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 life, acting as a highly organized biochemical system. Its organization is defined by compartmentalization, which allows for the simultaneous occurrence of diverse metabolic processes.

Biochemical Organization of the Cell:

• Plasma Membrane: A selectively permeable lipid bilayer containing integral and peripheral proteins. It regulates the transport of ions, nutrients, and waste, and facilitates cell signaling.
• Cytoplasm and Cytosol: The aqueous environment containing dissolved enzymes, metabolites, and electrolytes. It is the site of glycolysis, fatty acid synthesis, and protein synthesis via ribosomes.
• Nucleus: The repository of genetic material (DNA). It controls cellular activities through gene expression, transcription, and replication.
• Mitochondria: The powerhouses of the cell, containing the machinery for the citric acid cycle, oxidative phosphorylation, and the electron transport chain, which generate ATP.
• Endoplasmic Reticulum (ER): The rough ER (studded with ribosomes) is responsible for protein synthesis and folding, while the smooth ER is involved in lipid biosynthesis and detoxification.
• Golgi Apparatus: Functions in the modification, sorting, and packaging of proteins and lipids for secretion or delivery to other organelles.
• Lysosomes: Membrane-bound vesicles containing hydrolytic enzymes that degrade macromolecules, cellular debris, and foreign pathogens.

Energy-Rich Compounds:

Energy-rich compounds are molecules that store chemical energy in their bonds, which can be released to drive endergonic biological reactions. The most significant is Adenosine Triphosphate (ATP), often called the universal energy currency.

ATP contains two high-energy phosphoanhydride bonds. When these bonds are hydrolyzed to form ADP and inorganic phosphate (Pi), a large amount of free energy is released (ΔG'° ≈ -30.5 kJ/mol). Other important energy-rich compounds include:

• Phosphoenolpyruvate (PEP): Contains the highest phosphate group transfer potential in glycolysis.
• 1,3-Bisphosphoglycerate: An intermediate in glycolysis that provides energy for ATP synthesis.
• Creatine Phosphate: Acts as a rapidly mobilizable reserve of high-energy phosphates in skeletal muscle.
• Acetyl-CoA: A thioester compound that serves as a central intermediate in the metabolism of carbohydrates, fats, and proteins, carrying acetyl groups for the citric acid cycle.