Fig. (2) A host cell bearing receptors of SARS-Cov-2; ACE-2. Cell infection by the virus involves priming of the S spike glycoprotein of the virus by cellular serine proteases and possibly by other extracellular serine proteases. Priming of the S spike protein allows the virus to pursue its entry into the host cell, and proceed to the rest of the biochemical steps for its RNA and protein synthesis, followed by virion assembly.