JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Pharmacy III CELL AND MOLECULAR BIOLOGY Previous Question Paper (March-2021 - R17)

The cell membrane, or plasma membrane, acts as a selective barrier that maintains the integrity and internal environment of the cell. Its primary functions include:

• Selective Permeability: It regulates the transport of ions, nutrients, and waste products into and out of the cell through passive diffusion, facilitated diffusion, and active transport.
• Structural Support and Protection: It provides mechanical support and defines the boundary of the cell, separating the cytoplasm from the external environment.
• Cell Signaling: Membrane proteins act as receptors that bind to specific signaling molecules (ligands) such as hormones or neurotransmitters, initiating intracellular responses.
• Cell Recognition and Adhesion: Glycoproteins and glycolipids on the surface serve as markers for cell-to-cell recognition and facilitate adhesion to neighboring cells or the extracellular matrix.
• Enzymatic Activity: Certain membrane proteins function as enzymes that catalyze metabolic reactions occurring at the cell surface.

The fundamental difference between prokaryotic and eukaryotic cells lies in their structural complexity and the presence of membrane-bound organelles.

Prokaryotes, such as bacteria, are generally unicellular, lack internal compartmentalization, and possess a simple genome. In contrast, eukaryotes, including plants, animals, and fungi, feature complex internal structures, membrane-bound organelles like the nucleus and mitochondria, and a more sophisticated mechanism for gene expression and regulation.