BIO 274 1st Edition Exam 2 Study Guide Chapters 13 15 Chapter 13 Viruses Viroids and Prions 1935 Wendell Stanley first studied virus Viruses o Contain a single type of nucleic acid DNA or RNA o Contain a protein coat that surrounds the nucleic acid o Multiply inside living cells by using the synthesizing machinery of cell o Cause the synthesis of specialized structures that can transfer the viral nucleic acid to other cells Most viruses infect specific types of cells of only 1 host species Bacteriophages viruses that infect bacteria Virion complete fully developed infectious viral particle composed of nucleic acid surrounded by a protein coat outside of a host cell and is a vehicle of transmission from 1 host cell to another Viruses are classified by their nucleic acid coat structure differences Capsid protein coat that protects nucleic acid of a virus o Composed of protein subunits called capsomeres o Covered by envelope which sometimes have spikes carbohydrate protein complexes that can be used to distinguish between viruses NO specific epithets for viruses Viral species group of viruses sharing the same genetic info niche human immunodeficiency virus aka HIV Cytopathic effect CPE when cells deteriorate as they multiply Bacteriophages multiply by Lytic cycle ends with the lysis death of the host cell Lysogenic cycle host cell lives OR These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute o Lytic Cycle 1 Attachment Chance collision of phage particles bacteria causes attachment adsorption 2 Penetration Bacteriophages injects its DNA into bacterium o Bacteriophage s tail releases an enzyme phage lysozyme which breaks down a portion of the bacterial cell wall 3 Biosynthesis 4 Maturation Virus degrades host DNA which stops protein synthesis growth Bacteriophage DNA and capsids are assembled into complete virions 5 Release Plasma membrane breaks open o Lysogenic Cycle Lysogenic phages can incorporate their DNA into the host cell s DNA 1 Upon penetration into cell the once linear phage DNA forms a circle that can multiple and be transcribed leading to the production of a new phage to either o Cell lysis OR o Lysogenic cycle phage integrates within bacterial chromosome by recombination becoming a prophage then lysogenic bacteria reproduces normally 3 Important Rules of Lysogeny o Lysogenic cells are immune to reinfection by the same phage o The host cell may exhibit new properties Phage conversion o Lysogeny makes specialized transduction possible Multiplication of Animals Viruses o Attachment entry uncoating release Attachment the attachment sites of animal viruses are distributed over the surface of the virus Entry many viruses enter into eukaryotic cells by receptor mediated endocytosis plasma membrane folds in to form vesicle filled with virion or by fusion viral envelope fuses with the plasma membrane releases the capsid into the cell s cytoplasm Uncoating cell digests capsid Oncogenes can be activated to abnormal functioning by a variety of agents mutagenic chemicals high energy radiation viruses 10 of cancers are virus induced Tumor cells undergo transformation to contain a virus specific antigen on their cell surface called tumor specific transplantation antigen TSTA or an antigen in their nucleus called T antigen Oncogenic viruses are found within several families of DNA containing viruses Adenoviridae Herpesviridae Poxvirida Papovaviridae and hepadnaviridae Retrovirus any of a group of RNA viruses that insert a DNA copy of their genome into the host cell in order to replicate HIV A persistent viral infection is apparently different from a latent viral infection in that in most persistent viral infections detectable infectious virus gradually builds up over a long period rather than appearing suddenly Plant cells are generally protected from disease by cell wall Viroids short pieces of naked RNA only 300 400 nucleotides long w no protein coat Chapter 14 Principles of Disease and Epidemiology Pathology is o 1st concerned with the cause or etiology of disease o 2nd it deals with pathogenesis the manner in which a disease develops o 3rd concerned with the structural and functional changes brought about by disease with their final effects on the body Infection invasion or colonization of the body by pathogenic microorganisms may exist in the absence of detectable disease Disease occurs when an infection results in a change from a state of health abnormal state in which part or all of body is not properly adjusted or incapable of performing its normal functions The Human Microbiome Project o 2007 o to analyze microbial communities called microbiomes that live in on human body o Goal determine the relationship between changes in the human microbiome human health disease Normal microbiota flora microorganisms that establish more or less permanent residence but that do not harm Transient microbiota may be present for several days weeks months then disappear Microbes are NOT essential to life but help a lot Microbial antagonism competitive exclusion the normal microbiota benefit host by preventing the overgrowth of harmful microorganisms Symbiosis relationship between 2 organisms where at least 1 organism is dependent on the other Commensalism 1 of the organism benefits other is unaffected Mutualism both organisms benefit Parasitism 1 organism benefits other is harmed Opportunistic pathogens ordinarily do not cause disease in their natural environment but may cause disease in a different environment Robert Koch studied anthrax tuberculosis made postulates 1 The same pathogen must be present in every case of the disease 2 The pathogen must be isolated form the diseased host grown in pure culture 3 The pathogen from the pure culture must cause the disease when it is inoculated into a healthy susceptible laboratory animal 4 The pathogen must be isolated from the inoculated animal must be shown to be the original organism Symptoms changes in body function these subjective changes are not apparent to observer Signs are objective changes the physician can measure observe lesions swelling fever Syndrome specific group of symptoms or signs that always accompany a particular disease Communicable disease any disease that can spread from 1 host to another either directly or indirectly Chickenpox measles genital herpes Contagious diseases disease that are easily spread from 1 person to another
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