Intracellular Transport Vocab

Here is a list of essential vocabulary and definitions from the sources to help you prepare for your exam:

Cellular Compartments & Organelles

  • Cytosol: The main compartment of the cell (excluding membrane-enclosed organelles) where metabolic pathways and protein synthesis occur.

  • Nucleus: The site that contains the genome and is responsible for DNA and RNA synthesis.

  • Endoplasmic Reticulum (ER): The site of protein and lipid synthesis, and the entry point for proteins destined for the ER, Golgi, endosomes, lysosomes, and the cell surface.

  • Golgi apparatus: The compartment responsible for the modification and packaging of lipids and proteins.

  • Lysosomes: Organelles responsible for intracellular degradation.

  • Endosomes: Compartments involved in the sorting of endocytosed materials.

  • Mitochondria: Organelles that perform ATP synthesis via oxidative phosphorylation.

  • Chloroplasts: Organelles that handle ATP synthesis and carbon fixation through photosynthesis.

  • Peroxisomes: Organelles responsible for the oxidation of toxic molecules.

  • Endomembrane System: A system formed by the invagination of the plasma membrane that includes the ER, Golgi apparatus, peroxisomes, endosomes, and lysosomes.

Protein Sorting & Nuclear Transport

  • Signal Sequence: A sequence of amino acids (like KDEL for ER retention) that directs a protein to its specific destination.

  • Nuclear Pore Complex: A large, water-filled channel in the nuclear envelope that allows free diffusion of small molecules and active transport of specific macromolecules.

  • Nuclear Localization Signal: A specific signal that directs a newly synthesized protein from the cytosol into the nucleus.

  • Nuclear Import Receptors: Cytosolic proteins that recognize the nuclear localization signal and guide the protein to the nuclear pore.

  • Ran-GAP (GTPase Activating Protein): A cytosolic accessory protein that triggers GTP hydrolysis in the Ran GTPase cycle, which drives nuclear transport.

  • Ran-GEF (Guanine Nucleotide Exchange Factor): A nuclear-localized accessory protein that promotes the exchange of GDP for GTP in the nucleus during nuclear transport.

Membrane Transport (ER)

  • Signal Recognition Particle (SRP): A particle that binds to the ribosome and the ER signal sequence as the protein is being synthesized, slowing down translation.

  • Protein Translocator: A channel in the ER membrane through which the newly synthesized protein is threaded.

  • Signal Peptidase: An enzyme that cleaves the ER signal sequence off of a soluble protein once it has crossed into the ER lumen.

  • Stop-Transfer Sequence: A hydrophobic sequence that halts translocation, causing a single-pass transmembrane protein to be retained in the lipid bilayer.

  • Start-Transfer Sequence: An internal hydrophobic signal sequence that anchors a multiple-pass transmembrane protein in the membrane.

Vesicular Transport

  • Transport Vesicles: Vesicles that carry soluble proteins and membrane components between the endomembrane system and the plasma membrane.

  • Coated Vesicles: Vesicles that bud from membranes with a distinctive protein coat on their cytosolic surface, which helps shape the membrane and capture cargo.

  • Adaptins: Proteins that capture specific cargo molecules and secure the clathrin protein coat to the vesicle membrane.

  • Dynamin: A GTP-binding protein that assembles around the neck of a budding vesicle to pinch it off from the membrane.

  • v-SNAREs and t-SNAREs: Complementary receptors found on the transport vesicle (v-SNARE) and the target membrane (t-SNARE) that pair together, forcing the lipid bilayers into close proximity so they can fuse.