Name and briefly describe the three major classes of eukaryotic biological membranes.

Answer: The three major classes of eukaryotic biological membranes are the plasma membrane, mitochondrial membranes, and the endomembrane system. The plasma membrane surrounds the cell, protects it, and controls the passage of substances in and out of the cell. Mitochondrial membranes are involved in energy production, with the outer membrane allowing the passage of small molecules and ions, and the inner membrane hosting the electron transport chain and ATP synthase. The endomembrane system consists of a network of interconnected membranes such as the nuclear envelope, endoplasmic reticulum, Golgi apparatus, and vesicles, which perform various functions including enclosing genetic material, protein synthesis and modification, lipid synthesis, and molecular transport.