Presentation on theme: "1. Review What do viruses depend on for their reproduction 2. Review Describe each of the two paths viruses may follow once they have entered a cell 3."— Presentation transcript:
1. Review What do viruses depend on for their reproduction 2. Review Describe each of the two paths viruses may follow once they have entered a cell 3. Compare and Contrast Compare the structure of a virus to the structure of both a prokaryotic cell and a eukaryotic cell. Use a graphic organizer of your choice to organize the information
Viruses Nonliving particle made of proteins, nucleic acids, and sometimes lipids Can reproduce only by infecting living cells Wide variety of size and structure Very small Need electron microscope to see.
Capsid Protein coat surrounding a virus Proteins on their surface membrane that trick receptor cells on host cell into accepting its genetic material Contain a few to a few hundred genes.
Most viruses infect only a very specific kind of cell Bacteriophages Viruses that infect bacteria Plant viruses infect plant cells Most animal viruses infect only certain related species of animals.
Lytic Infections Virus enters a bacterial cell Makes copies of itself Causes the cell to burst, or lyse Bacteriophage T4.
Copy inserts itself into the DNA of the host cell.
HIV is similar to a lysogenic infection Viral DNA may remain inactive for many cell cycles before making new virus particles and damaging the cells of the host’s immune system.
Viruses must infect living cells in order to grow and reproduce, taking advantage of the nutrients and cellular machinery of their hosts After infecting living cells, viruses can reproduce, regulate gene expression, and even evolve.