Diagram showing typical examples of a virus particle (above) and a bacterium (below). Virus particles, or virions, generally consist of two or three parts: the genetic material made from either DNA or RNA; a protein coat that protects these genes; and in some cases, a lipid envelope that surrounds the protein coat. Also shown are glycoprotein spikes, which function to attach the virus to receptors on succeptible host cells. Bacterial cells, while similar in structure to virions, are generally much larger, with a more complex structure.