Explanation

Ribosomes are very small organelles having a diameter of 150 Å – 250 Å. Each ribosome is made up of two subunits, a smaller subunit and another larger subunit. These two subunits are associated with the help of Mg²⁺ ions (at 0.001 M concentration). If the Mg²⁺ ions concentration is less in cytoplasm, the two units of ribosome separate but when the Mg²⁺ ions concentration is increased ten times, the two unites and form a dimer.