Q.1 The largest membranous cellular organelle is :
l. Mitochondria
2. Peroxisomes
3. Nucleus
4. Endoplasmic reticulum
The largest membranous cellular organelle is the endoplasmic reticulum. It forms an extensive network throughout the cell, often occupying a significant portion of the cytoplasmic volume.
Option Analysis
Mitochondria are double-membraned organelles, typically rod-shaped or oval, measuring 0.5–10 μm in length. They serve as the powerhouse for ATP production but are much smaller and more discrete than the sprawling ER network.
Peroxisomes are small, single-membraned sacs around 0.1–1 μm, involved in lipid metabolism and detoxification. Their compact size excludes them from being the largest.
Nucleus, while often called the largest organelle overall (5–10 μm diameter), features a double membrane (nuclear envelope). However, among single-membraned options, it does not surpass the ER’s total expanse.
Endoplasmic reticulum (ER) is the correct answer. This single-membraned structure includes rough ER (with ribosomes) and smooth ER, forming interconnected tubules and sheets that span the entire cytoplasm, making it the largest by volume and extent.
The largest membranous cellular organelle plays a pivotal role in eukaryotic cells, handling protein and lipid synthesis. Known as the endoplasmic reticulum (ER), it dominates cytoplasmic space through its vast, interconnected network.
Structure of ER
ER consists of a single membrane forming tubules, sacs, and cisternae, continuous with the nuclear envelope. Rough ER studs with ribosomes for protein folding; smooth ER lacks them, aiding detoxification and lipid production. This dynamic system covers up to 50% of cell volume in some cells.
Why ER is Largest
Unlike compact mitochondria (powerhouses, 1–4 μm wide) or tiny peroxisomes (detoxifiers, <1 μm), ER’s sheets and tubes probe the entire cytoplasm. The nucleus, though prominent, is bounded and smaller in total membrane area.
| Organelle | Membrane Type | Typical Size | Key Role |
|---|---|---|---|
| Endoplasmic Reticulum | Single | Extensive network (cell-wide) | Protein/lipid synthesis |
| Mitochondria | Double | 0.5–10 μm | ATP production |
| Peroxisomes | Single | 0.1–1 μm | Lipid breakdown |
| Nucleus | Double | 5–10 μm diameter | Genetic control |
Exam Relevance
For competitive exams like GATE Life Sciences, questions on the largest membranous cellular organelle test organelle distinctions. ER’s single membrane and scale set it apart from double-membraned rivals.
