How do viruses differ from bacteria in terms of structure?

Viruses are fundamentally different from bacteria in terms of their structure, primarily because they consist of genetic material, either DNA or RNA, enclosed in a protein coat called a capsid. This unique organization is essential to their function as viruses cannot replicate by themselves. Instead, they must infect a host cell and hijack the host's cellular machinery to reproduce. This contrasts with bacteria, which are unicellular organisms with a complex structure that includes a cell wall, membrane, cytoplasm, and ribosomes, allowing them to carry out metabolic functions independently.

The presence of just a protein coat encasing genetic material highlights the simplicity of viral structure compared to the more complex cellular architecture of bacteria. This is why the description of viruses having their genetic material encapsulated within a protein coat is the defining characteristic that distinguishes them from bacteria.