Question

Primary lysosomes are formed from

• A. Directly from endoplasmic reticulum or indirectly from Golgi complex
• B. Nuclear membrane
• C. Plasma membrane
• D. Mitochondrial membrane

Hint:

Remember the classic protein-targeting pathway:
Rough ER (synthesis) $\rightarrow$ Golgi (sorting and packaging) $\rightarrow$ Lysosome.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Primary lysosomes are newly formed, membrane-bound organelles that contain inactive hydrolytic enzymes.
Their production and sorting are coordinated through the endomembrane system of the cell.

Step 2: Detailed Explanation:
Lysosomal enzymes (acid hydrolases) are synthesized on the rough endoplasmic reticulum (RER) and receive a mannose-6-phosphate (M6P) tag.
They are packaged into vesicles and transported to the Golgi complex for sorting.
At the trans-Golgi network, specialized M6P receptors bind these enzymes and package them into clathrin-coated vesicles.
These transport vesicles bud off from the Golgi and mature into primary lysosomes.
Additionally, some primary lysosomes can bud directly from specialized domains of the endoplasmic reticulum.
The nuclear membrane, plasma membrane, and mitochondrial membrane are not involved in the synthesis of lysosomal hydrolases.

Step 3: Final Answer:
Primary lysosomes are generated through the endomembrane pathway, budding either directly from the endoplasmic reticulum or indirectly via the Golgi complex.