Intracellular Vesicular Traffic

Question 1

Membrane enclosed compartments filled with hydrolytic enzymes

Answer 1

lysosomes

Question 2

Lysosomes are derived from

Answer 2

Heterogeneous-derived from late endosomes

Question 3

What are lysosomes important for

Answer 3

intracellular digestion of macromolecules

Question 4

There are about ___ types of enzymes in lysosomes which are:

Answer 4

• 40
• proteases, nucleases, glycosidases, lipases, phospholipases, phosphatases, and sulfatases

Question 5

Lysosomes require ______ enviroment and _____ for optimal activation

Answer 5

acidic enivironment and proteolytic cleavage

Question 6

_____ pumps H+ into lysosomes to maintian the acidic pH and to dirve transport of small metabolites

Answer 6

Vacuolar ATPase

Question 7

The endolysome gets its vesicles

Answer 7

• Plasma membrane
• Trans Golgi network

Question 8

early endosome goes throuh _____ before becoming late endosome

Answer 8

microtubule mediated transport

Question 9

Mode for lysomosome maturation: late endosomes fuse with ______ or _______. Endolysosomes eventually mature into lysosomes as hydrolases complete the digestion of their contents, which can include intralumenal vesicles.

Answer 9

preexisting lysosomes, preexisting endolysosomes

Question 10

what are the multiple pathways that deliver materials to lysosomes

Answer 10

• Endocytosis
• Phagocytosis
• Macropinocytosis
• Autophagy

Question 11

model of autophagy

Answer 11

• activation of a signaling pathway initiates a nucleation event in the cytoplasm. A crescent of autophagosomal membrane grows by fusion of vesicles of unknown origin and eventually fuses to form a double-membrane-enclosed autophagosome, which sequesters a portion of the cytoplasm. The autophagosome then fuses with lysosomes containing acid hydrolases that digest its content. During the formation of the autophagosome membrane, a ubiquitin-like protein becomes activated y covalent attachment of a phosphatidylethanolamine lipid anchor. These proteins then mediate vesicle tethering and fusion, leading to the formation of a crescent-shaped membrnae structure that assembles around its target.

Question 12

A ______ receptor sorts lysosomal hydrolases in the Trans Golgi Network

Answer 12

Mannose 6-Phosphate

Question 16

Lysosomal hyrolases have a sorting signal _____ attached to them in the Cis-Golgi Network

Answer 16

Mannose-6-Phosphate (M6P)

Question 17

M6P receptors in ______ recognize the sugar. Receptors bind to hydrolases and adaptor proteins to package them into ______ that bud from the TGN and deliver their contents to early endosomes

Answer 17

Trans Golgi Network, clathrin coated vesicles

Question 20

The Transport of newly synthesized lysomal hydrolases to endosomes

Answer 20

The sequential action of two enzymes in the cis and trans Golgi network adds mannose 6-phosphate (M6P) groups to the precursors of lysosomal enzymes. The M6P-tagged hyrolases then segregate from all other types of proteins in the TGN because adaptor proteins in the clathrin coat bind the M6P-modified lysosomal hydrolases. The clathrin-coated vesicles bud off from the TGN, shed their coat, and fuse with early endosomes. At the lower pH of the endosome, the hydrolases dissociate from the M6P receptors, and the empty receptors are retrieved in retromer-coated vesicles to the TGN for further rounds of trnasport. In the endosomes, the phsosphate is removed form the M6P attached to the hydrolases, which may further ensure that the hydrolases do not return to the TGN with the receptor