Viruses Higher Human Biology Lesson Aims • To describe the structure of a virus • To examine the process of viral replication Different types of viruses • Influenza virus • AIDS virus Different Shaped Viruses Size • Smaller than bacteria • 20-300 nanometres (nm) Structure of a Virus • A virus contains nucleic acid (DNA or RNA) • Surrounded by a protective coat (capsid) Entering the Host Cell • Different viruses employ different methods of entering the host cell • Process depends on antigenic sites on the virus binding with certain complementary molecules in the membrane or the specific host cell • Following binding the nucleic acid is introduced into the host cell Binding With the Host Cell Assembly of New Viruses • Once in the host cell the virus assumes control of the cell’s biochemical machinery • Host cell supplies energy (ATP), nucleotides, amino acids • Host then makes many identical copies of viral nucleic acid and protein coats . Viruses Higher Human Biology Lesson Aims • To describe the structure of a virus • To examine the process of viral replication Different types of viruses • Influenza. Different types of viruses • Influenza virus • AIDS virus Different Shaped Viruses Size • Smaller than bacteria • 20-300 nanometres (nm) Structure