Essential Cell Biology 5th edition

Glossary G:3
Ca 2+ /calmodulin-dependent protein kinase
(CaM-kinase)
Enzyme that phosphorylates target proteins in response to
an increase in Ca 2+ ion concentration through its interaction
with the Ca 2+ -binding protein calmodulin.
cadherin
A member of a family of Ca 2+ -dependent proteins that
mediates the attachment of one cell to another in animal
tissues.
calmodulin
Small Ca 2+ -binding protein that modifies the activity of
many target proteins in response to changes in Ca 2+
concentration.
cancer
Disease caused by abnormal and uncontrolled cell
proliferation, followed by invasion and colonization of body
sites normally reserved for other cells.
carbon fixation
Process by which green plants and other photosynthetic
organisms incorporate carbon atoms from atmospheric
carbon dioxide into sugars. The second stage of
photosynthesis.
caspase
One of a family of proteases that, when activated, mediates
the destruction of the cell by apoptosis.
catabolism
Set of enzyme-catalyzed reactions by which complex
molecules are degraded to simpler ones with release of
energy; intermediates in these reactions are sometimes
called catabolites.
catalyst
Substance that accelerates a chemical reaction by lowering
its activation energy; enzymes perform this role in cells.
Cdk (cyclin-dependent protein kinase)
Enzyme that, when complexed with a regulatory cyclin
protein, can trigger various events in the cell-division cycle
by phosphorylating specific target proteins.
Cdk inhibitor protein
Regulatory protein that blocks the assembly or activity
of cyclin–Cdk complexes, delaying progression primarily
through the G 1 and S phases of the cell cycle.
cDNA library
Collection of DNA fragments synthesized using all of the
mRNAs present in a particular type of cell as a template.
cell
The basic unit from which a living organism is made; an
aqueous solution of chemicals, enclosed by a membrane,
that has an ability to self-replicate.
cell cortex
Specialized layer of cytoplasm on the inner face of the
plasma membrane. In animal cells, it is rich in actin
filaments that govern cell shape and drive cell movement.
cell cycle
The orderly sequence of events by which
a cell duplicates its contents and divides
into two.
cell junction
Specialized region of connection between two cells or
between a cell and the extracellular matrix.
cell memory
The ability of differentiated cells and their descendants to
maintain their identity.
cell respiration
Process by which cells harvest the energy stored in food
G2
S
M
G1
molecules; usually accompanied by the uptake of O 2 and
the release of CO 2 .
cell signaling
The molecular mechanisms by which cells detect and
respond to external stimuli and send messages to other
cells.
cell wall
Mechanically strong fibrous layer deposited outside the
plasma membrane of some cells. Prominent in most plants,
bacteria, algae, and fungi, but not present in most animal
cells.
cell-cycle control system
Network of regulatory proteins that govern the orderly
progression of a eukaryotic cell through the stages of cell
division.
cellulose microfibril
Long, thin polysaccharide fiber that helps strengthen plant
cell walls.
centriole
Cylindrical array of microtubules usually found in pairs at
the center of a centrosome in animal cells. Also found at the
base of cilia and flagella, where they are called basal bodies.
centromere
Specialized DNA sequence that
allows duplicated chromosomes to
be separated during M phase; can
be seen as the constricted region of
a mitotic chromosome.
centrosome
Microtubule-organizing center that sits near the nucleus in
an animal cell; during the cell cycle, this structure duplicates
to form the two poles of the mitotic spindle.
centrosome cycle
Process by which the centrosome duplicates (during
interphase) and the two new centrosomes separate (at
the beginning of mitosis) to form the poles of the mitotic
spindle.
channel
A protein that forms a hydrophilic pore
across a membrane, through which
selected small molecules or ions can
passively diffuse.
chemical bond
A sharing or transfer of electrons that holds two atoms
together. (See also covalent bond and noncovalent
bond.)
chemical group
A combination of atoms, such as a hydroxyl group (–OH) or
an amino group (–NH 2 ), with distinct chemical and physical
properties that influence the behavior of the molecule in
which it resides.
chemiosmotic coupling
Mechanism that uses the energy stored in a transmembrane
proton gradient to drive an energy-requiring process, such
as the synthesis of ATP by ATP synthase or the transport of
a molecule across a membrane.
chiasma (plural chiasmata)
X-shaped connection between paired homologous
chromosomes during meiosis; represents a site of crossingover
between two non-sister chromatids.
chlorophyll
Light-absorbing green pigment that plays a central part in
photosynthesis.
chloroplast
Specialized organelle in algae and plants that contains
chlorophyll and serves as the site for photosynthesis.