NEET BIOLOGY

Detailed explanation-1: -Viruses are ultramicroscopic because they range in size from 2 mm to 450 mm. A specific animal virus has the ability to attach to and enter almost any animal host cell. Viruses are the most common cause of acute infections that do not result in hospitalization. Viruses are simple, noncellular, and lack mRNA.

Detailed explanation-2: -Viruses are ultramicroscopic (<0.2µm) in size which necessitates that an electron microscope be used to see them. The virus consists of a viral capsid (a protective outer protein shell), that encases a nucleic acid (DNA or RNA, but not both), and possibly an envelope.

Detailed explanation-3: -Viruses are ultramicroscopic (typically 20–300 nm in diameter) infectious agents that only replicate within the cells of living hosts. They are composed of an RNA or DNA core, a protein coat, and, in more complex types, a surrounding lipid envelope derived from the plasma membrane of the host cell.

Detailed explanation-4: -Virus and cell size comparison. Human viruses can vary in size but are generally in the range of 20–200 nm in diameter. In comparison, bacteria are generally 2–3 M in length, and an average human cell is 10–30 M.

Detailed explanation-5: -Size of virus particles commonly is determined three ways: (1) Electronmicroscopy (2) Ultrafiltration and (3) Ultracentrifugation. and density gradient ultracentrifugation to determine size of a virus believed to be one cause of Infectious Bovine Keratitis (IBK). cells.