Biology Dictionary F

Meanings of biological terminology

Biology images


Words Prefixes Suffixes Roots
a | b | c | d | e | f | g | h | i-k | l

m | n | o | p-q | r | s | t |  u-z 


Like this dictionary? Then please tell your friends!

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.

F₁ generation The first filial generation, the generation produced by an initial cross between 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 Fn generation is produced by interbreeding of individuals belonging to the Fn-1 generation. MORE INFORMATION

F6P Fructose-6-phosphate.

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

Online Biology Dictionary (FAC-)

face The portion of the head extending from the forehead to the chin and anterior to, but not including, the ears. FACIAL MUSCLES IN LATERAL VIEW

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 /FASH-ee-oh-SIR-vick-əl/ Pertaining to the face and neck.

faciolingual /FASH-ee-oh-LING-yoo-əl/ Pertaining to the face and tongue.

facioplasty /FASH-ee-oh-PLAST-ee/ Facial plastic surgery.

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

facultative anaerobe /AN-ə-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 /fə-LOPE-ee-ən/ Ducts by which ova pass from the ovaries to the uterus.

family /FAM-lee/ 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 pharynxfaucial /FAW-see-əl/

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

faucitis /fə-SIGHT-əs/ Inflammation of the fauces.

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

Fayum Formation /FAY-əm/ A geological formation in northeastern Egypt. It is composed primarily of Oligocene strata. MORE INFORMATION

Online Biology Dictionary (FBP)

FBP Fructose-1,6-bisphosphate.

FBPase Fructose bisphosphatase.

Fd Ferredoxin.

Online Biology Dictionary (FEBRI-)

febricity /fə-BRISS-ə-dee, fee-/ State of being feverish.

febrifuge /FEB-rə-fyooj/ A fever-reducing agent.

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

febris /FEB-brəs, FAY-brəs/ Fever.

fecal (Brit:faecal) /FEE-kəl/ Of or pertaining to feces.

fecal coliform bacteria (often shortened to: fecal coliforms) /FEE-kəl KOLE-ə-form/ Coliform bacteria originating in feces (such as Escherichia). Some coliform bacteria (e.g. those of the genera Enterobacter, Klebsiella, and Citrobacter) are not of fecal origin. Coliform bacteria are rod-shaped, gram-negative, non-spore forming bacteria that ferment lactose with the production of acid and gas when incubated at 35-37°C. They occur widely in the environment in water, soil and vegetation. Fecal coliforms are always present in the feces of warmblooded animals. Although bacteria of this kind are not ordinarily the cause of serious illness, they are used as an indicator of the presence of other pathogenic organisms of fecal origin that are not as easily detected.

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

fecula (pl feculae) /FEK-yə-lə/ 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.

felid /FEEL-əd/ (1) member of the family Felidae; a cat; (2) pertaining to the family Felidae.

Felidae /FEEL-ə-DEE/ The mammalian family that contains the cats.

Online Biology Dictionary (FEMORO-)

femorotibial /fə-MORE-oh-TIB-ee-əl/ Pertaining to the femur and the tibia.

femtoliter (fL) /FEM-tə-LEET-er/ One million-billionth (10⁻¹⁵) of a liter.

femtosecond (fs) /FEM-tə-SECK-und/ One million-billionth (10⁻¹⁵) of a second.

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

ferment /fur-MENT/ To undergo, or cause to undergo, fermentation.

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 /fert-əl-eye-ZAY-shən/ The union of a male and a female gamete to form a zygote.

fertilize /FERT-əl-eyes/ (1) in a male gamete: to join with a female gamete in fertilization; (2) in a male organism: to place male gametes within a female or on eggs.

Online Biology Dictionary (FET-)

fetal /FEET-əl/ Of or pertaining to the fetus.

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

fetus (Brit: foetus) /FEET-əs/ A developing mammal, or other viviparous vertebrate, after the embryonic stage and before birth. VIDEO OF HUMAN EMBRYONIC AND FETAL DEVELOPMENT

fever /FEEV-ur/ Elevated body temperature; specifically, the medical definition of fever in a human being is any temperature at or above 100.4 degrees (38C).

feverish /FEEV-ur-ish/ Having a fever.

FH Familial hypercholesterolemia.

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

Online Biology Dictionary (FIBUL-)

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

fibulocalcaneal /FIB-yə-loe-kal-KANE-ee-əl/ Pertaining to the fibula and calcaneus.

Online Biology Dictionary (FIL-)

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

filial generation /FILL-ee-əl/ 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


where the subscripts indicate the number of residues present. 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.

fistula /FIS-chə-lə/ n. An abnormal tube-shaped passage or structure.

fl Femtoliter.

flabellum /flə-BELL-əm/ n. A fan-shaped part.

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

Online Biology Dictionary (FLAGELL-)

flagellin /flə-JEHL-ən/ The main protein component of bacterial flagella.

flagellum (pl flagella) /flə-JEHL-əm/ (1) threadlike motile process serving in the locomotion of a microorganism (see: undulipodium) PICTURE; (2) any filiform process of an animal.

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

flatworm A flat worm belonging to the phylum Platyhelminthes.

Online Biology Dictionary (FLAV-)

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.

Online Biology Dictionary (FLO-)

flora /FLORE-ə/ (1) the plant life, as opposed to animal life (fauna), of an era, geographic region, or biome; (2) gut flora: microorganisms living in the digestive tract. See biota.

flow cytometry /sigh-TOM-ə-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.

flower A reproductive shoot of an angiosperm. FLOWER PARTS

flower, perfect A perfect flower has both pistils and stamens.

flower, pistillate A pistillate flower has pistils, but not stamens.

flower, staminate A staminate flower has stamens, but not pistils.

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 /flə-RESS-əns, floh-/ The emission of electromagnetic radiation (usually visible light) by a substance, that has absorbed radiation of some other wavelength.

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.

fluorescent /flə-RESS-ənt, floh-/ Exhibiting fluorescence.

fluorine (F) /FLOO-ə-reen 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 input, 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.

Online Biology Dictionary (FOL-)
folic acid
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-əm/ A leaflike structure.

folivorous /foh-LIV-ver-əs/ Leaf-eating.

follicle /FALL-ə-kəl/ Any small, bulbous group of cells forming a cavity.

follicle-stimulating hormone (FSH) /FALL-lik-əl/ 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-shən/ The application of a hot, moist substance for the relief of pain or discomfort.

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

fontanel or fontanelle /FONT-ə-nel/ The large gap in the bony structure of the skull found at the peak of the skull in fetal and newborn infants.

Online Biology Dictionary (FOR-)

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

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

formamide structure

formamide /FORM-ə-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.

Online Biology Dictionary (FOSSIL)

fossil /FAW-səl/ (1) n. The remains, or traces, of an ancient organism preserved in the earth; (2) adj. Being, or pertaining to, such remains or traces.

fossiliferous /faw-səl-LIF-er-əs/ fossil-bearing, containing fossils.

fossorial /faw-SORE-ee-əl/ 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 twin that develops male traits due to the influence in the uterus of male hormones from its male sibling when the fetal circulations are continuous (the term is usually used in connection with cattle, although the condition occurs, too, in sheep, goats and pigs).

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 because of their very large chromosomes. Lilies of this genus have the highest C-values among plants, ranging up to F. assyriaca, in which a haploid nucleus contains 127.4 pg of DNA.

Online Biology Dictionary (FRONT-)

frontal /FRUN-təl/ (1) of or pertaining to the front; (2) lying at the front.

frontal bone The bone underlying the forehead.

frontal lobe One of the two anterior lobes of the brain that underlie the forehead. Taken together, the two frontal lobes are the frontal region.

frontoparietal /FRUNT-oh-pə-RYE-ə-təl/ Pertaining to the frontal and parietal bones.

Online Biology Dictionary (FRUCT-)

fructose (Fru) (also 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

frugivorous /froo-GIV-er-əs/ Fruit-eating.

fruit The ripe ovary of a flower.

fruit fly See: Drosophila.

fruit sugar An alternative name for fructose.

fs Femtosecond;

FSH Follicle-stimulating hormone.

fucose (Fuc) A hexose deoxy sugar. MOLECULAR STRUCTURE

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

functional group Organic chemistry: any of various specific groups of atoms, as the acyl group or hydroxyl group, that engage in similar chemical reactions even when they are components of distinct molecules.

Online Biology Dictionary (FUNG-)

fungal /FUN-gəl/ Of or pertaining to fungi.

fungus (pl fungi) /FUN-gəs, pl: FUN-jigh, -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).

Words Prefixes Suffixes Roots
a | b | c | d | e | f | g | h | i-k | l

m | n | o | p-q | r | s | t |  u-z 

Search the dictionary >>

Most shared on

Human Origins: Are we hybrids?

On the Origins of New Forms of Life

Mammalian Hybrids

Cat-rabbit Hybrids: Fact or fiction?

Famous Biologists

Dog-cow Hybrids

Prothero: A Rebuttal

Branches of Biology

Dog-fox Hybrids