Final answer:
Viruses contain nucleic acids (either RNA or DNA), a protective protein coat called a capsid, and sometimes an outer lipid envelope with glycoproteins for attaching to host cells. They carry enzymes such as reverse transcriptase for replication.
Step-by-step explanation:
Viruses contain various components that are crucial for their ability to infect host cells and reproduce. One of the essential elements of viruses is their nucleic acids, which can be either DNA or RNA but never both. These nucleic acids contain the genetic information necessary for the virus to replicate. Surrounding the nucleic acid is a protein coat called a capsid, composed of subunits known as capsomeres. Some viruses also have a lipid envelope derived from the host cell's membrane, studded with viral proteins, including glycoproteins that help viruses attach to and enter host cells. While viruses use the host cell's replication machinery to reproduce, they often carry specific viral enzymes, like reverse transcriptase in retroviruses, to aid in the replication process.