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

The cell is the fundamental structural and functional unit of all living organisms, acting as a complex biochemical factory. Its biochemical organization is defined by compartmentalization, which allows for the simultaneous occurrence of diverse metabolic processes.

Biochemical Organization of the Cell:

1. Plasma Membrane: A selectively permeable lipid bilayer containing integral and peripheral proteins. It regulates the transport of ions, nutrients, and waste, and serves as a site for signal transduction.
2. Cytoplasm and Cytosol: The aqueous phase containing dissolved enzymes, metabolites, and electrolytes. It is the site of glycolysis, fatty acid synthesis, and protein synthesis via ribosomes.
3. Nucleus: The repository of genetic material (DNA). It controls cellular activities through gene expression, replication, and transcription.
4. Mitochondria: Known as the powerhouse of the cell, these organelles contain the enzymes for the citric acid cycle, electron transport chain, and oxidative phosphorylation, facilitating ATP production.
5. Endoplasmic Reticulum (ER): The rough ER (studded with ribosomes) is involved in protein synthesis and folding, while the smooth ER is essential for lipid synthesis and detoxification processes.
6. Golgi Apparatus: Functions in the modification, sorting, and packaging of proteins and lipids for secretion or delivery to other organelles.
7. Lysosomes: Contain hydrolytic enzymes that break down macromolecules, old organelles, and foreign substances, maintaining cellular homeostasis.

Energy Rich Compounds:

Energy-rich compounds are molecules that store chemical energy in their bonds, which can be released to drive endergonic biological processes. The most significant of these is Adenosine Triphosphate (ATP).

ATP acts as the universal energy currency of the cell. Its high-energy nature is due to the presence of phosphoanhydride bonds; the hydrolysis of the terminal phosphate group releases approximately 30.5 kJ/mol of energy under standard conditions. Other important energy-rich compounds include:

• Phosphoenolpyruvate (PEP): Contains a high-energy phosphate bond and serves as a major phosphate donor in glycolysis.
• 1,3-Bisphosphoglycerate: An intermediate in glycolysis with a high group-transfer potential.
• Creatine Phosphate: Functions as a rapid energy reserve in muscle and brain tissues to regenerate ATP.
• Thioesters (e.g., Acetyl-CoA): These compounds contain a high-energy sulfur bond, which is crucial for the transfer of acyl groups in metabolic pathways like the citric acid cycle.