Question

What is s in $70$s?

Answer 1

Ribosomes are the sites for protein synthesis. Several ribosomes may attach to a single mRNA and form a chain called polyribosomes or polysomes. The ribosomes of a polysome translate the mRNA into proteins. The "S" stands for svedbergs, a unit used to measure how fast molecules move in a centrifuge. Bacteria and archaebacteria have smaller ribosomes, have 70S ribosomes, which are composed of a small 30S subunit and large 50S subunit.