How are viroids different from viruses?

Viroids are smaller than viruses and consist solely of a short, single-stranded, low molecular weight RNA molecule. Unlike viruses, viroids lack a protein coat (capsid) and do not contain any protein components. They infect plants and cause diseases such as potato spindle tuber disease without requiring a protein coat for their activity. In contrast, viruses are nucleoproteins with a protein coat called capsid that protects their genetic material, which can be either RNA or DNA, and they are obligate parasites that infect various hosts, including animals and plants.