Essential Cell Biology 5th edition

G:4 Glossary
cholesterol
Short, rigid lipid molecule present in large amounts in the
plasma membranes of animal cells, where it makes the lipid
bilayer less flexible.
chromatin
Complex of DNA and proteins that makes up the
chromosomes in a eukaryotic cell.
chromatin-remodeling complex
Enzyme (typically multisubunit) that uses the energy of
ATP hydrolysis to alter the arrangement of nucleosomes in
eukaryotic chromosomes, changing the accessibility of the
underlying DNA to other proteins.
chromatography
Technique used to separate the individual molecules in a
complex mixture on the basis of their size, charge, or their
ability to bind to a particular chemical group. In a common
form of the technique, the mixture is run through a column
filled with a material that binds the desired molecule, and
it is then eluted from the column with a solvent gradient.
chromosome
Long, threadlike structure composed of DNA and proteins
that carries the genetic information of an organism;
becomes visible as a distinct entity when a plant or animal
cell prepares to divide.
chromosome condensation
Process by which a duplicated chromosome becomes
packed into a more compact structure prior to cell division.
cilium
Hairlike structure made of microtubules found on the
surface of many eukaryotic cells; when present in large
numbers, its rhythmic beating can drive the movement of
fluid over the cell surface, as in the epithelium of the lungs.
citric acid cycle
Series of reactions that generate large amounts of NADH
by oxidizing acetyl groups derived from food molecules
to CO 2 . In eukaryotic cells, this central metabolic pathway
takes place in the mitochondrial matrix.
classical genetic approach
Experimental techniques used to isolate the genes
responsible for an interesting phenotype.
clathrin
Protein that makes up the coat of a type of transport vesicle
that buds from either the Golgi apparatus (on the outward
secretory pathway) or from the plasma membrane (on the
inward endocytic pathway).
coated vesicle
Small membrane-enclosed sac that wears a
distinctive layer of proteins on its cytosolic
surface. It is formed by pinching-off of a
protein-coated region of cell membrane.
codon
Group of three consecutive nucleotides that specifies
a particular amino acid or that starts or stops protein
synthesis; applies to the nucleotides in an mRNA or in a
coding sequence of DNA.
coenzyme
Small molecule that binds tightly to an enzyme and helps it
to catalyze a reaction.
cohesin
Protein complex that holds sister chromatids together after
DNA has been replicated in the cell cycle.
coiled-coil
Stable, rodlike protein structure formed when two or more
α helices twist repeatedly around each other.
collagen
Triple-stranded, fibrous protein that is a major component
of the extracellular matrix and connective tissues; it is the
main protein in animal tissues, and different forms can be
found in skin, tendon, bone, cartilage, and blood vessels.
combinatorial control
Describes the way in which groups of transcription
regulators work together to regulate the expression of a
single gene.
complementary
Describes two molecular surfaces that fit together closely
and form noncovalent bonds with each other. Examples
include complementary base pairs, such as A and T, and the
two complementary strands of a DNA molecule.
complementary DNA (cDNA)
DNA molecule synthesized from an mRNA molecule and
therefore lacking the introns that are present in genomic
DNA.
complementation test
Genetic experiment that determines whether two mutations
that are associated with the same phenotype lie in the same
gene or in different genes.
condensation reaction
Chemical reaction in which a covalent bond is formed
between two molecules as water is expelled; used to build
polymers, such as proteins, polysaccharides, and nucleic
acids.
condensin
Protein complex that helps
configure duplicated chromosomes
for segregation by making them
more compact.
conformation
Precise, three-dimensional shape of a protein or other
macromolecule, based on the spatial location of its atoms
in relation to one another.
connective tissue
Tissues such as bone, tendons, and the dermis of the skin,
in which extracellular matrix makes up the bulk of the
tissue and carries the mechanical load.
conserved synteny
The preservation of gene order in the genomes of different
species.
contractile ring
Structure made of actin and myosin filaments that forms a
belt around a dividing cell, pinching it in two.
coupled reaction
Linked pair of chemical reactions in which free energy
released by one reaction serves to drive the other reaction.
covalent bond
Stable chemical link between two atoms produced by
sharing one or more pairs of electrons.
CRISPR
System for gene editing based on a bacterial enzyme that
uses a guide RNA molecule to search for and modify specific
nucleotide sequences in the genome.
crossing-over
Process whereby two homologous chromosomes break at
corresponding sites and rejoin to produce two recombined
chromosomes that have physically exchanged segments of
DNA.
cryoelectron microscopy (cryo-EM)
Technique for observing the detailed structure of a
macromolecule at very low temperatures after freezing
native structures in ice.