Presentation on theme: "Viruses and Prokaryotes What Viruses Mean To You If you have ever had a cold, you are probably familiar with the word virus. It is a word that makes most."— Presentation transcript:
Viruses and Prokaryotes What Viruses Mean To You If you have ever had a cold, you are probably familiar with the word virus. It is a word that makes most people frown. Section 19-3 Go to Section: 1. What do you think of when you hear the word virus? Make a list of all the words you can think of that relate to viruses. 2. What are two things that you would like to find out about viruses?
Viruses and Prokaryotes Viruses A.What Is a Virus? B.Viral Infection 1.Lytic Infection 2.Lysogenic Infection C.Viruses and Disease 1.Viruses and Cancer 2.Retroviruses 3.Prions D.Are Viruses Alive? Section 19-3 Go to Section:
Viruses and Prokaryotes KEY CONCEPT Infections can be caused in several ways.
Viruses and Prokaryotes Section 19-3 Common Diseases Caused by Viruses Oncogenic viruses Retroviruses Adenoviruses Herpesviruses Poxviruses DNA RNA DNA cancer cancer, AIDS respiratory infections chickenpox smallpox Type of VirusNucleic AcidDisease Go to Section:
Viruses and Prokaryotes Viruses, bacteria, viroids, and prions can all cause infection. Any disease-causing agent is called a pathogen. viruses 50-200 nm prokaryotics cells 200-10,000 nm prion 2-10 nm viroids 5-150 nm eukaryotics cells 10,000-100,000 nm 100 nm 1 nanometer (nm) = one billionth of a meter
Viruses and Prokaryotes What are Viruses A virus is a non-cellular particle made up of genetic material and protein that can invade living cells.
Viruses and Prokaryotes The Structure Of a Virus (Draw the shown diagram) Viruses are composed of a core of nucleic acid The Nucleic acid core is surrounded by a protein coat called a capsid The Nucleic core is either made up of DNA or RNA but never both
Viruses and Prokaryotes A virus is made of DNA or RNA and a protein coat. –non-living pathogen –can infect many organisms A viroid is made only of single-stranded RNA. –causes disease in plants –passed through seeds or pollen
Viruses and Prokaryotes A prion is made only of proteins. –causes misfolding of other proteins –results in diseases of the brain
Viruses and Prokaryotes KEY CONCEPT Viruses exist in a variety of shapes and sizes.
Viruses and Prokaryotes Viruses differ in shape and in ways of entering host cells. Viruses have a simple structure. –genetic material –capsid, a protein shell –maybe a lipid envelope, a protective outer coat capsid nucleic acid lipid envelope surface proteins capsid nucleic acid lipid envelope Surface proteins capsid surface proteins nucleic acid helical (rabies) polyhedral (foot-and-mouth disease) enveloped (influenza)
Viruses and Prokaryotes T4 Bacteriophage Tobacco Mosaic Virus Influenza Virus Head Tail sheath DNA Tail fiber RNA Capsid Surface proteins Membrane envelope RNA Capsid proteins Section 19-3 Figure 19-13 Virus Structures Go to Section:
Viruses and Prokaryotes Viruses enter cells in various ways. colored SEM; magnifications: large photo 25,000; inset 38,000x –bacteriophages pierce host cells
13.1 Ecologists Study Relationships Escherichia Coli Bacterium E. coli is a bacterium. That is a crude cell, it is not a virus because viruses are protein containers with DNA cores or RNA cores.
13.1 Ecologists Study Relationships E. Coli and the Bacteriophage What it looks like in real life
Viruses and Prokaryotes –viruses of eukaryotes enter by endocytosis Viruses enter cells in various ways.
Viruses and Prokaryotes –viruses of eukaryotes also fuse with membrane Viruses enter cells in various ways.
Viruses and Prokaryotes host bacterium The bacterophage attaches and injects it DNA into a host bacterium. The host bacterium breaks apart, or lyses. Bacteriophages are able to infect new host cells. The viral DNA directs the host cell to produce new viral parts. The parts assemble into new bacteriophages. The viral DNA forms a circle. Viruses cause two types of infections. A lytic infection causes the host cell to burst. The virus may enter the lysogenic cycle, in which the host cell is not destroyed.
Viruses and Prokaryotes A lysogenic infection does no immediate harm. The viral DNA is called a prophage when it combines with the host cell’s DNA. Although the prophage is not active, it replicates along with the host cell’s DNA. Many cell divisions produce a colony of bacteria infected with prophage. The prophage may leave the host’s DNA and enter the lytic cycle.
Viruses and Prokaryotes KEY CONCEPT Some viral diseases can be prevented with vaccines.
Viruses and Prokaryotes Viruses cause many infectious diseases There are many examples of viral infections. –common cold
Viruses and Prokaryotes –influenza Viruses cause many infectious diseases There are many examples of viral infections. –common cold
Viruses and Prokaryotes –influenza Viruses cause many infectious diseases There are many examples of viral infections. –common cold –SARS
Viruses and Prokaryotes –HIV HIV-infected white blood cell Viruses cause many infectious diseases There are many examples of viral infections. The body has natural defenses against viruses.
Viruses and Prokaryotes Retrovirus Change DNA into RNA. Example of a Retrovirus is HIV
Viruses and Prokaryotes A typical, "minimal" retrovirus consists of: an outer envelope which was derived from the plasma membrane of its host many copies of an envelope protein embedded in the lipid bilayer of its envelope a capsid; a protein shell containing two molecules of RNA and molecules of the enzyme reverse transcriptase
Viruses and Prokaryotes Vaccines Viruses grown on chicken embryos are attenuated vaccines Another type of vaccine is made by heat killing the virus
Viruses and Prokaryotes 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.