Final answer:
All viruses have a nucleic acid genome and a protein capsid, but not all have an envelope. The protein capsid is made of capsomeres and envelopes, when present, are derived from host cell membranes.
Step-by-step explanation:
All viruses possess a nucleic acid genome (either DNA or RNA but never both) and a protein capsid. The protein capsid is composed of smaller protein subunits known as capsomeres. It's also important to note that not all viruses have an envelope; this feature varies among different viral families. Those viruses with an envelope derive it from the host cell's membrane structures, which can be studded with viral proteins such as glycoproteins that facilitate attachment to host cells.