Which one of the cell organelles is not enclosed by any membrane?

Options

(a) lysosome
(b) ribosome
(c) mitochondria
(d) plastid

Correct Answer:

ribosome

Explanation:

Ribosomes are naked ribonucleoprotein protoplasmic particles which function as the site for protein synthesis. Therefore they are popularly known as protein factories. Ribosomes are produced in nucleolus and occur on nuclear membrane & RER. It is also present in cytoplasm in prokaryotes and eukaryotes. Chemically ribosome is made up of rRNA (60%) protein (40%). As ribosomes, nucleolus and centrioles are also membrane less cell organelles.