BIOL 1111 Chapter 23: Chapter 23
Document Summary
Viruses cannot reproduce their own and lack a metabolic system to provide energy for their life cycles. Structure of a virus is reduced to the minimum necessary to transmit its genome from one host to another. It is one or more nucleic acids surrounded by a protein coat or capsid. Some capsids may be enclosed within a membrane/envelope derived from their host cells membrane. All viruses have genes that encode at least their coat proteins, as well as proteins involved in regulation of transcription. Genomes of enveloped viruses also include genes required for the making of envelope proteins. Most viruses are either helical or polyhedral: helical viruses. Proteins form in rodlike spiral around genome. Protein spikes proved host cell recognition extending from the corners. Both can be enveloped in a membrane derived from the host cell. Viruses are classi ed into orders, families, genera and species: virus size, structure, genome structure and replication.