Acellular may be defined as a set of organisms that do not have a cellular structure. Protein compounds with a certain configuration, capable of transforming into pathogens and causing neurodegenerative processes in the body, were called prions. Prions constitute a separate class of infectious agents; they have a protein base and do not contain a genome consisting of nucleic acids.
The prion molecule, in its “normal” form, is found on the surface of nerve cells in every person. Ordinary protein molecules, coming into contact with pathological ones, themselves turn into them while changing their own spatial structure. What the trigger for such a transformation is not fully known. It follows from this that the prion, acting as an infectious agent, infects normal molecules, causing a “molecular epidemic.”
Simply organized viruses are nucleoproteins or nucleocapsids. They consist of nucleic acid (RNA or DNA) and several encoded proteins that form the viral envelope – the capsid. Complexly organized viruses contain additional outer shells and have a more complex composition – proteins, lipids, and glycoproteins.