Question

Which of the following is correct for the origin of lysosome (L)? (a) \(\mathrm{ER} \rightarrow\) Golgi bodies \(\rightarrow \mathrm{L}\) (b) Golgi bodies \(\rightarrow \mathrm{ER} \rightarrow \mathrm{L}\) (c) Nucleus \(\rightarrow\) Golgi bodies \(\rightarrow \mathrm{L}\) (d) Mitochondria \(\rightarrow \mathrm{ER} \rightarrow\) Golgi bodies \(\rightarrow \mathrm{L}\)

Short answer

The correct option for the origin of lysosomes (L) is (a) ER \rightarrow Golgi bodies \rightarrow L.

Step-by-step solution

Understanding the Function of Lysosomes

Know that lysosomes are organelles that contain digestive enzymes. They break down excess or worn-out cell parts. They may be used to destroy invading viruses and bacteria.

Knowing the Origin of Lysosomes

Understand that lysosomes are formed from the Golgi apparatus. The enzymes within are synthesized in the rough endoplasmic reticulum (ER), then transported to the Golgi apparatus, where they are processed and packaged into lysosomes.

Identifying the Correct Option

Use the knowledge from Step 2 to determine the correct pathway that leads to the formation of lysosomes. The correct pathway demonstrates that lysosomes originate from the ER, where their enzymes are synthesized, and then are sent to the Golgi apparatus for processing and finally become mature lysosomes.

Key concepts

Lysosome Function

Lysosomes are often referred to as the waste disposal system of a cell. They are small, spherical organelles filled with hydrolytic enzymes that can digest biomolecules. These enzymes are active at a lower pH, maintaining an acidic environment within lysosomes.

Lysosomes perform a variety of critical tasks, including the digestion of macromolecules from phagocytosis (ingestion of bacteria or other material by a cell), autophagy (self-degradation of damaged cell parts), and programmed cell death, known as apoptosis. By breaking down cellular debris, lysosomes also participate in recycling the cell's own organic material—a process essential for cell maintenance and renewal.

Furthermore, they are involved in several diseases termed lysosomal storage disorders, where defective lysosomal function leads to the accumulation of waste products, often resulting in severe symptoms and conditions.

Golgi Apparatus

The Golgi apparatus, also known as the Golgi complex or Golgi body, is an integral part of a cell's endomembrane system, crucial for processing and packaging proteins and lipids that have been synthesized in the endoplasmic reticulum (ER).

It consists of a series of flattened stacked pouches known as cisternae. The Golgi apparatus has a distinct polarity with two different faces: the cis face, which is near the ER and receives newly synthesized proteins, and the trans face, where these proteins are modified, sorted, and packaged into vesicles for delivery.

Function in the Formation of Lysosomes

After their synthesis in the rough ER, the hydrolytic enzymes meant for lysosomes are transported to the Golgi apparatus. Here, they undergo further modifications, such as glycosylation, and are sorted into vesicles. It's within these vesicles that lysosomal enzymes become active under acidic conditions.

Endoplasmic Reticulum

The endoplasmic reticulum (ER) is a labyrinthine organelle comprising interconnected networks of tubules and cisternae. It surrounds the nucleus and is categorized into two distinct regions: the rough endoplasmic reticulum (RER) and the smooth endoplasmic reticulum (SER).

The RER is speckled with ribosomes on its surface, where the synthesis of membrane-bound proteins and secretory proteins takes place. After their synthesis, proteins bound for lysosomes are enclosed within transport vesicles and shuttled towards the Golgi apparatus.

Role in Metabolic Processes

The SER, on the other hand, is ribosome-free and is involved in lipid synthesis, detoxification, and calcium storage. Both regions of the ER play a communal role in the synthesis and export of biomolecules. Collectively, their functions are vital not only for the production of lysosomal enzymes but also for the maintenance of overall cellular integrity and metabolism.