Obligate parasite - cannot grow independently of host or cell, no metabolism except following infection of cell. Incapable of multiplying independently (do(cid:374)"t t(cid:455)pi(cid:272)all(cid:455) sa(cid:455) (cid:448)i(cid:396)uses (cid:396)ep(cid:396)odu(cid:272)e (cid:271)(cid:272) (cid:373)ost ppl do(cid:374)"t consider them living, but can increase in # Dna or rna genome - most cellular living things have both. Absence of dna and rna together in the same virion. Envelope is not coded by the virus. Protects the genome from physical, chemical and enzymatic conditions. In naked viruses, need to get into cell - viruses have spikes (proteins) found on nucleocapsid representing viral key or viroreceptor that recognizes and binds to cellular receptor lock so virus can enter that cell. Enveloped - not found on nucleocapsid but on envelope: lipid bilayer removal lose key and therefore cannot bind. Has receptor proteins (spikes) that enable the recognition and attachment to the host cell. For some viruses, the capsid is surrounded by a lipid bilayer.