Intra-cellular traffic and sorting of proteins

Crack PGMEE: On a Mission to Re-imagine Medical Education
Q-1. Agranular endoplasmic reticulum takes part in synthesis of
a) Lipids
b) Proteins
c) Carbohydrates
d) Vitamins

Answer: Lipids
Explanation:
Agranular reticulum:
It is characterized by the absence of ribosomes due to which its walls are smooth.
This Agranular reticulum is most common in those cells which are concerned with steroid or lipid synthesis.

Q-2. Secretory proteins are synthesized in:
a) Cytoplasm
b) Endoplasmic reticulum
c) First in cytoplasm and then in Endoplasmic Reticulum
d) First in Endoplasmic Reticulum and then in cytoplasm

Answer: Endoplasmic reticulum
Explanation:
Secretory proteins are synthesized in rough endoplasmic reticulum
Transport route:
Rough Endoplasmic Reticulum -> Golgi body->Secretory vesicles

Q-3. The collagen triple helix structure is not found in:
a) Cytoplasm
b) Golgi apparatus
c) Lumen of endoplasmic reticulum
d) Intracellular vesicles

Answer: Cytoplasm.
Explanation:
Transport route:
Synthesis of collagen: RER-> GB-> Intra-cellular secretory vesicles-> Extra-cellular space
Important points:
Collagen is the major insoluble fibrous protein in the extracellular matrix and in connective tissue.

Q-4. Proteins are sorted by
a) Golgi bodies
b) Mitochondria
c) Ribosomes
d) Nuclear membrane

Answer: Golgi bodies
Explanation:
The Golgi apparatus is involved in glycosylation and sorting proteins.

Q-5. Intracellular sorting and packing done by
a) ER
b) Golgi apparatus
c) Ribosome
d) Cytoplasm
e) Nucleus

Answer: Golgi apparatus
Explanation:
The Golgi apparatus, or Golgi complex, functions as a factory in which proteins received from the ER are further processed and sorted for transport to their eventual destinations.
Important point:
In addition, glycolipids and sphingomyelin are synthesized within the Golgi.