Question

Why are viruses described as acellular?

Answer 1

A virus is a small infectious agent that replicates only within an organism's live cells. Viruses infect all living things, including bacteria and archaea, from mammals and plants to microbes. Since Dmitri Ivanovsky's 1892 publication identifying a non-bacterial disease infecting tobacco plants and Martinus Beijerinck's 1898 discovery of the tobacco mosaic virus.

Complete answer:
Viruses are acellular, which means they don't have a cellular structure. As a result, they lack the majority of cell components such as organelles, ribosomes, and the plasma membrane. Viruses are frequently referred to as virions: a virion is a virus that is ‘completely' free of infection in the environment (not in a host). A virion has a nucleic acid core and an outer protein coating or capsid;
Some viruses also have an outer envelope consisting of protein and phospholipid membranes from the host cell. Additional proteins, such as enzymes, may be found in viruses. The most noticeable distinction between members of viral families is their morphology, which varies greatly.
The host's complexity does not correspond with the virion's complexity, which is an intriguing characteristic of viral complexity. Bacteriophages, viruses that infect the simplest living species, bacteria, have some of the most complicated virion architectures.
Nucleic Acid Types-
Viruses, unlike nearly all other living things, can employ either DNA or RNA as their genetic material. The virus's genome, or whole genetic content, is contained in the virus core. Viral genomes are typically short, with just those genes encoding proteins that the virus cannot obtain from the host cell. It's possible that this genetic material is single-stranded or double-stranded.It may also be linear or circular.
Human diseases like chickenpox, hepatitis B, and various venereal diseases like herpes and genital warts are caused by DNA viruses. Hepatitis C, measles, and rabies are all diseases caused by RNA viruses.
Morphology-
Viruses occur in a variety of shapes and sizes, but each viral family has its own set of characteristics. A protective coating of proteins called a capsid surrounds the nucleic acid genome of all virions. Capsomeres are protein subunits that make up the capsid. Some viral capsids have basic polyhedral "spheres" in their structure, whereas others have more complicated structures.
Many viruses employ glycoproteins to adhere to their host cells via viral receptors, which are molecules on the cell surface.

Note:-
The T4 bacteriophage, which infects the Escherichia coli bacteria, features a tail structure that the virus uses to connect to host cells and a head shape that holds its DNA, making it one of the most complicated virions known. Overall, the virion's form and the existence or lack of an envelope reveal little about the disease the virus may cause or the species it may infect, but they are nevertheless important tools for identifying viruses.