Non-Living Infectious Agents Viruses
What are they? How do they work? Where do they come from? And What good are they? Non-viral Infectious Agents
Viroids- The smallest known particle that can replicate. Single Strand of RNA Disrupt plant cell metabolism Can destroy entire crops Prions Abnormal forms of proteins that clumptogether inside cells. Clumping eventually kills the cell Example Mad Cow Disease Overview of Viruses Nonliving Composed of Nucleic acid and protein
Cause many diseases Virology Study of Viruses Comparison of Viruses and Cells below Char. Of Life Virus Cell Growth No Yes Homeostasis Metabolism Mutation Nucleic acid DNA or RNA DNA Reproduction Only within host cell Independently by cell division Structure Nucleic acid core, protein covering, some have envelope Cytoplasm, cell membrane, etc.. Characteristics of Viruses
2 essential features 1. Nucleic Acid May be DNA or RNA Helical, closed loop, or long strand 2. Protein Coat called CAPSID Some have ENVELOPE Ex.Influenza, chickenpox, herpes simplex, HIV VIRAL SHAPE Icosahedron 20 triangular faces Ex.) herpes, chickenpox, polio Helix Coiled spring EX.) Rabies, measles, tobacco mosaic Bacteriophages: like tiny little syringes that injectDNA from the virus into the cell Lytic Cycle 1. Attachment- Virus finds host cell Host cell DNA
Bacteriophage Host cell DNA 1. Attachment- Virus findshost cell 2. Entry- Viral DNAinjected into host 3. Replication- Host makesviral DNA & parts 4. Assembly- New viruses made 5. Lysis & Release-viruses burst out of host(dies); Find new host Here is a non-enveloped bacteria virusinserting its DNA into a bacterial cell. Some virus are pushed out by the cell,taking some of the cell membrane with them. Lysogenic Cycle After Step #2 of the Lytic Cycle, the Virusmay become Dormant and enter into theLysogenic cycle Dormant- non-active time of virus Host is infected, but doesnt know it Ex: Herpes (cold sores) Person doesnt havethem all the time, but has outbreaksthroughout year Ex: HIV Mono Lysogenic Cycle From Step #2 Lytic cycle, enters Lysogenic cycle here
2. Entry- Viral DNAinjected into host 3. Integration - Viral DNAbecomes part of host DNA 4. Cell Multiplication Hostreplicates with viral DNA Many celldivisions 5. Cell enters back into Lytic Cycle-Assemble, Lysis & Release Provirus Classification of Viruses
1. By Shape Host type function Retroviruses attacka certain way. DNA viruses attackanother way. Animal viruses Plant viruses Bacteria viruses Viruses and Human Disease
Control and Prevention of spread. Vaccination & Antiviral drugs Ex.) chickenpox vaccine, AZT, Acyclovir, proteaseinhibitors. Emerging Viruses exist in isolated habitats Do not usually infect humans unlessenvironmental conditions favor contact. Several viruses are now linked to cancerssuch as leukemia, liver cancer, Burkittslymphoma, cervical cancer. English physician and scientist from Berkeley, Gloucestershire, who was the pioneer of smallpox vaccine Cowpox and smallpox are closely related, but cowpox is a much less serious disease than smallpox.
Jenner noticed milkmaids were immune to smallpox. He used puss from a cowpox blister to inocculate an 8 year old boy He called his method vaccination, from the Latin word vacca, or cow, and today we use vaccination to refer to immunization against any disease. A vaccine contains a killed/weakened part of a germ.
When a person receives a vaccine, the body reacts by making protective antibodies. Wendell M. Stanley Wendell M. Stanley crystallized and described the molecular structure of the tobacco mosaic virus. PAPOVAVIRUSES:Tumor causing viruses Most common:Human papillomavirus (HPV) (warts) ADENOVIRUSES: causes respiratory issues and pink eye HERPESVIRUSES: easily transmitted by direct contact with a lesion or the body fluid of an infected individual POXVIRUSES PICORNAVIRUSES The name is derived from pico, meaning small, and RNA, referring to the ribonucleic acid genome, so "pico-rna-virus" literally means small RNA virus. Ranges from the common cold to polio! MYXOVIRUSES RHABDOVIRUSES RETROVIRUSES: genes are encoded in RNA instead of DNA Here is a classic picture of HIV viralprogeny being released from thesurface of a T- cell.Notice themembrane coating they receive. Ebola Virus Some therapies that have worked havebeen when patients receive blood fromconvalescent patients 26