Q. The biological membranes are composed of:

Correct Answer: a) Lipids and proteins in varying combinations which are specific to each species, cell type and organelle

Explanation:
– Biological membranes follow the fluid mosaic model: a phospholipid bilayer with embedded and peripheral proteins.
– Carbohydrates are also present, attached to lipids and proteins (glycolipids and glycoproteins), but the core components are lipids and proteins.
– The lipid-to-protein ratio varies by species, cell type, and organelle (e.g., myelin is lipid-rich, while the inner mitochondrial membrane is protein-rich).
– Therefore, options “lipids only” or “proteins only” are incorrect.