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Viruses What do you think this is? What do you Think These Objects are? Are They Living? Prion, Virus, and Viroid Viroid – pathogen causes disease in a plant. Protein but no capsid - RNA Prion – pathogen made only of a protein. Mutates your proteins! No DNA OR RNA 2. Plant Viruses(viroids) First plant virus to be identified was the tobaccomosaic virus 400 viruses that infect plants, causing as many as 1000 diseases Can be beneficial - flower color, Plant Virus Tobacco Mosiac 3. Prions: Particles composed of proteins and have no nucleic acids (still infectious) Influence how proteins fold into their active shape Example: Mad cow disease (destroys brain damage). Prions(cause mutations in chromosomes or proteins) Alzheimer's disease Creutzfeldt-Jakob disease Down's syndrome Fatal familial insomnia Gerstmann-Straussler syndrome Kuru Leprosy Prion crystalline protein structure Viroids So small; No real pictures! Viroids Hepatitis D Bacteria Vs Virus VIRUSES Virus: infectious particle that contains DNA or RNA surrounded by a protein coat that can only reproduce in a host cell. Latin for “poison”. Bacteriophage attacking a bacteria! History of viruses Martinus Beijerinck: Dutch scientist who said that disease is caused by tiny particles in juice. Called them viruses. Latin for poison. Wendall Stanley: isolated crystals of the tobacco mosic virus. Dmitri Ivanovski: for tobacco mosiac in liquids extracted from infected plants. Are viruses alive? Scientists are still arguing!!! At the boundary of life, between the macromolecules (which are not alive) and the prokaryotic cells (which are), lie the viruses and bacteriophages (phages). These twilight creatures are parasites responsible for causing many diseases in living things (herpes and HIV in humans, for example). Viruses are found everywhere. In isolation, viruses and bacteriophages show none of the expected signs of life. They do not respond to stimuli, they do not grow, they do not do any of the things we normally associate with life. Characteristics of Living Things Respond to stimulus: virus respond when a cell is near and attaches. Cells: Not cells as we know them Adapt: The viruses do mutate to become stronger but only in a host cell. Reproduces: only in a host cell Energy: Uses energy of the host DNA: Yes they do have their own Grow and develops: Only in host Viruses are parasites that can only perform certain characteristics in host cells. Host: The cell that the virus attaches and uses their DNA and resources. How do They Name Viruses 1. After the disease they cause. 2. After the organ or tissue they attack 3. Today, they are given a genus name ending in the word virus. Code numbers are given to similar viruses PARTS OF A VIRUS Viruses consist of a core of nucleic acid, either DNA or RNA, and a protective coat of protein molecules and sometimes lipids(capsid). CAPSID: Protein coat Surrounding the DNA. Why is Capsid Important? It is the protein coat around the virus that protests its DNA or RNA. IT IS WAY THEY ARE SO HARD TO KILL!!!!!! How Do Viruses Attack Their Host Host - Cell the virus attacks. Attaches to the host cell and interlocks with the protein of the host cell. Viruses are very specific to the cells they attack. This helps in the spread of the disease. The outside envelope matches the cell that it attacks. Viruses are specific! Attacking Host The virus will attach itself to the host cell. It will then shoot its DNA into the host cell. The virus is a parasite that uses the host cell for its energy and reproduction. It is a little different if it is a bacteria cell or eukaryotic cell. Attacking the host The size and shape of a virus determines which cells or host they can attack. Virus Attached to Host Size and Shape of Viruses Viruses come in all shapes sizes. You can only see them with a microscope. 3 shapes of viruses 1.Enveloped – round with spikes( flu viruses) 2.Helical – Long narrow coiled shape( rabies) 3.Polyhedral- many sides(foot and mouth disease) The different proteins that make up the capsid determines the shape of the virus. Difference between a bacteriophage and a virus Bacteriophages attack bacteria (prokaryotes) viruses attack eukaryotic cells(have a nucleus). Viruses and bacteriophages invade cells and use the host cell's machinery to synthesize more of their own macromolecules. Once inside the host the bacteriophage or virus will either go into a Lytic Cycle destroying the host cell during reproduction. or It will go into a Lysogenic Cycle - a parasitic type of partnership with the cell Lytic Cycle In the lytic cycle, the virus takes over the hosts DNA and grows its own. It grows its own DNA and new viruses. The virus uses the energy of the host cell. When it is full, the host cell explodes and releases new viruses. Lysogenic Cycle The virus COMBINES its DNA with the host DNA producing a Prophage. The cell is not destroyed. As new cells are made, it will be the virus and not host cell. Cell not destroyed. The Lytic Cycle The Lysogenic Cycle 4 types of Viruses Retroviruses Viruses that contain RNA as their nucleic acid Once inside a host cell, the retrovirus makes DNA from its RNA Use reverse transcriptase (enzyme) to do thislocated inside capsid The double-stranded DNA is then inserted into the host cell’s chromosome and becomes a provirus Example: HIV (Human Immunodeficiency Virus) infects white blood cells, which are used in fighting off infections and disease A retrovirus injects the enzyme, reverse transcriptase into the cell to copy viral RNA into DNA. HIV Virus HIV is a retrovirus injecting the enzyme, reverse transcriptase into the cell to copy viral RNA into DNA. HIV doesn’t target just any cell, it goes right for the cells that want to kill it. “Helper" T cells are HIV's primary target. These cells help direct the immune system's response to various pathogens. HIV undermines the body's ability to protect against disease by depleting T cells thus destroying the immune system. The virus can infect 10 billion cells a day, yet only 1.8 billion can be replaced daily. After many years of a constant battle, the body has insufficient numbers of T-Cells to mount an immune response against infections. At the point when the body is unable to fight off infections, a person is said to have the disease AIDS. It is not the virus or the disease that ultimately kills a person; it is the inability to fight off something as minor as the common cold. Viruses are host specific – a protein on the surface of the virus has a shape that matches a molecule in the plasma membrane of its host, allowing the virus to lock onto the host cell. How Do Vaccines Work A vaccine contains a killed or weakened part of a germ that is responsible for infection. Because the germ has been killed or weakened before it is used to make the vaccine, it can not make the person sick. When a person receives a vaccine, the body reacts by making protective substances called "antibodies". The antibodies are the body's defenders because they help to kill off the germs that enter the body. In other words, vaccines expose people safely to germs, so that they can become protected from a disease but not come down with the disease. Jenner was operating on the now widely accepted principle that once a person catches a certain disease, he or she is immune to it for the rest of their life. For example, once you've had the chickenpox, it's extremely unlikely that you'll ever catch it again. This is because your body, when exposed again, will recognize the disease and fight it off. The beauty of vaccines is that they help the body develop diseasefighting abilities without making you sick. Vaccines accomplish this amazing feat by tricking the body into believing it already has the full-blown disease. Here are the steps in this process, known as the "immune Vaccine-preventable Diseases Anthrax Cervical Cancer Diphtheria Hepatitis A Hepatitis B Haemophilus influenzae type b Human Papillomavirus Influenza Japanese encephalitis Lyme disease Measles Meningococcal Monkey pox Mumps Pneumococcal Polio Rabies Rotavirus Rubella Shingles Smallpox Tetanus Typhoid Tuberculosis Varicella Yellow Fever Common Cold Swine Flu Bird Flu Bacteria 1.Organelles 2.Kill with antibiotic 3.Reproduces on own 4.Needs energy 5. Cell 6.Responds 7.Adapts 8.Grows Virus DNA Reproduces Energy from host Mutates hard to kill Capsid