Cell Organelles and Cellular Processes

Question 1

Explain the process of Proteosomal Protein Degradation.

Answer 1

E1 (U activating Enzyme) activates Ubiquitin (uses ATP)
U is passed from E1 to E2 (U conjugating enzyme) forming covalent, peptide bond.
E3+U complex is bound to E3 (ligase enzyme)
E3 finds target protein and transfers U from E2 to protein.
Proteosome binds and recycles U.
Protein enters Proteosome central canal and is broken into peptides.

Question 2

Explain the process of Lysosomal Degradation of proteins.

Answer 2

Proteins are phagocytosed by lysosome
Lysosomal Enzymes are activated by acidic environment in lysosome
Enzymes (hydrolase, lipase, protease), break down substance

Question 3

What proteins are targeted by proteosomal degradation?

Answer 3

Proteins with short half life (typically Potent/toxic)
Dysfunctional proteins
Metabolic enzymes

Question 4

What proteins are targeted by lysosomal degredations?

Answer 4

Long half-life proteins
Membrane proteins (endocytosed)
Extracellular proteins (receptor mediated endocytosis)

Question 5

What proteins are synthesized by the ribosomes of the RER?

Answer 5

Secreted proteins
Plasma membrane
Lysosomes

Question 6

What proteins are synthesized by free ribosomes?

Answer 6

Proteins for mitochondria, nuclease, cytoplasm.

Peroxisomes

Question 7

What purpose does the Golgi Apparatus serve?

Answer 7

Labels proteins for destination using modifications, like glycosylation.
Proteins move from cis cisternae end -> medial -> trans, are packaged into vesicles, and sent to destination.

Question 8

Describe the process of hydrolase and mannose-6-phosphate moving from the Golgi to the destination.

Answer 8

Hydrolase travels from the RER to the Cis Cisternae of the Golgi.
Golgi glycosylates and modified hydrolase by adding mannose-6-phophate.
Receptors in trans-membrane of golgi recognize M6P, and surround hydrolase enzymes, forming vesicle.
Vesicle binds endosome