Essential Cell Biology 5th edition

Glossary G:5
cyclic AMP
Small intracellular signaling molecule generated from
ATP in response to hormonal stimulation of cell-surface
receptors.
cyclic-AMP-dependent protein kinase (PKA)
Enzyme that phosphorylates target proteins in response to
a rise in intracellular cyclic AMP concentration.
cyclin
Regulatory protein whose concentration rises and falls at
specific times during the eukaryotic cell cycle; cyclins help
control progression from one stage of the cell cycle to the
next by binding to cyclin-dependent protein kinases (Cdks).
cytochrome
A family of membrane-bound, colored, heme-containing
proteins that transfer electrons during cellular respiration
and photosynthesis.
cytochrome c oxidase
Protein complex that serves as the final electron carrier in
the respiratory chain; removes electrons from cytochrome c
and passes them to O 2 to produce H 2 O.
cytokinesis
Process by which the cytoplasm of a plant or animal cell
divides in two to form individual daughter cells.
cytoplasm
Contents of a cell that are contained within its plasma
membrane but, in the case of eukaryotic cells, outside the
nucleus.
cytoskeleton
System of protein filaments in the cytoplasm of a eukaryotic
cell that gives the cell shape and the capacity for directed
movement. Its most abundant components are actin
filaments, microtubules, and intermediate filaments.
cytosol
Contents of the main compartment of the cytoplasm,
excluding membrane-enclosed organelles such as
endoplasmic reticulum and mitochondria. The cell fraction
remaining after membranes, cytoskeletal components, and
other organelles have been removed.
dendrite
Short, branching structure that extends from the surface of
a nerve cell and receives signals from other neurons.
deoxyribonucleic acid (DNA)
Double-stranded polynucleotide formed from two separate
chains of covalently linked deoxyribonucleotide units.
It serves as the cell’s store of genetic information that is
transmitted from generation to generation.
depolarization
A shift in the membrane potential, making it less negative
on the inside of the cell.
desmosome
Specialized cell–cell junction, usually
formed between two epithelial cells, that
serves to connect the ropelike keratin
filaments of the adjoining cells, providing
tensile strength.
detergent
Soapy substance used to solubilize lipids and membrane
proteins.
diacylglycerol (DAG)
Small messenger molecule produced by the cleavage
of membrane inositol phospholipids in response to
extracellular signals. Helps activate protein kinase C.
dideoxy (Sanger) sequencing
The standard method of determining the nucleotide
sequence of DNA; utilizes DNA polymerase and a set of
chain-terminating nucleotides.
differentiated cell
Cell that has undergone a coordinated change in gene
expression, enabling it to perform a specialized function.
differentiation
Process by which a pluripotent cell undergoes a progressive,
coordinated change to a more specialized cell type, brought
about by large-scale changes in gene expression.
diffusion
Process by which molecules and small particles move
from one location to another by random, thermally driven
motion.
diploid
Describes a cell or organism containing two sets of
homologous chromosomes, one inherited from each
parent. (See also haploid.)
disulfide bond
Covalent cross-link formed between the sulfhydryl groups
on two cysteine side chains; often used to reinforce a
secreted protein’s structure or to join two different proteins
together.
DNA
Double-stranded polynucleotide formed from two separate
chains of covalently linked deoxyribonucleotide units.
It serves as the cell’s store of genetic information that is
transmitted from generation to generation.
DNA cloning
Production of many identical copies of a DNA sequence.
DNA library
Collection of cloned DNA molecules, representing either
an entire genome (genomic library) or copies of the mRNA
produced by a cell (cDNA library).
DNA ligase
Enzyme that seals nicks that arise in the backbone of a DNA
molecule; in the laboratory, can be used to join together two
DNA fragments.
DNA methylation
The enzymatic addition of methyl groups to cytosine bases
in DNA; this covalent modification generally turns off genes
by attracting proteins that block gene expression.
DNA polymerase
Enzyme that catalyzes the synthesis of a DNA molecule from
a DNA template using deoxyribonucleoside triphosphate
precursors.
DNA repair
Collective term for the enzymatic processes that correct
damage to DNA.
DNA replication
The process by which a copy of a DNA molecule is made.
double helix
The typical structure of a DNA
molecule in which the two
complementary polynucleotide
strands are wound around each
other with base-pairing between the strands.
dynamic instability
The rapid switching between growth and shrinkage shown
by microtubules.
dynein
Motor protein that uses the energy of ATP hydrolysis to
move toward the minus end of a microtubule. One form of
the protein is responsible for the bending of cilia.