Question

Which of the following statements correctly describes the distinct paths during translation for a pancreatic B-cell producing insulin and a liver cell producing the enzyme glycogen phosphorylase?

A. The pancreatic B-cell synthesizes insulin in ribosomes bound to the rough endoplasmic reticulum (RER), allowing the insulin to be secreted via vesicles, while the liver cell synthesizes glycogen phosphorylase in free ribosomes within the cytoplasm for its immediate use.

B. Both the pancreatic B-cell and liver cell synthesize their respective proteins in ribosomes bound to the rough endoplasmic reticulum (RER), allowing for direct secretion into the cytoplasm.

C. The pancreatic B-cell and liver cell both synthesize their proteins in the cytoplasm using free ribosomes; however, the pancreatic B-cell packages insulin into vesicles for secretion, whereas the liver cell immediately utilizes glycogen phosphorylase within the cytoplasm.

D. The pancreatic B-cell synthesizes insulin in the cytoplasm using free ribosomes, while the liver cell produces glycogen phosphorylase in ribosomes attached to the rough endoplasmic reticulum (RER) for direct secretion.

Answer 1

The correct description is A: Pancreatic B-cells synthesize insulin on the RER for secretion, while liver cells make glycogen phosphorylase in the cytoplasm for immediate use.

Step-by-step explanation:

The correct statement that describes the distinct paths during translation for a pancreatic B-cell producing insulin and a liver cell producing the enzyme glycogen phosphorylase is:

A. The pancreatic B-cell synthesizes insulin in ribosomes bound to the rough endoplasmic reticulum (RER), allowing the insulin to be secreted via vesicles, while the liver cell synthesizes glycogen phosphorylase in free ribosomes within the cytoplasm for its immediate use.

During the process of translation, protein synthesis begins with the formation of an initiation complex. If a protein is a secretory protein, such as insulin, the elongation directly occurs into the cisternae of the RER. The newly synthesized protein in the pancreatic B-cell then undergoes structural modifications in the RER lumen, further processed in the Golgi apparatus, and finally packaged into vesicles for secretion. In contrast, a liver cell synthesizes the enzyme glycogen phosphorylase in cytoplasmic free ribosomes because it is utilized immediately within the cytoplasm, not requiring the secretory pathway.