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Download Viruses, bacteria, viroids, and prions can all cause infection.
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Viruses, bacteria, viroids, and prions can all cause infection. • Any disease-causing agent is called a pathogen. 1 nanometer (nm) = one billionth of a meter 100 nm eukaryotics cells 10,000-100,000 nm viruses 50-200 nm prokaryotics cells 200-10,000 nm viroids 5-150 nm prion 2-10 nm Viruses differ in shape, genetic material, and in ways of entering host cells. – non-living pathogen – can infect many organisms • Viruses have a simple structure. – genetic material (either DNA or RNA) – capsid, a protein shell – maybe a lipid envelope, a protective outer coat Viral Shapes: depends on proteins of capsid enveloped (influenza) capsid nucleic acid lipid envelope helical (rabies) Surface proteins capsid nucleic acid surface proteins lipid envelope polyhedral (foot-and-mouth disease) surface proteins capsid nucleic acid • A bacteriophage is a virus that infects a bacterium. capsid HEAD DNA collar tail sheath TAIL Base plate tail fiber • Viruses enter cells in various ways. – bacteriophages pierce host cells – viruses of eukaryotes enter by endocytosis or fuse with the membrane LYTIC CYCLE New vocab words from the cut-out activity: • Host- the cell the virus is infecting • Lysogenic bacteria- a bacterium that has a piece of the viral DNA embedded in it’s own DNA (has a prophage) • Prophage (provirus)- segment of viral DNA that is integrated in the host’s DNA • Cell Multiplication- host cell is dividing and dividing, all the while making copies of the viral nucleic acid • Differences between Lytic and Lysogenic Cycles: Lytic Cycle Lysogenic Cycle Viruses cause many infectious diseases • There are many examples of viral infections. – common cold Viruses cause many infectious diseases • There are many examples of viral infections. – common cold – influenza Viruses cause many infectious diseases • There are many examples of viral infections. – common cold – influenza – SARS Viruses cause many infectious diseases • There are many examples of viral infections. – HIV • The body has natural defenses against viruses. HIV-infected white blood cell Vaccines are made from weakened pathogens. • A vaccine stimulates the body’s own immune response. • Vaccines prepare the immune system for a future attack. • Vaccines are the only way to control the spread of viral disease. Immunity- achieved through the presence of antibodies Antibodies- proteins produced by the body to neutralize or destroy toxins OR disease-carrying organisms - disease-specific Antigen- any foreign substance in the body that triggers production of antibodies - Allergen, bacteria, virus etc. Types of Immunity • Active immunity • Long-lasting, sometimes life-long • Usually takes several weeks to develop • Exposure to disease organism triggers production of antibodies – Natural immunity: infection with the disease – Vaccine-induced immunity: exposure to weakened or killed form of disease organism • Passive immunity - Only lasts a few weeks or months - Protection is immediate - Person is given antibodies to a disease rather than producing them on their own o Newborn baby: from mother through placenta or breastfeeding o Blood products: receiving blood with antibodies Lytic v. Lysogenic • To complete today with your seatmate – Correctly color the lytic cycle pictures – Correctly order the lytic cycle pictures – Correctly label the lytic cycle pictures
