Correct option is D
Explanation-
Option D - Cholesterol is abundant in mammalian plasma membranes. It helps in maintaining membrane fluidity, stabilizing membrane structure. It is absent in most prokaryotes (bacteria do not synthesize cholesterol). It is absent or minimal in plant cells – instead, plant cells use phytosterols (like stigmasterol) for similar functions.
Incorrect options-
Option A - Phosphoglycerides
It represent a major class of phospholipids (e.g., phosphatidylcholine, phosphatidylethanolamine). It is found in all biological membranes – including prokaryotes, plants, and animals. Although they are abundant, they are not exclusive to mammalian membranes.
The question asks for something abundant in mammalian cells but absent in most prokaryotes and plants – which doesn’t apply to phosphoglycerides.
Option B - Ergosterol
Sterol found in fungal cell membranes, playing a role similar to cholesterol in animals. It is not found in mammalian membranes at all. It is present in fungi, not in prokaryotes or plants either.
Option C - Choline
Choline is a nutrient or precursor involved in synthesis of phosphatidylcholine. It exists as a small molecule, not a membrane component on its own. Choline itself is not a structural component of membranes. It’s used in biosynthesis of some membrane phospholipids, but not abundantly embedded in membranes like cholesterol is.
Also not absent from prokaryotes or plants, as choline derivatives may exist in various organisms.
So, the correct answer is option D- Cholestrol.
