dna dsdna is most viruses acid can dna nucleic acid can nucleic rna can dna rna can dsdna partial can complete dsdna can complete partial can dsdna ssdna can dna ssdna can dna dsdna attach cell function host proteins surface capsid form helical rod-shaped is less rna stable acid all central core have nucleic covering envelope have some acid capsid consists nucleic acid consists nucleic nucleocapsid capsid consists nucleocapsid capsid form hexons icosahedral triangular capsid form icosahedral pentons round form hexons pentons round triangular capsomers form protomers all capsid covering have are capsomers polypeptides that can negative polarity ssrna can polarity positive ssrna ambisense can ssrna can negative polarity positive ambisense can negative polarity ambisense can polarity positive bilayer made phospholipid proteins lipids made proteins bilayer lipids made phospholipid central consist core viruses central consist core covering consist covering viruses can capsomers rod-shaped acid digestion nucleic protect capsomers function protect cell function host penetrate protect attach cell function host protect capsomers cell function host penetrate attach capsomers cell function host attach cell function host penetrate acellular all are ultramicroscopic all are intracellular obligate parasites ultramicroscopic all are ultramicroscopic viruses acellular all are intracellular obligate parasites acellular all are viruses all are intracellular obligate parasites viruses all capsid have helical negative polarity is most rna ssrna viruses central core have proteins some function matrix proteins stabilize virus can rna ssrna can dsrna ssrna can dsrna rna can capsomers hexons triangular can hexons pentons round triangular can capsomers pentons round can matrix proteins can proteins surface can matrix proteins surface capsid function genome is protect capsid capsomers made during function na proteins replication stabilize aid during enzymatic function functions na other replication stabilize actual during function na perform replication stabilize aid enzymatic function functions other proteins actual function perform proteins replication actual aid enzymatic function functions other perform replication 3' 5' as cell is mrna polarity positive same which bilayer envelope made phospholipid as known peplomers proteins surface as known peplomers spikes as known proteins spikes surface