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

G:32 Glossary
terminal differentiation The limit of cell determination when
a cell forms one of the highly specialized cell types of the adult
body.
terminally differentiated A cell at the limit of cell
determination, being one of the highly specialized cell types of
the adult body.
terminator Signal in bacterial DNA that halts transcription;
in eukaryotes, transcription terminates after cleavage and
polyadenylation of the newly synthesized RNA.
tertiary structure Complex three-dimensional form of a
folded polymer chain, especially a protein or RNA molecule.
T FH cell see follicular helper T cell
T H 1 cell A type of effector helper T cell that secretes
interferon-γ to help activate macrophages and induces B cells
to switch the class of antibody they make. (Figure 24–44)
T H 17 cell A type of effector helper T cell that secretes IL17,
which recruits neutrophils and stimulates an inflammatory
response. (Figure 24–44)
T H 2 cell A type of effector helper T cell that helps activate
B cells to produce antibodies, to undergo somatic
hypermutation, and switch the class of immunoglobulin
produced. (Figure 24–44)
thylakoid Flattened sac of membrane in a chloroplast that
contains chlorophyll and other pigments and carries out the
light-trapping reactions of photosynthesis. Stacks of thylakoids
form the grana of chloroplasts. (Figures 14–35 and 14–36)
thylakoid membrane Chloroplast membrane system
that contains the large membrane protein complexes for
photosynthesis and photophosphorylation.
thymocytes Developing T cells in the thymus.
tight junction Cell–cell junction that seals adjacent epithelial
cells together, preventing the passage of most dissolved
molecules from one side of the epithelial sheet to the other.
(Figures 19–2 and 19–21)
TIM complexes Protein translocators in the mitochondrial
inner membrane. The TIM23 complex mediates the transport of
proteins into the matrix and the insertion of some proteins into
the inner membrane; the TIM22 complex mediates the insertion
of a subgroup of proteins into the inner membrane.
(Figure 12–21)
Toll A transmembrane receptor protein. On the ventral side
of the Drosophila egg membrane, its activation controls the
distribution of Dorsal, a transcription regulator of the NFκB
family.
Toll-like receptors (TLRs) Family of pattern recognition
receptors (PRRs) on or in cells of the innate immune system.
They recognize pathogen-associated immunostimulants
(PAMPs) associated with microbes. (Figure 24–4)
TOM complex Multisubunit protein complex that transports
proteins across the mitochondrial outer membrane.
(Figure 12–21)
TOR Large, serine/threonine protein kinase that is activated
by the PI-3-kinase–Akt signaling pathway and promotes cell
growth.
totipotent Describes a cell that is able to give rise to all the
different cell types in an organism.
trans face Face on the other (far) side.
trans Golgi network (TGN) Network of interconnected
tubular and cisternal structures closely associated with the
trans face of the Golgi apparatus and the compartment from
which proteins and lipids exit the Golgi, bound for the cell
surface or another compartment.
transcellular transport Transport of solutes, such as
nutrients, across an epithelium, by means of membrane
transport proteins in the apical and basal faces of the epithelial
cells. (Figure 11–11)
transcription (DNA transcription) Copying of one strand of
DNA into a complementary RNA sequence by the enzyme RNA
polymerase. (Figures 6–1 and 6–8)
transcription regulators General name for any protein that
binds to a specific DNA sequence (known as a cis-regulatory
sequence) to influence the transcription of a gene.
transcriptional control Regulation by a cell of gene
expression by controlling when and how often a given gene is
transcribed.
transcytosis Uptake of material at one face of a cell by
endocytosis, its transfer across a cell in vesicles, and discharge
from another face by exocytosis. (Figure 13–58)
transfer RNA (tRNA) Set of small RNA molecules used in
protein synthesis as an interface (adaptor) between mRNA and
amino acids. Each type of tRNA molecule is covalently linked to
a particular amino acid. (Figure 6–50)
transferrin receptor Cell-surface receptor for transferrin (a
soluble protein that carries iron) that delivers iron to the cell
interior via receptor-mediated endocytosis and recycling of the
receptor–transferrin complex.
transformed A cell with an altered phenotype that behaves
in many ways like a cancer cell (i.e., unregulated proliferation,
anchorage-independent growth in culture).
transforming growth factor-β superfamily (TGFβ
superfamily) Large family of structurally related secreted
proteins that act as hormones and local mediators to
control a wide range of functions in animals, including
during development. It includes the TGFβ/activin and bone
morphogenetic protein (BMP) subfamilies. (Figure 15–57)
transgene The foreign or modified gene that has been added
to create a transgenic organism.
transgenic organism Plant or animal that has stably
incorporated one or more genes from another cell or organism
(through insertion, deletion, and/or replacement) and can pass
them on to successive generations. (Figures 8–53 and 8–70)
transit amplifying cell Cell derived from a stem cell
that divides a limited number of times before terminally
differentiating.
transition state Structure that forms transiently in the course
of a chemical reaction and has the highest free energy of any
reaction intermediate. Its formation is a rate-limiting step in the
reaction. (Figure 3–47)
translation (RNA translation) Process by which the
sequence of nucleotides in an mRNA molecule directs
the incorporation of amino acids into protein. Occurs on a
ribosome. (Figures 6–1 and 6–64)
translational control Regulation by a cell of gene expression
by selecting which mRNAs in the cytoplasm are translated by
ribosomes.
translocon The assembly of a translocator associated with
other membrane complexes, such as enzymes that modify the
growing polypeptide chain.