A cell biologist isolates ribosomes from two different fractions of a plant mesophyll cell: the general cytoplasm and the stroma of the chloroplast. Which of the following correctly identifies the type and subunit composition of the ribosomes found in these two locations respectively?

Step-by-step solution

In a eukaryotic plant cell, the ribosomes present in the general cytoplasm are of the 80S type. The two subunits of an 80S ribosome are 60S and 40S. However, semi-autonomous organelles like chloroplasts and mitochondria contain their own ribosomes, which are smaller and prokaryotic-like, i.e., 70S. The two subunits of a 70S ribosome are 50S and 30S. Therefore, the cytoplasm contains 80S (60S and 40S) ribosomes, while the chloroplast stroma contains 70S (50S and 30S) ribosomes. Answer: Cytoplasm: 80S (60S and 40S) ;