The document discusses key characteristics and properties of viruses. It notes that viruses are microscopic particles that infect cells and often destroy them. Viruses are smaller than bacteria, change rapidly, and there are many unknown types. Their small size and rapid mutation make viruses difficult to treat. The document then describes viruses as obligate intracellular parasites that are non-cellular, replicate by taking over host cell machinery, and lack their own metabolism or protein synthesis abilities. Finally, it briefly discusses virus shapes, taxonomy, and references used.

1. VIRUSES
Presented
By
Kanchan Sinha
ShriShankaracharyaMahavidyalaya,Junwani,Bhilai

2. INTRODUCTION
• Virus: a microscopic particle that gets inside a
cell and often destroys the cell
• Viruses are tiny
• Smaller than the smallest bacteria
• Change rapidly
• So small and change so often that scientists
don’t know exactly how many types exist
• These properties make viruses difficult to fight

3. Definition

4. HISTORY

7. CHARACTERISTICS OF VIRUS
• Viruses are obligate intracellular parasites of bacteria,
protozoa, fungi, algae, plants, and animals.
• Ultramicroscopic size, ranging from 20 nm up to 450 nm
(diameter). Viruses are smaller than bacteria.
• Not cellular in nature; structure is very compact and
economical.
• Do not independently fulfill the characteristics of life.
• Inactive macromolecules outside the host cell and active
only inside host cells.
• Basic structure consists of protein shell (capsid)
surrounding nucleic acid core.
• Nucleic acid can be either DNA or RNA but not both.

8. CHARACTERISTICS OF VIRUS
• Nucleic acid can be double-stranded DNA, single- stranded DNA single-
stranded RNA, or double-stranded RNA.
• Molecules on virus surface impart high specificity for attachment to host
cell.
• Multiply by taking control of host cell’s genetic material and regulating
the synthesis and assembly of new viruses.
• Viruses lack cellular organelles, such as mitochondria and ribosomes.
• Lack ribosome and enzymes needed for metabolism .
• Use the raw materials and enzymes of the host cell to be able to
reproduce .
• Lack machinery for synthesizing proteins.
• Most RNA viruses multiply in & are released from the cytoplasm.
• Viral infections range from very mild to life threatening.
• Viruses are parasites-A parasite is an organism that depends upon another
living organism for its existence in such a way that it harms that organism

10. SHAPES OF VIRUS
• There are four main shape of virus -

12. TAXONOMY OF VIRUSES
• Family names end in -viridae
• Genus names end in -virus
• Viral species: A group of viruses sharing the same genetic information and
ecological niche (host).
• Common names are used for species.
• Subspecies are designated by a number.

17. REFERENCES
• https://www.slideshare.net/RIZWANABBAS3/viru
ses-structure-classification-and-characteristics
• https://www.slideshare.net/vidhyakalaivani29/vir
usessizeshape-types
• https://www.slideshare.net/kmtschida/virus-
powerpoint
• https://www.slideshare.net/jdrinks/viruses-ppt-
15932866
• https://www.slideshare.net/rajendra930136/viru
s-23717258?next_slideshow=1