Cellbiology - Glossary and Stoyanov questions

Enzyme that joins two DNA strands together end to end.

One of the two newly made strands of DNA found at a replication fork. The leading strand is made by continuous
synthesis in the 5'-to-3' direction.

One of the two newly made strands of DNA found at a replication fork. The lagging strand is made in discontinuous
lengths that are later joined covalently.

A large family of motor proteins that use the energy of ATP hydrolysis to move along a microtubule.

Intracellular membrane-enclosed organelle containing digestive enzymes, typically those most active at the
acid pH found in these organelles.

The sum total of the chemical reactions that take place in the cells of a living organism resulting in growth,
division, energy production, excretion of waste and so on.

RNA molecule that specifies the amino acid sequence of a protein. Produced by RNA splicing (in eucaryotes)
from a larger RNA molecule made by RNA polymerase as a complementary copy of DNA. It is translated into
protein in a process catalyzed by ribosomes.

Long, stiff, cylindrical structure composed of the protein tubulin. Used by eucaryotic cells to regulate their shape and control their movements.

An extracellular signal molecule that stimulates cell proliferation.

Division of the nucleus of a eucaryotic cell, which involves condensation of the DNA into visible chromosomes.
(From Greek, mitos, a thread, referring to the threadlike appearance of the condensed chromosomes.)

Highly condensed duplicated chromosome with the two new chromosomes (also called sister chromatids) still
held together at the centromere. A chromosome during one of the stages of mitosis.

Array of microtubules and associated molecules that forms between the opposite poles of a eucaryotic
cell during mitosis; during the separation of the duplicated chromosomes, the spindle serves to move
the two chromosome sets apart.

The end of a polypeptide chain that carries a free a-amino group.

Type of motor protein that uses ATP to drive movements along actin filaments. Myosin II is a large protein that
forms the thick filaments of skeletal muscle. Smaller myosins, such as myosin I, are widely distributed and
are responsible for many actin-based movements.

Long, highly organized bundle of actin, myosin, and other proteins in the cytoplasm of muscle cells that
contracts by a sliding filament mechanism.

Small highly diffusible molecule widely used as an intracellular signal.

Net movement of water molecules across a semipermeable membrane driven by a difference in concentration of solute on either side. The membrane must be permeable to water but not to the solute molecules.

Loss of electron density from an atom.

Process in bacteria and mitochondria in which ATP formation is driven by the transfer of electrons from food
molecules to molecular oxygen. Involves the intermediate generation of a pH gradient across a membrane and
chemiosmotic coupling.

Regulatory protein that responds to the presence of DNA damage, preventing the cell from entering S phase
until the damage has been repaired.

The movement of a small molecule or ion across a membrane due to a difference in concentration or electrical charge.

The process by which particulate material is engulfed (“eaten”) by a cell.

Type of endocytosis in which soluble materials are taken up from the environment and incorporated into vesicles for digestion.

The process by which plants and some bacteria use the energy of sunlight to drive the synthesis of organic molecules
from carbon dioxide and water.

Type of lipid molecule used to make biological membranes. Generally composed of two fatty acids linked through glycerol phosphate to one of a variety of polar groups.

A covalent chemical bond in which two carbon atoms are held in ester linkage (via oxygen atoms) to the same
phosphate group; phosphodiester bonds join the adjacent nucleotides in RNA or DNA.

General term for an enzyme that catalyzes addition of subunits to a polymer. DNA polymerase, for example, makes DNA, and RNA polymerase makes RNA

Degradation of a protein by means of a protease(enzyme that breaks down proteins).

The set of successive triplets in which a string of nucleotides is translated into protein. An mRNA molecule is read in one of three possible reading frames, depending on the starting point.

One of a large family of small GTP-binding proteins (also called the monomeric GTPases) that help relay signals
from cell-surface receptors to the nucleus. Named for the Ras gene, first identified in viruses that cause rat
sarcomas.

Enzyme that catalyzes the synthesis of an RNA molecule on a DNA template from nucleoside triphosphate
precursors.

An RNA molecule possessing catalytic properties.

Particle composed of ribosomal RNAs and ribosomal proteins that associates with messenger RNA and catalyzes
the synthesis of protein.

Repeating unit of a myofibril in a muscle cell, about 2.5 mm long, composed of an array of overlapping
thick (myosin) and thin (actin) filaments.