Protein Transport

Question 1

What are the different possible destinations of proteins whose synthesis is completed on free ribosomes?

Answer 1

remain in the cytosol/cytoplasm
nucleus
mitochondria
chloroplasts
membranes
cytoskeleton

Question 2

What are the different possible destinations of proteins that enter the endomembrane system?

Answer 2

ER (rough and smooth)
golgi apparatus
lysosomes
secretion (outside the cell)
plasma membrane
intracellular organelles

Question 3

How does a protein enter the endomembrane system? What is the role of the enzyme signal peptidase?

Answer 3

protein synthesis starts on free ribosome
SRP binds to signal peptide
SRP binds to translocation complex in ER
SRP leaves - polypeptide chain grows
signal peptide cleaved by signal peptidase
polypeptide released into ER lumen

Question 4

What tells the protein where to go?

Answer 4

amino acid code