How does the structure of a virus differ from a cell?

A virus is much smaller than a cell and lacks cellular structures like a nucleus, mitochondria, or cytoplasm.

Viruses and cells are both fundamental units of life, but they differ significantly in their structure and complexity. A virus is an infectious agent that is much smaller than a cell and lacks the cellular structures that are characteristic of a cell. Unlike cells, viruses do not have a nucleus, mitochondria, or cytoplasm. They also do not have the machinery to carry out metabolic processes, which is why they are often referred to as 'acellular' or 'non-living' entities.

The structure of a virus is relatively simple. It consists of a protein coat, known as a capsid, which encloses its genetic material. This genetic material can be either DNA or RNA, but not both. Some viruses also have an outer envelope made of lipids. The capsid and the envelope (if present) protect the genetic material and help the virus to attach to and enter host cells.

On the other hand, a cell is a complex structure that contains a variety of organelles, each with a specific function. These include the nucleus, which houses the cell's DNA, the mitochondria, which produce energy, and the cytoplasm, a jelly-like substance that fills the cell and houses the organelles. Cells also have a plasma membrane that controls the movement of substances in and out of the cell.

In terms of reproduction, viruses and cells also differ. Viruses cannot reproduce on their own; they need to infect a host cell and use its machinery to replicate. This is in contrast to cells, which can reproduce independently through a process called cell division.

In summary, while viruses and cells are both crucial to the study of biology, they are structurally very different. A virus is a simple structure that lacks the organelles found in cells and relies on host cells to reproduce. A cell, meanwhile, is a complex structure capable of carrying out a wide range of functions and reproducing independently.