Essential Cell Biology 5th edition

G:18 Glossary
tubulin
Protein from which microtubules are made.
tumor suppressor gene
A gene that in a normal tissue cell inhibits cancerous
behavior. Loss or inactivation of both copies of such a gene
from a diploid cell can cause it to behave as a cancer cell.
turnover number
The maximum number of substrate molecules that an
enzyme can convert into product per second.
tyrosine kinase
Enzyme that phosphorylates target proteins on tyrosines.
unfolded protein response (UPR)
Molecular program triggered by the accumulation of
misfolded proteins in the endoplasmic reticulum. Allows
cells to expand the endoplasmic reticulum and produce
more of the molecular machinery needed to restore proper
protein folding and processing.
unsaturated
Describes an organic molecule that contains one or more
double or triple bonds between its carbon atoms.
van der Waals attraction
Weak noncovalent interaction, due to fluctuating electrical
charges, that comes into play between two atoms within a
short distance of each other.
vesicular transport
Movement of material between organelles in the eukaryotic
cell via membrane-enclosed vesicles.
virus
Particle consisting of nucleic acid (RNA
or DNA) enclosed in a protein coat and
capable of replicating within a host cell
and spreading from cell to cell.
V max
The maximum rate of an enzymatic reaction, reached when
the active sites of all of the enzyme molecules in a sample
are fully occupied by substrate.
voltage-gated channel
Channel protein that permits the passage of selected ions,
such as Na + , across a membrane in response to changes
in the membrane potential. Found primarily in electrically
excitable cells such as nerve and muscle cells.
voltage-gated Na + channel
Protein in the plasma membrane of electrically excitable
cells that opens in response to membrane depolarization,
allowing Na + to enter the cell. It is responsible for action
potentials in these cells.
Wnt protein
Member of a family of extracellular signal molecules that
regulates cell proliferation and migration during embryonic
development and that maintains stem cells in a proliferative
state.
x-ray crystallography
Technique used to determine the three-dimensional
structure of a protein molecule by analyzing the diffraction
pattern produced when a beam of x-rays is passed through
an ordered array of the protein.
zygote
Diploid cell produced by fusion of a male and a female
gamete. A fertilized egg.