Given below are four pairs of cellular structures and their descriptions: (I) Cristae : Infoldings of the inner mitochondrial membrane (II) Cisternae : Flattened membranous sacs in the stroma of chloroplast (III) Thylakoids : Disc-shaped sacs in the Golgi apparatus (IV) Mesosome : Membranous extension into the cytoplasm of prokaryotes How many of the above pairs are correctly matched?

Step-by-step solution

(I) Cristae are the infoldings of the inner mitochondrial membrane. (Correct) (II) Cisternae are the flat, disc-shaped sacs present in the Golgi apparatus, not the chloroplast. (Incorrect) (III) Thylakoids are the flattened membranous sacs present in the stroma of the chloroplast, not the Golgi apparatus. (Incorrect) (IV) Mesosomes are formed by the extensions of the plasma membrane into the cell in prokaryotes. (Correct) Therefore, exactly two pairs (I and IV) are correctly matched. Answer: Only two