Computer graphics representation of the external structure of a virus causing AIDS (Acquired Immune Deficiency Syndrome). The AIDS virion (virus particle), designated Human Immunodeficiency Virus diameter. The particle is covered by a membrane (yellow), made up of two layers of lipid (fatty material) derived from the outer membrane of the host cell. Studding the membrane are glycoproteins, each divided into 2 components: gp41 (red) spans the membrane and gp120 (blue) extends beyond it. The membrane/protein envelope covers a core containing the viral RNA.