**Question:** Intracellular sorting and packing done by: (PGI Dec 2007)

**Core Concept:** Intracellular sorting and packing is a process that ensures proper transport and delivery of molecules, such as proteins, to their destinations inside the cell. This process involves various mechanisms, enzymes, and organelles to ensure accurate targeting and fusion of vesicles with their respective destinations, like lysosomes, mitochondria, or plasma membrane.

**Why the Correct Answer is Right:** Option C, the Golgi apparatus, plays a crucial role in intracellular sorting and packaging. The Golgi apparatus, also known as the Golgi complex or Golgi body, is an organelle located in eukaryotic cells. Its main function is to modify, sort, and package proteins and lipids destined for secretion, the cell membrane, or other organelles. The Golgi apparatus achieves this by:

1. Modifying proteins: The Golgi apparatus contains enzymes that modify proteins, such as adding sugar molecules (glycosylation) to prepare them for their specific functions or destinations.
2. Sorting: The Golgi apparatus sorts proteins and lipids into different vesicles based on their final destinations.
3. Packaging: Once proteins are sorted, they are packaged into vesicles for transport to their final destinations.

**Why Each Wrong Option is Incorrect:**

A. Mitochondria (Option A) are organelles involved in cellular respiration and energy production, not sorting and packaging of molecules.
B. Lysosomes (Option B) are acidic organelles responsible for cellular degradation and waste disposal, not sorting and packaging of molecules.
D. Plasma membrane (Option D) is the cell surface membrane where molecules are packaged for secretion or other destinations, but it is not involved in the sorting and packaging process itself.

**Clinical Pearl:** Understanding the role of the Golgi apparatus in intracellular sorting and packaging is essential for medical students, residents, and practicing physicians, as it helps in understanding cellular processes, protein synthesis, and the function of specific organelles in cells. Additionally, this knowledge is crucial for interpreting histopathology slides and understanding diseases associated with Golgi apparatus dysfunction, such as some lysosomal storage disorders.

**Correct Answer:** C. Golgi apparatus