BIOL 240 Exam 3: Protein Transport, Cytoskeleton, and Cell Communication

Vocabulary practice flashcards based on lecture material for BIOL 240 covering protein sorting mechanisms, cytoskeletal filaments and motors, and intracellular signal transduction.

Protein sorting (protein targeting)

The process of delivering each newly made protein to the correct compartment; directed by a sorting signal in the amino acid sequence, without which the protein remains in the cytosol.

Sorting signal (signal sequence)

A continuous stretch of amino acids (typically 15 to 60 residues long) within a protein that directs it to a specific cellular location or organelle.

Signal-recognition particle (SRP)

A cytosolic ribonucleoprotein complex consisting of RNA and proteins that binds the ER signal sequence as it emerges from the ribosome, pauses translation, and escorts the ribosome to the ER membrane.

Ran

A small monomeric GTPase that acts as a molecular switch in nuclear transport, existing primarily as Ran-GTP in the nucleus and Ran-GDP in the cytosol to create a directional gradient across the nuclear envelope.

Endosomes

Sorting stations for endocytosed material where early endosomes sort cargo so receptors recycle back to the plasma membrane and remaining material is delivered to lysosomes for degradation.

Dynamic instability

The switching of microtubule plus ends between slow growth and rapid shrinkage, governed by the presence or loss of a stabilizing GTP cap.

Axoneme (9 + 2 arrangement)

The motile core of a eukaryotic cilium or flagellum consisting of 9 outer microtubule doublets surrounding 2 central single microtubules, connected by cross-linking proteins and dynein motor arms.

Signal transduction

The conversion of an extracellular signal into an intracellular response, occurring when a signal molecule binds a receptor that relays the message through intracellular messengers to change cell behavior.

G-protein-coupled receptor (GPCR)

A cell-surface receptor composed of a single polypeptide that spans the plasma membrane 7 times and activates a trimeric G protein upon ligand binding by promoting the exchange of GDP for GTP.

Receptor tyrosine kinase (RTK)

An enzyme-coupled receptor with an intracellular tyrosine kinase domain that dimerizes upon ligand binding and cross-phosphorylates tyrosines, generating docking sites for intracellular signaling proteins.