Molecular Biology of the Cell by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morgan, Martin Raff, Keith Roberts, Peter Walter by by Bruce Alberts, Alexander Johnson, Julian Lewis, David Morg

Glossary G:9
electrons from cytochrome c and generates water using
molecular oxygen as an electron acceptor. (Figure 14–18)
cytochrome c reductase Second of the three electrondriven
proton pumps in the respiratory chain. Accepts electrons
from ubiquinone and passes them to cytochrome c.
(Figure 14–18)
cytokine Extracellular signal protein or peptide that acts as a
local mediator in cell–cell communication.
cytokine receptor Cell-surface receptor that binds a specific
cytokine or hormone and acts through the JAK–STAT signaling
pathway. (Figure 15–56)
cytokinesis Division of the cytoplasm of a plant or animal cell
into two, as distinct from the associated division of its nucleus
(which is mitosis). Part of M phase. (Panel 17–1, pp. 980–981)
cytoplasm Contents of a cell that are contained within its
plasma membrane but, in the case of eukaryotic cells, outside
the nucleus.
cytoplasmic tyrosine kinase Enzyme activated by certain
cell-surface receptors (tyrosine-kinase-associated receptors)
that transmits the receptor signal onward by phosphorylating
target cytoplasmic proteins on tyrosine side chains.
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-bounded organelles such as endoplasmic
reticulum and mitochondria.
cytotoxic T cell (T C cell) Type of T cell responsible for killing
host cells infected with a virus or another type of intracellular
pathogen. (Figure 24–42)
dark-field microscopy Type of light microscopy in which
oblique rays of light focused on the specimen do not enter the
objective lens, but light that is scattered by components in the
living cell can be collected to produce a bright image on a dark
background. (Figure 9–7)
death receptor Transmembrane receptor protein that
can signal the cell to undergo apoptosis when it binds its
extracellular ligand. (Figure 18–5)
death-inducing signaling complex (DISC) Activation
complex in which initiator caspases interact and are activated
following binding of extracellular ligands to cell-surface death
receptors in the extrinsic pathway of apoptosis.
deep RNA sequencing see RNA-seq
default pathway The transport pathway of proteins directly
to the cell surface via the nonselective constitutive secretory
pathway, entry into which does not require a particular signal.
defensin Positively charged, amphipathic, antimicrobial
peptide—secreted by epithelial cells—that binds to and
disrupts the membranes of many pathogens.
delayed K + channel Neuronal voltage-gated K + channel
that opens following membrane depolarization but during the
falling phase of an action potential due to slower activation
kinetics than Na + channels; opening permits K + efflux, driving
the membrane potential back toward its original negative value,
ready to transmit a second impulse.
Delta Single-pass transmembrane signal protein displayed
on the surface of cells that binds to the Notch receptor protein
on a neighboring cell, activating a contact-dependent signaling
mechanism.
dendrite Extension of a nerve cell, often elaborately
branched, that receives stimuli from other nerve cells.
dendritic cell The most potent type of antigen-presenting
cell, which takes up antigen and processes it for presentation
to T cells. It is required for activating naïve T cells.
(Figure 24–11)
deoxyribonucleic acid (DNA) Polynucleotide formed
from covalently linked deoxyribonucleotide units. The store
of hereditary information within a cell and the carrier of this
information from generation to generation. (Figure 4–3 and
Panel 2–6, pp. 100–101)
depolarization Deviation in the electric potential across the
plasma membrane towards a positive value. A depolarized cell
has a potential that is positive outside and negative inside.
desensitization see adaptation
desmosome Anchoring cell–cell junction, usually formed
between two epithelial cells. Characterized by dense plaques
of protein into which intermediate filaments in the two adjoining
cells insert. (Figure 19–2)
detergent Small amphiphilic molecule, more soluble in water
than lipids, that disrupts hydrophobic associations and destroys
the lipid bilayer thereby solubilizing membrane proteins.
D gene segment A short DNA sequence that encodes a part
of the variable region of an immunoglobulin heavy chain or the
β chain of a T cell receptor (TCR).
diacylglycerol (DAG) Lipid produced by the cleavage of
inositol phospholipids in response to extracellular signals.
Composed of two fatty acid chains linked to glycerol, it serves
as a small signaling molecule to help activate protein kinase C
(PKC). (Figure 15–28)
dideoxy sequencing The standard enzymatic method of
DNA sequencing. (Panel 8–1, p. 478)
differential-interference-contrast microscope Type of
light microscope that exploits the interference effects that occur
when light passes through parts of a cell of different refractive
indices. Used to view unstained living cells.
differentiation Process by which a cell undergoes a change
to an overtly specialized cell type.
diffusion The net drift of molecules through space due to
random thermal movements.
Dishevelled Scaffold protein recruited to the Frizzled family of
cell-surface receptors upon their activation by Wnt binding that
helps relay the signal to other signaling molecules.
DNA cloning (1) The act of making many identical copies
(typically billions) of a DNA molecule—the amplification of a
particular DNA sequence. (2) Also, the isolation of a particular
stretch of DNA (often a particular gene) from the rest of the
cell’s genome.
DNA helicase Enzyme that is involved in opening the DNA
helix into its single strands for DNA replication.
DNA library Collection of cloned DNA molecules,
representing either an entire genome (genomic library) or
complementary DNA copies of the mRNA produced by a cell
(cDNA library).
DNA ligase Enzyme that joins the ends of two strands of
DNA together with a covalent bond to make a continuous DNA
strand.
DNA methylation Addition of methyl groups to DNA.