Family
A taxonomic grouping of related, similar genera; the category below order and above genus.
Fat
A biological compound consisting of three fatty acids linked to one glycerol molecule.
Fatty acid
A long carbon chain carboxylic acid. Fatty acids vary in length and in the number and
location of double bonds; three fatty acids linked to a glycerol molecule form fat.
Feedback inhibition
A method of metabolic control in which the end-product of a metabolic pathway acts as an
inhibitor of an enzyme within that pathway.
Feedback systems
Control mechanisms whereby an increase or decrease in the level of a particular factor
inhibits or stimulates the production, utilization, or release of that factor; important in the
regulation of enzyme and hormone levels, ion concentrations, temperature, and many other
factors.
Fermentation
A catabolic process that makes a limited amount of ATP from glucose without an electron
transport chain and that produces a characteristic end-product, such as ethyl alcohol or
lactic acid.
Fertilization
The union of haploid gametes to produce a diploid zygote.
Fetal membrane
Any of the membranous structures closely associated with or surrounding a developing
vertebrate embryo, including the amnion, chorion, allantois, and yolk sac.
Fetus
An unborn or unhatched vertebrate that has passed through the earliest developmental
stages; a developing human from about the second month of gestation until birth.
Fiber
A lignified cell type that reinforces the xylem of angiosperms and functions in mechanical
support; a slender, tapered sclerenchyma cell that usually occurs in bundles.
Fibril
Any minute, threadlike structure within a cell.
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