Vesicular Trafficking

Question 1

Vesicle trafficking routes

Answer 1

ER to GA, then plasmalemma (cell membrane)/lysosomes

Question 2

Trafficking to plasmalemma (constitutive secretion)

Answer 2

(All cells) Soluble proteins move to the cell surface in transport vesicles, secreted continuously

Question 3

Trafficking to plasmalemma (regulated secretion)

Answer 3

(Some cells) Soluble proteins stored in secretory vesicles, release when cell receives specific neural or hormonal signal

Question 4

Receptor mediated endocytosis

Answer 4

Substance binds w/ unique receptor protein on cell surface, receptor–substance complex taken into cell via invagination of cell membrane (endocytosis).
E.g. Transport iron and cholesterol into the cells

Question 5

Transcytosis

Answer 5

Receptor-mediated uptake of ligand at one side of cell, vesicular transport across the cell, exocytosis of vesicle contents on opposite side
Polarised cells
Transport mechanism - proteins reach GA/plasma membrane

Question 6

How are proteins transported to the correct final destination?

Answer 6

Signal sequence (amino acid sequence within protein) directs to target 
All protein synthesis begins on free ribosomes, signal sequence determines if move to rER ( proteins for cellular membranes, lysosomes and extracellular transport)
Transport to GA (modifications), then sort into lysosomes and delivered to targets according to signal sequence