INTRODUCTION
• Study of viruses are called virology.
• Viruses are small cellular agents.
• Outside host cells, they have non living
• characteristics.
• They cannot grow and multiply.
• They may consist of only one type of nucleic acid(either RNA or DNA
• These nucleic acids has protein coat.
• Protein coat protects nucleic acids from external environment.
• It also helps virion to attach to the host cell membrane.
• Virion penetrates into host cells and starts replication.
,• Viruses are dependent upon host cells for synthetic protein and energy
requirements.
• Their multiplication cause damage to host cells.
• Generally they do not cause death of host except HIV, ebola virus, rabies
virus and hantavirus.
,STRUCTURE OF A VIRUS
, GENERAL CHARACTERISTICS
• Viruses are particles and consist of either DNA or RNA.
• Nucleic acid( DNA or RNA) is covered with protective protein
coat.
• Some viruses have outer lipoprotein membrane . This outer
lipoprotein membrane is called envelope.
• They do not have nucleus, cytoplasm, mitochondria, ribosome
or any other cellular organelles.
• They behave as non living outside host cells because they
cannot generate energy or synthesize proteins.
• They do not have any metabolic enzymes.
• Study of viruses are called virology.
• Viruses are small cellular agents.
• Outside host cells, they have non living
• characteristics.
• They cannot grow and multiply.
• They may consist of only one type of nucleic acid(either RNA or DNA
• These nucleic acids has protein coat.
• Protein coat protects nucleic acids from external environment.
• It also helps virion to attach to the host cell membrane.
• Virion penetrates into host cells and starts replication.
,• Viruses are dependent upon host cells for synthetic protein and energy
requirements.
• Their multiplication cause damage to host cells.
• Generally they do not cause death of host except HIV, ebola virus, rabies
virus and hantavirus.
,STRUCTURE OF A VIRUS
, GENERAL CHARACTERISTICS
• Viruses are particles and consist of either DNA or RNA.
• Nucleic acid( DNA or RNA) is covered with protective protein
coat.
• Some viruses have outer lipoprotein membrane . This outer
lipoprotein membrane is called envelope.
• They do not have nucleus, cytoplasm, mitochondria, ribosome
or any other cellular organelles.
• They behave as non living outside host cells because they
cannot generate energy or synthesize proteins.
• They do not have any metabolic enzymes.
