[W2] Intracellular trafficking Flashcards
(30 cards)
What is compartmentalisation in eukaryotic cells?
Division of the cell into membrane-bound organelles, each performing specific functions.
What are the advantages of compartmentalisation?
Increased efficiency, separation of incompatible reactions, and spatial control of processes.
What problems can arise from compartmentalisation?
The need for accurate protein targeting, transport mechanisms, and membrane integrity.
What are membraneless organelles and how do they form?
Cellular compartments without membranes formed via liquid–liquid phase separation.
Give examples of membraneless organelles.
Nucleolus, P bodies, and nuclear speckles.
What are protein targeting sequences?
Short peptide motifs that direct proteins to specific cellular destinations.
Name five types of targeting sequences.
Signal peptides, transmembrane domains, NLS, NES, organelle-specific uptake sequences.
What is the function of a nuclear localisation sequence (NLS)?
Directs proteins into the nucleus via importins and nuclear pores.
What is the function of a nuclear export sequence (NES)?
Facilitates protein export from the nucleus via exportins.
What organelle uses peroxisomal targeting signals?
Peroxisomes.
What do peroxisomes do?
Use molecular oxygen to oxidize substrates, forming H₂O₂, which is broken down by catalase.
Where are most mitochondrial and chloroplast proteins encoded?
In the nucleus.
How are mitochondrial proteins imported?
Via N-terminal pre-sequences and chaperones (e.g. Hsc70) keeping them unfolded.
What is the role of the signal recognition particle (SRP)?
Guides ribosome-nascent chain complex to the ER membrane for translocation.
What is a translocon?
A protein-conducting channel in the ER membrane that imports proteins.
How are membrane proteins inserted into the membrane?
Through internal signal sequences and start/stop transfer sequences during translation.
What was the 2013 Nobel Prize in Physiology or Medicine awarded for?
Discoveries in vesicle trafficking machinery by Schekman, Rothman, and Südhof.
What did Randy Schekman discover?
Genes that control vesicle traffic in yeast.
What did James Rothman discover?
SNARE proteins that mediate vesicle fusion.
What did Thomas Südhof discover?
How signals regulate the timing of vesicle cargo release.
How were yeast mutants used to study secretion?
Temperature-sensitive mutants revealed genes essential for vesicle transport.
What is the function of the Golgi apparatus?
Processes and sorts proteins from the ER for delivery to their final destinations.
What is the KDEL retrieval pathway?
A system that returns escaped ER proteins from the Golgi back to the ER.
What are coated vesicles?
Vesicles covered in proteins like clathrin or COPI/COPII that help in vesicle formation.
