose-6-phosphate.

Fab Either of the antigen-binding portions of an antibody (Fab = "fragment, antigen-binding").

facial muscles Click here to see a labeled illustration of the muscles of the human face.

facilitated diffusion Diffusion of molecules across a plasma membrane with the assistance of carrier proteins (the term facilitated diffusion is used in opposition to passive transport).

faciocervical Pertaining to the face and neck.

FACS Fluorescence-activated cell sorter. See: flow cytometry.

facultative anaerobe /AN-uh-robe/ An organism that engages in aerobic respiration when oxygen is present, but relies on fermentation in the absence of oxygen.

FAD Flavin adenine dinucleotide.

FADH2 Reduced form of flavin adenine dinucleotide.

fallopian tubes /fuh-LOHP-ee-uhn/ Ducts by which ova pass from the ovaries to the uterus.

family In taxonomy, a division of an order that itself contains one or more genera. CHART OF RELATIVE TAXONOMIC RANKS

fat A triacylglycerol ester of a fatty acid. During hydrolysis, fats are broken down into glycerol and triacylglycerols, a process that provides energy to cellular tissues.

fatty acid Any molecule produced by replacing one of the hydrogen atoms of a hydrocarbon with a carboxyl group.

fauces /FAW-seez/ The region where the mouth interfaces with the pharynx.

faucial reflex /FAW-see-uhl/ Gagging caused by contact with the fauces.

faucitis /fuh-SIGHT-uhs/ Inflammation of the fauces.

fauna /FAWN-uh/ The animal life, as opposed to plant life (flora), of an era, geographic region, or biome. See biota.

FBP Fructose-1,6-bisphosphate.

FBPase Fructose bisphosphatase.

Fd Ferredoxin.

febrile /FEB-bruhl, FEEB-, -brial/ Feverish.

febris Fever.

feces (only used in plural) /FEE-seez/ Excrement (bodily waste ejected from the intestines).

fecula (pl feculae) /FEK-yuh-luh/ Sediment.

feedback inhibition A condition in which a process producing a particular product tends to occur at a slower rate when that product is present at high concentration.

Felidae /FELL-uh-DEE/ The mammalian family that contains the cats.

femorotibial /fuh-MORE-oh-TIB-ee-uhl/ Pertaining to the femur and the tibia.

femur /FEE-mer/ (1) in humans, the largest bone in the body; it connects the knee and hip; (2) in animals, the bone of the proximal portion of the hind limb. ANTERIOR VIEW OF HUMAN FEMUR  POSTERIOR VIEW OF HUMAN FEMUR

fermentation A catabolic process that produces a characteristic product such as lactic acid or ethanol. Without an electron transport chain, fermentation makes a limited amount of ATP from glucose. See: respiration.

ferredoxins (Fd) Iron-sulfur proteins mediating electron transfer. There are many different types of ferredoxins that participate in a wide variety of metabolic reactions.

fertility factor See: F factor.

fertilization The union of a male and a female gamete to form a zygote.

fetotoxic /FEET-oh-TAWK-sick/ Toxic to the fetus within the uterus.

fetus (also foetus or fœtus) /FEET-uhs/ A developing mammal, or other viviparous vertebrate, after the embryonic stage and before birth.

FH Familial hypercholesterolemia.

fibroblast /FIBE-roh-blast/ A cell that secretes the necessary constituents of extracellular fibers.

fibula /FIB-yuh-luh, -yoo-luh/ A long, slender bone located on the lateral side of the tibia; in humans: the calf bone. PICTURE

fibulocalcaneal /FIB-yuh-low-cal-CANE-ee-uhl/ Pertaining to the fibula and calcaneus.

filamentous /fil-uh-MENT-uhs/ Thready, threadlike; also: bearing or covered with threadlike structures ("filaments").

filial generation /FILL-ee-uhl/ See: F₁ generation and F₂ generation.

filiferous Thread-bearing.

filiform Thread-shaped.

finger protein A protein with a zinc finger that allows the protein to bind DNA. A zinc finger has the consensus sequence Cys-X_2-4-Cys-X₃-Cys-Phe-X₅-Leu-X₂-His-X₃-His.
The motif is named for the finger-like loop of amino acids that protrudes from the zinc binding site (known as the "Cys₂/His₂ finger" (pronounced "siss-two-hiss-two").

fingerprinting In genetics, the identification of multiple specific alleles uniquely identifying an individual. Also known as DNA fingerprinting.

finished DNA sequence High-quality, low error, gap-free DNA sequence of the human genome. Achieving this ultimate 2003 HGP goal requires additional sequencing to close gaps, reduce ambiguities, and allow for only a single error every 10,000 bases, the agreed-upon standard for HGP finished sequence. See also: sequencing, draft sequence.

FISH See: fluorescence in situ hybridization.

flabellum /fluh-BELL-uhm/ A fan-shaped part.

flaccid /FLA-suhd/ Lacking tension; said of walled cells in an isotonic environment.

flagellin /fluh-JEHL-uhn/ The main protein component of bacterial flagella.

flagellum (pl flagella) /fluh-GEHL-uhm/ A threadlike motile process serving in locomotion. See: undulipodium.

flanking DNA The DNA sequences on either side of a given region of the genome.

flatworm A flat worm belonging to the phylum Platyhelminthes.

flavescent Yellowish.

flavin adenine dinucleotide (FAD) A redox cofactor that exists in both a reduced and oxidized state. In the oxidized state (FAD⁺) it accepts electrons and becomes reduced, then, in its reduced state (FADH2), it acts as a reducing agent, donating electrons. Many oxidoreductases (known as "flavoenzymes") will function only when FAD is present.

flavin mononucleotide (FMN) or riboflavin-5'-phosphate, is the usual form in which riboflavin (vitamin B₂) is found in cells. It functions as a prosthetic group in conjunction with oxidoreductases such as NADH dehydrogenase. Riboflavin kinase produces FMN from riboflavin.

flavoproteins Dehydrogenases containing flavin. They play a key role in the cellular respiration of plants and animals.

flora /FLORE-uh/ The plant life, as opposed to animal life (fauna), of an era, geographic region, or biome. See biota.

flow cytometry /sigh-TOM-uh-tree)/ Analysis of cells or chromosomes by evaluating their light absorption or fluorescent properties as they stream through a laser beam. A machine that carries out this process is known as a fluorescence-activated cell sorter (FACS).

flow karyotyping Use of flow cytometry to analyze and separate chromosomes.

fluidram A measure of volume used in pharmacology (being the same as the volume of 57.1 grains of distilled water = 3.70 cc).

flukes (1) the two parts or lobes that make up the triangular tail of a whale (now often used in singular to refer to the entire fin, composed of both lobes); (2) flatworms of the class Trematoda.

fluid mosaic model The now-accepted model of eukaryotic cell membrane structure. DESCRIPTION OF THE MODEL

fluorescence in situ hybridization (FISH) A technique that vividly paints chromosomes or portions of chromosomes with fluorescent molecules. It uses fluorescein tags to detect hybridization of probes. The method can be used both with metaphase chromosomes and with interphase chromatin; useful for identifying chromosomal abnormalities and for gene mapping.

fluorescence-activated cell sorter (FACS) See: flow cytometry.

fluorine (F) /FLOO-uh-ree or FLOOR-een/ A gaseous chemical element. Atomic weight 18.9984; atomic number 9. When in its pure elemental form, fluorine bonds with itself to form diatomic fluorine, F₂. However, F₂ is extremely reactive — more reactive than any other element. So much so that it will burn hydrocarbons at room temperature without any energy imput such as the spark required to initiate oxygen combustion under similar circumstances. Elemental fluorine is therefore a poisonous, perilous substance. Fluorine is not necessary to life, but trace amounts in the diet are effective in preventing tooth decay.PERIODIC TABLE

FM Flavin mononucleotide.

fMet N-formylmethionine.

FMN Flavin mononucleotide.

Folic Acid

folic acid (also folacin) /FOH-lik/ A B vitamin (B₉) present in such foods as liver, green vegetables, and yeast. A lack of folic acid in the diet causes anemia because it is essential in the production of erythrocytes. In the liver it is converted to dihydrofolic acid and then into tetrahydrofolate.

folium (pl folia) /FOH-lee-uhm/ A leaflike structure.

follicle-stimulating hormone (FSH) /FALL-lik-uhl/ A hormone secreted by the gonadotrope cells of the pituitary gland (i.e., a gonadotropin) in vertebrates. Its function is much broader than its name suggests. Although FSH does stimulate the production of ovarian follicles, it also plays an important role in growth, development of the sexual organs, and spermatogenesis.

fomentation /fo-men-TAY-shuhn/ The application of a hot, moist substance for the relief of pain or discomfort.

fomes /FOH-meez/ A substance that transmits infection.

foramen (pl foramina) /for-AY-muhn/ A hole, opening, or orifice in a bone (or that connects two cavities of an organ).

foramen magnum /for-AY-muhn MAHG-noom/ The large opening in the base of the skull (piercing the occipital bone) through which the spinal cord passes.

formamide /FORM-uh-mide/ A molecule (see figure right) that causes denaturation of double-stranded DNA by combining with the free NH₂ groups of adenine (which keeps A-T base pairs from forming).

forward mutation A mutation in a gene that changes it from wild type to an abnormal allele. See: back mutation.

fossil /FAH-suhl/ The remains (or traces) of an ancient organism preserved in the earth.

fossiliferous /FAH-suhl-LIF-er-uhs/ fossil-bearing, containing fossils.

fossorial /faw-SORE-ee-uhl/ Suited for digging; living in burrows.

F plasmid See: F factor.

fragmentation A mode of vegetative reproduction in which an organism breaks, or is broken, into pieces and the separate pieces go on to live as distinct individuals.

frameshift mutation A mutation that causes a reading frame shift for all codons downstream of the mutation.

fraternal twins Non-identical twins; two individuals born at the same time, but developing from two separate zygotes. See also: identical twins.

freemartin A female fraternal twins that develops male traits due to the influence in the uterus of male hormones from its male sibling when the fetal circulations are continuous.

fringillid Belonging to a family, Fringillidae, of small seed-eating finches, of which the canaries, siskins, and similar birds are members.

Fritillaria A genus of lilies much studied in the field of cytogenetics.

frontal bone The bone of the forehead.

frontoparietal Pertaining to the frontal and parietal bones.

fructose (Fru) Levulose or fruit sugar; a simple monosaccharide present in corn syrup and honey, and many fruits. Fructose is an isomer of glucose. MOLECULAR STRUCTURE

fructose-1-phosphate (F1P) The product of phosphorylation of fructose catalyzed by hepatic fructokinase. MOLECULAR STRUCTURE

fructose-6-phosphate (F6P also Neuberg ester) Fructose sugar phosphorylated on carbon 6. Fructose 6-phosphate is part of the glycolysis metabolic pathway. It is produced by isomerisation of glucose 6-phosphate. The β-D-form of F6P is abundant in cells. MOLECULAR STRUCTURE

fruit The ripe ovary of a flower.

fruit fly See: Drosophila.

FSH Follicle-stimulating hormone.

fucose (Fuc) A hexose deoxy sugar. MOLECULAR STRUCTURE

fuel cells Devices that conbine hydrogen and oxygen without combustion to generate electricity. The only by-products of the process are pure water and heat.

fungal /FUHN-guhl/ Of or pertaining to fungi.

fungus (pl fungi) /FUN-guhs, pl: FUN-ji or FUN-jee/ An organism belonging to Kingdom Fungi. Fungi are eukaryotes that form spores, as do plants, but that lack chloroplasts. The cells of most fungi grow as filamentous structures ("hyphae"), which may contain multiple nuclei, and grow from their tips. The most familiar fungi are mushrooms and toadstools, but the category also includes microorganisms such as yeasts and molds. A primary distinguishing characteristic of fungi is the presence of chitin in the cell walls, which in plants contain cellulose instead. PICTURE (Lycoperdon perlatum) | PICTURE (Amanita muscaria) | PICTURE (Laetiporus sulphureus) | PICTURE (budding yeast) | PICTURE (Penicillium)

fusion The union of formerly separate entities; in a biological context, this term often refers to a union of cells (e.g., the fusion of gametes during fertilization).