JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD Pharm. D I Year REMEDIAL BIOLOGY Previous Question Paper (October/November - 2019 - R08)

Membrane-bound organelles are specialized structures within plant cells that perform distinct physiological functions. The key organelles are described below:

1. Nucleus: The control center of the cell, enclosed by a double-membrane nuclear envelope. It contains genetic material (DNA) organized into chromatin and is responsible for regulating gene expression, DNA replication, and ribosome synthesis within the nucleolus.

2. Mitochondria: Known as the powerhouse of the cell, these organelles possess a double membrane, with the inner membrane folded into cristae. They are the primary sites of aerobic respiration, where ATP is generated through the Krebs cycle and oxidative phosphorylation.

3. Chloroplasts: Unique to plants, these contain chlorophyll and are surrounded by a double membrane. They consist of thylakoid stacks (grana) embedded in stroma. Their primary function is photosynthesis, converting light energy into chemical energy stored as glucose.

4. Endoplasmic Reticulum (ER): A network of membranous tubules and sacs. The Rough ER, studded with ribosomes, is involved in protein synthesis and folding. The Smooth ER lacks ribosomes and is primarily responsible for lipid synthesis, detoxification, and calcium storage.

5. Golgi Apparatus: Composed of flattened sacs called cisternae, this organelle acts as the cell's packaging and distribution center. It modifies, sorts, and packages proteins and lipids received from the ER into vesicles for secretion or delivery to other organelles.

6. Vacuole: A large, membrane-bound sac known as the tonoplast. In mature plant cells, the central vacuole occupies most of the cell volume. It maintains turgor pressure, stores nutrients, waste products, and pigments, and contributes to cell growth.

7. Peroxisomes: Small, single-membrane vesicles containing oxidative enzymes. They are crucial for photorespiration, breaking down fatty acids, and neutralizing hydrogen peroxide produced during metabolic processes.