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 viroids 5-150 nm viruses 50-200 nm prokaryotics cells 200-10,000 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) helical (rabies) polyhedral (foot-and-mouth disease) capsid nucleic acid lipid envelope surface proteins capsid surface proteins nucleic acid capsid nucleic acid lipid envelope Surface proteins
A bacteriophage is a virus that infects a bacterium. capsid DNA tail sheath tail fiber HEAD collar TAIL Base plate
Viruses enter cells in various ways. bacteriophages pierce host cells viruses of eukaryotes enter by endocytosis or fuse with the membrane
LYTIC CYCLE 6
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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 HIV-infected white blood cell The body has natural defenses against viruses.
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 Passive 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 Newborn baby: from mother through placenta or breast-feeding 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