Answer
Ribosome, the primary structure studied by Venki Ramakrishnan, is a complex molecular machine responsible for protein synthesis in cells. It is composed of two subunits, a large and a small subunit, each containing ribosomal RNA (rRNA) and proteins. Ramakrishnan's research focused on the structure and function of the ribosome, particularly the large subunit, and his work has provided insights into the intricate mechanisms of protein synthesis.