Final answer:
The structure of a virus is different from a prokaryotic cell mainly because viruses lack a cell membrane and the cellular components required for independent life processes, relying on a host cell for replication.
Step-by-step explanation:
The structure of a virus is different from that of a prokaryotic cell because viruses are not bound by a cell membrane (option A). Unlike prokaryotic cells, which have a cell membrane, cytoplasm, and other structures, a virus typically consists of a nucleic acid core, a protein coat called a capsid, and in some cases, an outer envelope derived from the host cell.
Prokaryotic cells, on the other hand, are made of cells with a plasma membrane and lack a membrane-bound nucleus, but they do possess genetic material in the form of DNA or RNA in a region called the nucleoid, and they have ribosomes for protein synthesis. Viruses, while they do contain genetic material (either DNA or RNA), cannot replicate or carry out metabolic processes on their own and must infect host cells to do so. This lack of independent reproductive and metabolic capabilities is part of why viruses are not considered living. They are acellular, meaning they lack cell structures like ribosomes and are unable to perform life-sustaining functions without a host.