Characteristics of viruses:

• They are enclosed in a protective envelope.
• They have spikes, which helps them to attach to the host cell.
• They are non cellular.
• They do not respire, do not metabolize and do not grow but they do reproduce.
• They contain a protein coat called the capsid.
• They have a nucleic acid core containing DNA or RNA.
• Ribosomes and enzymes are absent, which are needed for metabolism.
• They are considered both as living and non living things, as viruses are inactive when they are present outside of host cells and are active in side of host cells. As they make use of raw materials and enzymes of the host cell to reproduce and causes several infections.