Study objectives for the third exam
Study objectives for the third exam BIOL 455
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This 18 page Study Guide was uploaded by Kseniya Notetaker on Tuesday November 17, 2015. The Study Guide belongs to BIOL 455 at Kansas State University taught by Alina M De La Mota-Peynado in Fall 2015. Since its upload, it has received 49 views. For similar materials see General Microbiology in Biology at Kansas State University.
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Date Created: 11/17/15
1. What is a virus? Composition and general characteristics. Viruses contain a single type of nucleic acid (DNA or RNA) and a protein coat, sometimes enclosed by an envelope composed of lipids, proteins, and carbohydrates. They are obligatory intracellular parasites (meaning they require living host cells to multiply). They multiply by using the host cell synthesizing machinery to cause the synthesis of specialized elements that can transfer the viral nucleic acid to other cells. 2. What are the differences between viruses and other acellular agents, prions, viruses and viroids. Viruses infect living cells and once inside, transform the cell essentially into a factory for making more viruses. These acellular particles are composed of nucleic acid (genetic material), proteins and, in some cases, lipids as well. Viroids are smallest known agents of infectious disease. Whereas viruses are made up of nucleic acid encapsulated in protein (capsid), viroids are uniquely characterized by the absence of a capsid. Thus far, this type of acellular particle has only been identified as an infectious agent in plants. Prions are an abnormal form of a normally harmless protein that cause various fatal neurodegenerative diseases called Transmissible Spongiform Encephalopathies. Once present in the brain, prions cause normal proteins to refold into abnormal shapes, destroying neurons and eventually causing the brain to become riddled with holes. Acellular particles: * are not made of cells * cannot reproduce on their own * do not grow or undergo division * do not transform energy * lack machinery for protein synthesis * are so small that they can only be seen with an electron microscope 3. Understand host range and what factors determine it. Host range is the spectrum of host cells the virus can infect. There are viruses that can infect invertebrates, vertebrates, plants, protists, fungi, bacteria. Most viruses are able to infect specific types of cells of only one host species. The host range is determined by the virus’s requirements for its specific attachment to the host cell, and the availability within the potential host of cellular factors required for viral multiplication. 4. Describe the physical and chemical structure of both enveloped and nonenveloped viruses. How do they acquire an envelope? ENVELOPED: in some viruses, the capsid is covered by an envelope, which chemically, usually consists of some combination of lipids, proteins, and carbs. In most cases, the envelope contains proteins determined by the viral nucleic acid and materials derived from normal host cell components. Structurally, the enveloped virus consists of the nucleic acid>>Capsomeres>> Envelop>>Spikes(on some enveloped viruses). NONENVELOPED are viruses whose capsids are not covered by an envelope. The capsid protect the viruses from nuclease enzymes in biological fluids and promotes the viruses attachment to susceptible host cells. All viruses have capsids. Viruses have DNA or RNA. The DNA and RNA can be Double or Single stranded. Out of the single stranded RNA, there could be Positive sense or Negative sense. If a virus with negative sense RNA in order to replicate inside a cell the virus needs to produce a positive sense, because that can act as a template. Only positive sense can be transcribed, negative cant. 5. How are viruses classified based on their morphology, and how are they taxonomically classified. They are classified based on their capsid architecture. This has been shown by electron microscopy and xray crystallography. Morphology: Helical viruses resemble long rods, can be rigid or flexible. Viral nucleic acid is found within hollow cylindrical capsid with a helical structure. Rabies and Ebola are examples. Polyhedral Viruses are many sided viruses. Most common type is icosahedron which is a regular polyhedron with 20 triangular faces and 12 corners. Example is adenovirus and poliovirus. Enveloped viruses, are roughly spherical. Can be enveloped helical or enveloped polyhedral viruses. Influenza is an example of helical enveloped and Herpes is an example of polyhedral enveloped. Complex viruses, particularly bacterial viruses have complicated structures. Bacteriophage is an example. Some bacteriophages have capsids where additional structures are attached. Taxonomy: Genus names end in -virus, family names end in –viridae, order names end in – ales. A viral species is a group of viruses that share the same genetic information and host range. Specific epithets for viruses are not used. 6. Know and understand the different techniques to grow bacteriphages and animal viruses. Bacteriophages are viruses that infect bacteria. They can be grown in suspensions of bacteria in liquid media or in bacterial cultures on solid media. Solid media makes the plaque method for detecting and counting viruses. A sample of bacteriophage is mixed with host bacteria and melted agar and poured into petri plate with a hardened layer of agar media. The mix then solidities in a thin top layer. A number of clearings “plaques” are produced and are visible against a lawn of bacterial growth on the surface. Growing Animal viruses In living animals: mice, rabbits, guinea pigs. Animal inoculation may be used as a diagnostic procedure for identifying and isolating a virus from a clinical specimen. In embryonated eggs: convenient and inexpensive form of host for many animal viruses. Hole is drilled in the shell and viral suspension is injected into the fluid. Viral growth is shown by the death or damage of the embryo or pocks or lesions. In cell cultures: replaced embryonated eggs as preferred growth medium. Cultures are generally homogeneous collections of cells and can be propagated like bacterial cultures. Cell culture lines are made by treating a slice of animal tissue with enzymes that separate the individual cells. Cytopathic effect is cell deterioration as viruses multiply. Primary cell lines are derived from tissue slices. Diploid cell lines are from human embryos and can be maintained for 100 generations. Continuous cell lines are cancerous cells that can be maintained through indefinite number of generations. 7. Describe three techniques that can be used to identify viruses. Serological method like Western blotting is the most commonly used method of identification. Its where the virus is detected and identified by its reaction with antibodies. RFLPs (Fragment length polymorphisms) are restriction fragment length polymorphisms is a modern molecular method. PCR (polymerase chain reaction) 8. Explain and contrast lytic and lysogenic cycles. In the lytic cycle, the bacterial cell wall is ruptured and the progeny phages are released. Thus the host is destroyed. Viral DNA destroys Cell DNA, takes over cell functions and destroys the cell. The Virus replicates and produces progeny phages. There are symptoms of viral infection. Virtulant viral infection takes place. These are the steps: 1. Attachment 2. Penetration 3. Biosynthesis 4. Maturation 5. Release In the lysogenic cycle, the host remains intact and through excision the progeny is released. Viral DNA merges with Cell DNA and does not destroy the cell. The Virus does not produce progeny. There are no symptoms of viral infection. Temperate viral replication takes place. Both are the cycles describing the proliferation of bacteriophages in a host bacterial cell. 9. How does the replication cycle of DNA and RNA-containing animal viruses differ? Know examples of each. Shared processes by both DNA and RNA viruses: attachment, entry, uncoating, release. Differences are in biosynthesis ssDNA: Cellular enzyme transcribes dsDNA: Cellular enzyme transcribes viral DNA in nucleus (Ex: Parvoviridae) viral DNA in nucleus Viral enzyme transcribes viral DNA in RNA to make mRNA in cytoplasm virion, in cytoplasm (Ex: (Picornaviridae, Togaviridae) Herpesviridae, Papovaviridae, Poxviridae) RNA – strand: Viral enzyme copies viral RNA to make mRNA in cytoplasm DNA reverse transcriptase: Cellular (Rhabdoviridae) enzyme transcribes viral DNA in nucleus; reverse transcriptase copies dsRNA: Viral enzyme copies – strand RNA to make mRNA in cytoplasm mRNA to make viral DNA (Hepadnaviridae) (Reoviridae) RNA reverse transcriptase: Viral enzyme copies viral RNA to make DNA RNA + strand: Viral RNA functions as in cytoplasm, DNA moves to nucleus a template for synthesis of RNA (Retroviridae polymerase, which copies – strand DNA-containing viruses replicate in the nucleus of the host cell by using viral enzymes and synthesize their capsid and other proteins in the cytoplasm by using host cell enzymes. 10.What is an oncogene? A transformed cell? What is an oncolytic virus? Oncogenes can be activated to abnormal functioning by a variety of agents, including mutagenic chemicals, high energy radiation, and viruses. An oncogene is a kind of abnormal gene that predisposes cells to develop into cancers. Unlike normal genes, which can be turned off after being turned on, oncogenes are altered in a way that keeps them stuck in a state of constant activity. That uninterrupted action helps drive the uncontrolled growth that underlies tumors. 11.What is the relationship between viruses and cancer? Viruses can cause cancer. Oncogenic viruses are viruses capable of inducing tumors in animals. About 10% of cancers are known to be virus-induced. An outstanding feature of all oncogenic viruses is that their genetic material integrates into the host cells DNA and replicates along with the host cell’s chromosome. 12.How can we use viruses to treat cancer cells. 13.Contrast latent vs. persistent viral infections. A latent can be by a virus that can remain in equilibrium with the host and not actually produce disease for a long period of time. Virus inhabits cells but causes no damage until it is activated by a stimulus. Viruses gain access to the skin via blood. From the blood, some viruses may enter nerves where they remain latent. Persistent infections occus gradually over a long period. They are typically fatal. A number of these have been shown to be caused by conventional viruses. Like measles virus can be responsible for encephalitis that is bad. 14.How are plant viruses classified. Describe their lytic life cycle. Some plant diseases are caused by viroids which are short pieces of naked RNA 300-400 nucleotides long with no protein coat. Plants are usually protected from disease by an impermeable cell wall. They can enter through wounds or be assisted by other plant parasites like nematodes fungi and insects. Main classifications: dsDNA non enveloped ssRNA + strand non enveloped ssRNA – strand enveloped dsRNA non enveloped 15.What is the socio-economic impact of viruses? 1. Define pathology, etiology, infection, and disease. Pathology is the scientific study of disease. Etiology is the cause of disease. Infection is the invasion or colonization of the body by pathogenic microorganisms. Disease occurs when an infection results in any change from a state of health. 2. Define normal and transient microbiota. Normal microbiota are microorganisms that establish more or less permanent residence but do not produce disease under normal conditions. Transient microbiota may be present for a few days or weeks or months and then disappear. Microorganisms are not found throughout the entire human body but are localized in certain regions. 3. Compare commensalism, mutualism, and parasitism, and give an example of each. Commensalism is where one organism benefits and the other is unaffected. Mutualism is a type of symbiosis that benefits both organisms. Parasitism is where one organism benefits and the other is negatively affected. 4. Contrast normal microbiota and transient microbiota with opportunistic microorganisms. Opportunistic microorganisms ordinarily do not cause disease in their normal habitat in a healthy person but may do so in a different environment. For example, microbes that gain access through broken skin or mucous membranes can cause opportunistic infections. Or is the host is weakened or compromised by infections. 5. List Koch’s postulates The same pathogen must be present in every case of the disease The pathogen must be isolated from the diseased host and grown in pure culture The pathogen from the pure culture must cause the disease when it is inoculated into a healthy and susceptible laboratory animal The pathogen must be isolated from the inoculated animal and must be shown to be the original organism. 6. Differentiate a communicable from a noncommunicable disease. A communicable disease is any disease that spreads from one host to another either directly or indirectly and is said to be a communicable disease. Examples are chickenpox, measles, genital herpes, typhoid fever, tuberculosis. Noncommunicable disease is not spread from one host to another. These diseases are caused by microorganisms that normally inhabit the body and only occasionally produce disease or by microorganisms that reside outside the body and produce disease only when introduced into the body. Example is tetanus. 7. Categorize diseases according to frequency of occurrence, and severity. Frequency of occurrence: Incidence of a disease is the number of people in a population who develop a disease during a particular time period. The prevalence of a disease is the number of people in a population who develop a disease at a specified time regardless of when it first appeared. Sporadic disease is a disease that occurs only occasionally, like typhoid fever. Endemic disease is a disease that is constantly present in a population. Example is a common cold. Epidemic disease is if many people in a given area acquire a certain disease in a relatively short period. Flu is an example. Pandemic disease is a epidemic disease that occurs worldwide. Severity: Acute disease is one that develops rapidly but lasts only a short time. Flu is example. Chronic disease develops more slowly and the bodys reactions may be les severe but the disease is likely to continue or recur for long periods. Mono, tuberculosis and hepatitis B are examples. Subacute disease is an intermediate between acute and chronic, like sclerosing panencephalitis. Latent disease is where the causative agent remains inactive for a time but then becomes active to produce symptoms of the disease. Shingles is an example. 8. Define herd immunity. Herd immunity is when many immune people are present in a community. This is an advantage of vaccination because enough individuals in a population will be protected from a disease to prevent its rapid spread to those who are not vaccinated. 9. Identify four predisposing factors for disease. Prodisposing factor makes the body more susceptible to a disease and may alter the course of the disease. Gender can be a factor (females have more urinary tract infections, males have more pneumonia and meningitis) Other genetic aspects like carriers of diseases. Climate and weather are also factors. In temperate regions the incidence of respiratory diseases increases in winter because of everyone staying indoors. Inadequate nutrition, fatigue, age, encironment, habits, lifestyle, occupation, preesisting illiness, chemotherapy, emotional disturbances. 10.Define reservoir of infection. Reservoir of infection is a continual source of the disease organisms, and it can be either a living organism or an inanimate object that provides a pathogen with adequate conditions for survival and multiplication and an opportunity for transmission. 11.Contrast human, animal, and nonliving reservoirs, and give one example of each. Human reservoirs: human body is the principal reserboir. People harbor pathogens and transmit them directly or indirectly. People with or without signs can transmit. Carriers are important. Typhoid Mary is an example of carrier. Carriers play a big role in AIDS, diphtheria, typhoid fever, hepatitis, gonorrhea, amebic dysentery and streptococcal infections. Animal reservoirs: wild and domestic animals can have microorganisms that can cause human diseases. Diseases that can be transmitted to humans are called zoonoses. Transmission of these can occurs by direct contact with the animals, waste, contamination of food and water, air from for or hide or feathers, consuming infected animal products or by insect vectors. Non living reservoirs: two major are soil and water. Soil has fungi, can cause ringworm, systemic infections, bacteria that causes botulism, tetanus. Bacteria are found in soil where animal feces are used as fertilizer. Water has been contaminated by feces of humans and other animals for many pathogens especially ones that cause gastrointestinal diseases. Cholera, typhoid, salmonella, trichinellosis. 12.Explain three methods of disease transmission. Contact transmission: spread by direct or indirect contact or droplet transmission. Direct is direct transmission of an agent by physical contact between its source and susceptible host, no intermediate object. Most common is kissing, sexual intercourse. Also respiratory tract diseases like the cold and flu, staph, hepatitis , measles, scarlet fecer, STIs, AIDS, mono. Direct contact from animals can cause rabies and anthrax. Indirect contact happens when the agent of disease is transmitted from its reservoir to a susceptible host by means of a nonliving object. The term for that object is fomite. Examples are tissues, towels, bedding, diapers, cups, etc. Syringes can give you AIDS and hepatitis B. Droplet transmission happens through coughing sneezing, laughing or talking and travel less than 1 meter from the reservoir to the host. Examples are flu, pneumonia, pertussis. Vehicle transmission is getting disease agents by a medium like water, food, or air. Others include blood and other fluids, drugs. There are waterborne and there is food borne, and airborne. 13.Define healthcare-associated infections, and explain their importance. Nosocomial infections don’t show any 14.Define compromised host. Compromised host is one whose resistance to infection is impaired by disease, therapy, or burns. Two principal conditions can compromise the host: broken skin or mucous membranes and a suppressed immune system. 15.List several methods of disease transmission in hospitals, and explain how healthcare-associated infections can be prevented. 16.List several probable reasons for emerging infectious diseases, and name one example for each reason. Answered in review doc 17.Define epidemiology, and describe three types of epidemiologic investigations. Epidemiology is the science that studies when and where diseases occur and how they are transmitted in populations Descriptive Analytical Experimental 18.Identify the function of the CDC. What organization does the work of CDC at global scale? 19.Define the following terms: morbidity, mortality, and notifiable infectious diseases Morbidity is the incidence of specific notifiable diseases Mortality is the number of deaths from these diseases Notifiable infectious diseases are diseases for which physicians are required by law to report cases to. 1. Compare and contrast adaptive and innate immunity. From previous 2. Differentiate humoral from cellular immunity. Humoral: activation and clonal selection of effector B cells, which produce antibodies that circulate blood. Cell-mediated: activation and clonal selection of cytotoxic T cells, which identify and destroy infected cells. 3. What are the functions of cytokines, interleukins, chemokines, interferons, TNF, and hematopoietic cytokines? Cytokines=Chemical messengers interleukins= cytokins that serve as communicators b/t leukocytes(WBC) Chemokines Induce the migration of leukocytes (WBC) interferons= cytokines that protect cells from viral infections. TNF-α Promotes inflammation Hematopoietic cytokines Influence differentiation of blood stem cells 4. Define antigen, epitope, and hapten. Most antigens are either proteins or large polysaccharides. They provoke a highly specific immune response that results in production of antibodies that can recognize the antigen that made them. Epitopes are specific regions on antigens that antibodies interact with. A hapten a small molecule, not antigenic by itself, that can react with specific antibodies and elicit the formation of such antibodies when conjugated to a larger antigenic molecule, usually a protein, called in this context the carrier. Antibody production involves activation of B lymphocytes by the hapten and helper T cells by the carrier. 5. Explain antibody function, and describe the structural and chemical characteristics of antibodies. Antibodies are globulin proteins, and we use the word Immunoglobulins Ig for them. Antibodies are made in response to an antigen and can recognize and bind to the antigen. Each antibody has at least 2 identical sites that bind to epitopes, called antigen-bonding sites. The # of antigen-binding sites is called the valence of that antibody. Typical antibody monomer has 4 protein chains: two identical light chains, two identical heavy chains 6. Name one function for each of the five classes of antibodies. IgG antibodies are the most prevalent in serum; they provide naturally acquired passive immunity, neutralize bacterial toxins, participate in complement fixation, and enhance phagocytosis. IgM antibodies consist of five monomers held by a joining chain; they are involved in agglutination and complement fixation. Serum IgA antibodies are monomers; secretory IgA antibodies are dimers that protect mucosal surfaces from invasion by pathogens. IgD antibodies are on B cells; they may delete B cells that produce antibodies against self. IgE antibodies bind to mast cells and basophils and are involved in allergic reactions. 7. Compare and contrast T-dependent and T-independent antigens. T-independent antigens are antigens which can directly stimulate the B cells to produce antibody without the requirement for T cell help In general, polysaccharides are T-independent antigens. The responses to these antigens differ from the responses to other antigens. T-dependent antigens are those that do not directly stimulate the production of antibody without the help of T cells. Proteins are T-dependent antigens. 8. Differentiate plasma cell from memory cell. The main difference between plasma cells and memory cells is WHEN they are active in fighting infection. Plasma cells are immediately active in defense during the first exposure to invaders like viruses or bacteria producing antibodies (proteins that identify or neuatralize the foreign invaders). Memory cells last longer and are imprinted by the offending antigens of the invaders, and so are ready to mount a more rapid defense later, during a second exposure. 9. Describe clonal selection. Clonal selection is used negatively in the lymphoid organs. Here, the body's own epitopes are presented to the infant lymphocytes; those that react are recognized as traitors and destroyed before they (and their future cloned daughters) can leave and wreak havoc in the body. Clonal selection occurs when a B-cell is activated. When the B-cell binds with a particular antigen, it begins to clone itself. That mean the cell begins to divide and produce cells (clones) that will also recognize the same antigen. The cells that clone themselves they can become with plasma cells (they produce antibodies) or memory cells (which give us imunological memory) 10. Describe how a human can produce different antibodies. A foreign substance that invades the body is called an antigen. When an antigen is detected, several types of cells work together to recognize and respond to it. These cells trigger the B lymphocytes to produce antibodies. Antibodies and their responding antigens fit together like a key and a lock. Once the B lymphocytes have produced antibodies, these antibodies continue to exist in a person's body. If the same antigen is presented to the immune system again, the antibodies are already there to do their job. This principle forms the basis of immunizations. The immunization introduces the body to the antigen in a way that does not make a person sick, but it does allow the body to produce antibodies that will then protect that person from future attack. 11. Describe four outcomes of an antigen–antibody reaction. Agglutination: Causes antigens to clump together - more easily digested by phagocytes e.g. Opsonization: (from greek to cater) Coat bacteria with antibodies that enhance ingestion and lysis by phagocytes Neutralization: Block viruses from attaching to host receptors - can neutralize toxins in a similar manner Activation of Complement system: IgG and IgM bind and allow C1 to bind and start complement cascade. Lysis of the microbe attracts phagocytes to the site of infection 12. Differentiate T helper, T cytotoxic, and T regulatory cells. T helper cells can regonize an antigen presented on the surface of a macrophage and activate the macrophage Th17 deal with extracellular bacteria and fungi Th2 are good against Helminths T cytotoxic T regulatory cells are a subset of CD4+ T helper cells / They combat autoimmunity by suppressing T cells that escape deletion in the thymus. The protect from the immune 13. Define apoptosis. Programmed cell death 14. Define antigen-presenting cell. Antigen-presenting cell= group of immune cells that mediate the cellular immune response by processing and presenting antigens for recognition by certain lymphocytes such as T cells. Classical APCs include dendritic cells, macrophages, Langerhans cells and B cells. 15. Describe the function of natural killer cells. NK cells are known to differentiate and mature in the bone marrow, lymph node, spleen, tonsils, and thymus where they enter into the circulation. In order for NK cells to defend the body against viruses and other pathogens, recognition of an "altered self" state is thought to be involved. To control their cytotoxic activity, NK cells possess two types of surface receptors: activating receptors and inhibitory receptors. Some inhibitory receptors recognize MHC class I alleles, which could explain why NK cells kill cells possessing low levels of MHC class I molecules. NK cells are cytotoxic; small granules in their cytoplasm contain proteins such as perforin and proteases known as granzymes. Upon release in close proximity to a cell slated for killing, perforin forms pores in the cell membrane of the target cell, creating an aqueous channel through which the granzymes and associated molecules can enter, inducing either apoptosis or osmotic cell lysis. Cytokines play a crucial role in NK cell activation. As these are stress molecules released by cells upon viral infection, they serve to signal to the NK cell the presence of viral pathogens. 16. Describe the role of antibodies and natural killer cells in antibody-dependent cell-mediated cytotoxicity. antibodies can link target cells to NK cells, which then kill the targets directly by secreting toxic chemicals. killing is done by the NK cells, but is dependent on the presence of the antibody 17. Distinguish a primary from a secondary immune response. primary: body is first exposed to antigen, lymphocyte is activated. foriegn antigen presence triggers the T-helper which then follows the full process down the chain. secondary: same antigen is encountered at a later time. It is faster and of greater magnitude. body keeps memory B and T cells and has antibodies for the antigen. So the antibodies connect to the antigens preventing (or greatly delaying) the invading pathogen. 18. Contrast the four types of adaptive immunity.
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