Essential Cell Biology 5th edition

Glossary G:7
a chain of enzymatic reactions reduces the activity of an
enzyme early in the pathway.
feedback regulation
Process whereby enzymes are either positively or negatively
regulated in response to the levels of metabolites that are
not their substrates.
fermentation
The breakdown of organic molecules without the
involvement of molecular oxygen. This form of oxidation
yields less energy than aerobic cell respiration.
fertilization
The fusion of two gametes—sperm and egg—to produce a
new individual organism.
fibroblast
Cell type that produces the collagen-rich extracellular matrix
in connective tissues such as skin and tendon. Proliferates
readily in wounded tissue and in tissue culture.
fibronectin
Extracellular matrix protein that helps cells attach to the
matrix by acting as a “linker” that binds to a cell-surface
integrin molecule on one end and to a matrix component,
such as collagen, on the other.
fibrous protein
A protein with an elongated, rodlike shape, such as collagen
or a keratin filament.
filopodium
Long, thin, actin-containing extension on the surface of an
animal cell. Sometimes has an exploratory function, as in a
growth cone.
flagellum
Long, whiplike structure capable of propelling a cell through
a fluid medium with its rhythmic beating. Eukaryotic flagella
are longer versions of cilia; bacterial flagella are completely
different, being smaller and simpler in construction.
fluorescence microscope
Instrument used to visualize a specimen that has been
labeled with a fluorescent dye; samples are illuminated
with a wavelength of light that excites the dye, causing it
to fluoresce.
free energy, G
Energy that can be harnessed to do work, such as driving a
chemical reaction.
free-energy change, ΔG
“Delta G”: in a chemical reaction, the difference in free
energy between reactant and product molecules. A large
negative value of ΔG indicates that the reaction has a
strong tendency to occur. (See also standard free-energy
change.)
G protein
A membrane-bound GTP-binding protein involved in
intracellular signaling; composed of three subunits, this
intermediary is usually activated by the binding of a
hormone or other ligand to a transmembrane receptor.
G-protein-coupled receptor (GPCR)
Cell-surface receptor that associates with
an intracellular trimeric GTP-binding
protein (G protein) after activation by an
extracellular ligand. These receptors are
embedded in the membrane by seven
transmembrane α helices.
G 1 cyclin
Regulatory protein that helps drive a cell through the first
gap phase of the cell cycle and toward S phase.
G 1 phase
Gap 1 phase of the eukaryotic cell cycle; falls between the
end of cytokinesis and the start of DNA synthesis.
G 1 -Cdk
Protein complex whose activity drives the cell through the
first gap phase of the cell cycle; consists of a G 1 cyclin plus
a cyclin-dependent protein kinase (Cdk).
G 1 /S cyclin
Regulatory protein that helps to launch the S phase of the
cell cycle.
G 1 /S-Cdk
Protein complex whose activity triggers entry into S phase
of the cell cycle; consists of a G 1 /S cyclin plus a cyclindependent
protein kinase (Cdk).
G 2 phase
Gap 2 phase of the eukaryotic cell cycle; falls between the
end of DNA synthesis and the beginning of mitosis.
gain-of-function mutation
Genetic change that increases the activity of a gene or
makes it active in inappropriate circumstances; such
mutations are usually dominant.
gamete
Cell type in a diploid organism that carries only one set of
chromosomes and is specialized for sexual reproduction. A
sperm or an egg; also called a germ cell.
gamete
Cell type in a diploid organism that carries only one set of
chromosomes and is specialized for sexual reproduction. A
sperm or an egg; also called a germ cell.
gap junction
In animal tissues, specialized
connection between juxtaposed
cells through which ions and small
molecules can pass from one cell to
the other.
GDP
Nucleoside diphosphate that is produced by the hydrolysis
of the terminal phosphate of GTP, a reaction that also
produces inorganic phosphate.
gene
Unit of heredity containing the instructions that dictate the
characteristics or phenotype of an organism; in molecular
terms, a segment of DNA that directs the production of a
particular protein or functional RNA molecule.
gene duplication and divergence
A process by which new genes can form; involves the
accidental generation of an additional copy of a stretch
of DNA containing one or more genes, followed by an
accumulation of mutations that over time can alter the
function or expression of either the original or its copy.
gene expression
The process by which a gene makes a product that is useful
to the cell or organism by directing the synthesis of a protein
or an RNA molecule with a characteristic activity.
gene family
A set of related genes that has arisen through a process of
gene duplication and divergence.
gene knockout
A genetically engineered animal in which a specific gene
has been inactivated.
general transcription factors
Proteins that assemble on the promoters of eukaryotic
genes near the start site of transcription and load the RNA
polymerase in the correct position.
genetic code
Set of rules by which the information contained in the
nucleotide sequence of a gene and its corresponding RNA