Portage Learning BIOD 171 Microbiology Lecture Exam Key 1-6

Portage Learning BIOD 171 Microbiology Lecture Exam Key 1-6 Exams 1. What are the two major types of nucleic acids and their roles? DNA- deoxyribonucleic acid RNA- Ribonucleic acid DNA- Cellular life has DNA and a role that DNA has is long-term storage of information, it holds the characteristics of living organisms. RNA- Is the carrier of information in form of amino acid sequence. It converts the information in the DNA and synthesizes proteins True or False: Archaea is noted for its ability to survive under harsh conditions. True. Archaea can often be found in harsh conditions such as high salt levels, high acid conditions, high temperatures and even oxygen-poor conditions. 1. Which of the following microorganisms are considered to be Eukarya? Select all that apply. A. Animalia B. Plantae C. Fungi D. Protista A,B,C,D 2. True of False: All multicellular microorganisms classified as Animalia are heterotrophic. True 3. Microorganisms classified as Plantae obtain most of their energy by converting energy into energy. Light (sunlight); chemical (sugars) 1. A defining characteristic of fungi is the presence of chitin in the cell walls. Which of following also contain chitin? Select all that apply. A. Mushrooms B. Bacteria C. Yeast D. Molds A, C and D all contain chitin. 2. True or False: A defining characteristic of Protista is the inability of colonies to form tissue layers. True. 1. Cell walls are found in which of the following (select all that apply): A. Plants B. Fungi C. Bacteria D. Mammalian cells E. Algae A, B, C, E 2. The function of the ribosome is (select all that apply): A. Lipid synthesis B. Protein synthesis C. To produce energy (ATP) D. Protein modification and distribution E. Waste disposal via hydrolytic enzymes B. Ribosomes are located in the cytoplasm of prokaryotic cells and in the ER of eukaryotic cells. 1. Identify the following cellular components by matching the number with the description. A. Cell wall B. Lysosome C. Centriole D. Rough endoplasmic reticulum E. Plasma membrane F. Nucleus G. Golgi apparatus 1 F 2 B 3 E 4 G 5 D 1. True or False: Metabolism is a controlled set of biochemical reactions that occur in living organisms in order to maintain life. True. 2. True or False: Enzymes are polysaccharides that catalyze chemical reactions. False. Enzymes are proteins that catalyze chemical reactions. 3. What are usually metal ions known to assists enzyme during the catalysis reaction? Cofactors are usually metal ions and assist enzyme during the catalysis reaction. 1. Define catabolism. Catabolism is the process of breaking down larger molecules into useful energy sources. 2. Upon cellular injury, which metabolic process is involved during the growth and repair phases of the cell? The anabolic process would be active as it (by definition) is involved in the building up of small complexes into larger complexes. 1. Describe the energy transfer process relative to both ATP and ADP. ATP has the energy (phosphate group) to donate while ADP can accept energy in the form of a phosphate group. Thus, ATP can be reduced (ATP →ADP + Pi) while ADP can be built into ATP (ADP + Pi →ATP). 2. An organism that derives its energy (generates ATP) from photons of light is called a ? Phototrophic microorganism. An organism that derives its energy by removing electrons from elemental sulfur would be classified as a ? Lithotroph 4. A reactive intermediate would be present in which phosphorylation process? A. Photophosphorylation B. Substrate-level phosphorylation C. Oxidative phosphorylation B. The chemical compound losing the phosphate group is referred to as the phosphorylated reactive intermediate. 1. The catabolism of a single molecule of glucose goes through what 3 distinct transitions? The breakdown of glucose goes through (1) Glycolysis then (2) Fermentation or Respiration and finally through (3) the electron transport chain (ETC). 2. What is the most energetic transition in the catabolism of glucose? The electron transport chain yields 34 ATP while both glycolysis and fermentation (or respiration) each yield only 2 ATP. 3. Identify the reactants of the following chemical equation: Glucose + 2NAD+ → 2 NADH + 2 Pyruvate + 2 ATP The reactants are to the left of the arrow: Glucose and 2NAD+ 4. The presence of what molecule ‘signals’ to the cell that glycolysis is about to start? Glucose-6-phosphate (G6P) 5. True or False: In the absence of oxygen fermentation produces 2 ATP. False. Fermentation only reduces NADH back to NAD+ 1. What is the primary byproduct of the TCA cycle? Select all that apply. A. NAD+ B. FAD C. NADH D. FADH2 C and D. The TCA cycle produces an abundance of reduced electron carriers (NADH and FADH2). 2. True or False. The reactants of the TCA cycle directly enter and fuel the electron transport system. False. The products of the TCA cycle (reduced electron carriers) enter and drive the production of ATP via the electron transport system. 1. In the absence of glucose, which of the following can be used as alternative energy sources? Select all that apply. A. Lactose B. Nucleic acids C. Carbohydrates D. Lipids A, C, D can all be used as alternative energy sources. 2. For the catabolism of proteins and lipids, which of the following enzymes are used? Select all that apply. A. Ligases B. Proteases C. Transferases D. Lipases B and D. Proteases breakdown proteins while lipases breakdown lipids. 3. True or False. The β-oxidation pathway catabolizes the fatty acid chains of lipids. True 1. Describe the relationship between chloroplasts and chlorophyll. Both chloroplasts and chlorophyll are associated with photosynthesis. Chloroplasts are the double membrane- enclosed organelles that contain the photosynthetic pigment chlorophyll. 2. True or False: Chloroplasts are specific to algae and plants. True 3. The process of photophosphorylation produces which of the following: select all that apply. A. ATP B. Glyceraldehyde-3-phosphate C. CO2 D. NADPH E. H2O A and D. 1. In phosphorylation, the light reactions always occur where? The process of converting light energy into chemical energy (photophosphorylation) always occurs in the membrane. 2. True or False: The Calvin cycle must occur in the absence of light. False. The term ‘dark reactions’ (also known as the Calvin Cycle) simply denotes the second stage in photosynthesis—dark reactions do not actually require darkness in order to occur. 1. How many turns (or repititions) of the Calvin Cycle are required to generate one molecule of glucose? Six. 2. Complete the following equation by placing the appropriate numbers where indicated. CO2 + ATP + NADPH + H20 → C6H12O6 + ADP + NADP+ 6 CO2 + 18 ATP + 12 NADPH + 12 H20 → C6H12O6 + 18 ADP + 12 NADP+ 1. Match the following reactions to its corresponding enzyme: 1. A-B + H2O → A-OH + B-H 2. A-B→ B-A 3. A + B → A-B 4. A-B → A + B A- Lyases B- Transferases C- Oxioreductaces D- Hydrolases E- Ligases F- Isomerases 1D 1. A-B + H2O → A-OH + B-H Hydrolases 2F 2. A-B→ B-A Isomerases 3E 3. A + B → A-B Ligases 4A 4. A-B → A + B Lyases 1. A micrometer is defined as A. 10-3 B. 10-6 C.10-9 D. 10-12 B. A micrometer is one-millionth of a meter. 2. True or False: A nanometer is longer than a micrometer. False. A nanometer is 1,000 times smaller than a micrometer. 1. Resolution and contrast are two critical factors that influence your ability to see an object. Explain each. Resolution refers to the distance between two objects at which the objects still can be seen as separate. Poor or low resolution means two (or more) objects may appear as one. Contrast is the difference in light absorbance between two objects. Poor contrast gives a high background and makes the visualization of multiple objects difficult. For instance, trying to identify 2 dark colored objects at night (low light = low contrast) versus the same 2 objects in the middle of a sunny afternoon (bright light against 2 dark objects = high contrast). 1. Assuming a fixed ocular, identify the part of the microscope you would adjust to enhance the magnification of a sample. A. Objective B. Condenser C. Iris diaphragm D. Eye piece A. Only the oculars (eyepiece) and the objectives contribute to the magnification of the sample. Since the eyepiece is fixed, only the objectives could be altered. 2. What is the total magnification (relative to your eye) of a sample imaged with a 20x objective and a 15x eyepiece? Show your math. 20 x 15 = 300x magnification 1. True or False: Staining is often required to image a cell that is adherent and flat (thin). True. Adherent, flat and unstained cells are almost invisible due to the limits on both resolution and contrast. Therefore, cell staining is often required to adequately image the sample. 2. Which of the following could NOT be seen clearly by the unaided eye? Select all that apply. A. Bacteria with diameter of 24 μm B. Protozoa with diameter of 150 μm C. Virus with a diameter of 0.2 μm D. Skin cell with diameter of 1500 μm A and C. The unaided eye can, on average, clearly resolve objects > 100 μm 1. Label the following unmarked microscope components (numbered arrows) by matching it with the components provided (letters). A. Stage B. Fine Adjustment Knob C. Iris Diaphragm D. Neck E. Condenser Lens F. Eyepiece G. Objective H. Base I. Coaxial Controls 1F 2D 3B 4G 5A 6H 1. For each of the following questions select from the list below the single best answer: Phase-Contrast Dark Field Fluorescence Confocal This type of microscope is best suited for visualizing GFP, RFP and YFP proteins. Fluorescence 2. This type of microscope can provide detailed images of live cells without staining. Phase-Contrast 3. This type of microscope is used to greatly increase the contrast between samples and background by reflecting light off of the specimen. Dark Field 4. This type of microscope is capable of capturing images in multiple focal planes, rendering a specimen in 3D Confocal 1. Identify what type of electron microscope was used to capture the following image and explain your choice. The image was captured using a Scanning Electron Microscope (SEM). The above image shows the trademark ‘shell’ image (no subcellular organelles are visible) reminiscent of SEM. Only TEM is capable of visualizing subcellular substrucutres. 1. Gram-Positive cells appear in color due to a peptidoglycan layer in the cell wall. Purple; Thick 2. Gram-Negative cells appear in color due to a peptidoglycan layer in the cell wall. Pink; Thin 1. True or False: The distinguishing characteristic of Gram-Negative bacteria is the presence of LPS in the outer membrane. True. 2. True or False: If you wish to study the motility of an organism you cannot heat fix, but you can chemically fix the specimen. False. Both heat and chemical fixation strategies will kill the cell, making motility observations impossible. 1. You want to observe the size and shape of a cell. What is the easiest staining technique that you could perform? Name at least one dye you would use during this process. Simple stain. You could use any of the following: methylene blue, crystal violet, safranin or fuschin. 2. You suspect a patient may have TB. Once a sample has been obtained it is sent off to the lab for an acid-fast stain. If the patient were infected with TB, describe what you would expect to see on the stained slide. You would expect to see red cells (TB+) on a blue background (TB negative). 3. True or False: If a patient is suspected of having malaria, a Giemsa stain would be an appropriate differential test to perform. True. Giemsa stains are often used in the clinical setting to aid in the diagnosis of blood parasites. 1. True or False: Growth media is best suited for distinguishing between two similar species of bacteria. False. Growth media is designed to simply support (and not restrict) microbial growth. 2. A researcher is asked to determine which of two vials contains E coli and which contains Salmonella. Knowing both are Gram-Negative while only one of them is capable of fermenting lactose, which type of media would be best suited: A. Growth media B. Differential media C. Selective media D. Selective and Differential media B. Differential media distinguishes between two, often related, microbes. 3. What are the requirements of a fastidious microbe? A fastidious microbe is an organism with complex growth requirements such that if absent it will not grow. Enriched medias thus contain these specific and essential nutrients required for the growth of a particular subset of microorganisms. 1. True or False: LB agar is classified as a selective, non-differential media. False. LB agar is the most basic type of agar and like LB media supports the growth of virtually all microbes without restriction. 2. What is agar used for in microbiology? Agar is used to create a solid, smooth surface on which microbes can grow. 1. Match the following hemolytic class with its description of activity. 1. Alpha hemolysis B A. No hemolytic activity 2. Beta hemolysis C B. Incomplete hemolytic activity 3. Gamma hemolysis A C. Complete hemolytic activity 1. Columbia CNA agar is most closely related to which media: A. Trypticase Soy Agar B. MacConkey Agar C. Blood agar D. EMB agar C. CNA agar is similar to BAP as it is also enriched with blood and allows for differentiation based on hemolytic patterns. 2. True or False: Chocolate agar gets its brown color from cocoa to produce an enriched media. False. Chocolate (cocoa) is never added to the media. The name is derived simply based on the color that actually comes from the presence of ‘cooked’ (lysed) red blood cells in the media. 3. A researcher is studying a strain of E. coli currently growing on a MacConkey plate. However, the researcher can’t remember if E. coli is Gram-Positive or Gram-Negative. Would a Gram stain be necessary to confirm? Why or why not? No. A Gram stain would not be necessary, as only Gram-Negative microbes will grow on MacConkey agar. Thus, E. coli is a Gram-Negative microbe. 1. In an attempt to detect the presence of the pathogenic strain of E. coli O157:H7, a researcher spread a culture onto a MacConkey agar with failed results. What type of agar should they (correctly) try next? Why? The microbe should be plated on SMAC (Sorbitol-MacConkey agar) as it is specifically formulated to detect O157:H7. Pathogenic E. coli (O157:H7) cannot ferment sorbitol while non-pathogenic E. coli can ferment both soribitol and lactose. Therefore, colonies that ferment (acidic conditions; non-pathogenic) can be differentiated from non-fermenters (neutral to basic conditions; pathogenic). 1. In Eosin Methylene Blue (EMB) agar, what color indicates the presence of E. coli? Metallic Green. 2. Which type of agar media is best suited to support the growth of Staphylococcus? A. MacConkey agar B. Blood agar C. Columbia CNA agar D. Mannitol salt agar E. Chocolate agar. D. Mannitol salt agar 1. What is the process of spreading a bacterial culture onto a petri dish? Plating. 2. Describe the primary advantage of using a petri dish over growing a liquid culture? The primary advantage is that cells are held into place. When grown in a nutrient broth, bacterial cells can multiply but are free to move around in solution. When grown on agar within a petri dish the fixed in such as way as to form colonies. 3. True or False: The visualization of colonies on a petri dish represents bacterial cells that have multiplied ~2-3 times. False. When an individual colony is visible on agar the bacterial cell has multiplied often a million times over. 1. True or False. The purpose of a quadrant streak is to produce individual colonies of a bacterial population. True. The purpose of the quadrant streak is to generate individual colonies such that a single (pure) bacterial sample can be isolated. 2. A dilution gradient is formed when carrying out what generalize plating strategy? A quadrant (aka phase-dilution) streak. The resulting gradient should always contain within it the growth of individual colonies. 3. In what phase of a dilution streak would you expect to find the highest concentration of bacteria, P2 or P4? P2 (Phase 2) would contain a higher concentration of bacteria than Phase 4 (P4). The phases rank (from highest to lowest), P1 > P2 > P3 > P4. 1. True or False. When performing a dilution streak a new (or sterilized) loop must be used for each phase. True. Failure to do so would prevent the establishment of a dilution gradient, as the same bacterial concentration would be spread across both phase regions. 2. In order to encourage growth of a slow growing microbe what might a researcher do during a phase dilution streak? A researcher may either (1) opt to perform only a 3-phase dilution streak or (2) pass the loop through the previous phase multiple times (as opposed to only once). 3. True or False. To restrict the growth of a pathogenic microbe a researcher might decrease an incubator from 37°C to 25°C. True. Pathogenic strains of bacteria tend to grow faster than non-pathogenic strains at 37°C, so researchers may set incubators at 25°C to restrict its growth. When given an unknown bacterial sample the first step is to expand the current bacterial population. Which form of media best suites this need? Why? A. MSA agar B. LB media containing ampicillin and neomycin C. MacConkey agar D. Blood agar Streptococcus would not survive in the presence of peroxides—it is unable to breakdown peroxides (catalase negative). Left unchecked, peroxides would damage the cellular integrity of Strep causing lysis/cell death. 2. Streptococcus is most often streaked onto A. Chocolate agar B. EMB agar C. Blood agar D. Spirit Blue agar C. Strep is often cultured on Blood agar plates to determine its hemolytic properties, which aids in the classification (and differentiation) process. 3. True or False. The Lancefield groups are used to subdivide antigenic groups of gamma-hemolytic Streptococcus. False. The Lancefield groupings are used to subdivide beta-hemolytic Strep. 4. Greater than 90% of all human streptococcal infections belong to: A. Group B B. Group D C. Group A D. Group C C. Group A is the causative agent behind > 90% of all Strep infections. 5. Left untreated, strep throat can progress to , which displays hemolytic activity. A. Strep. Pharyngitis; beta B. Strep. Septicemia; gamma C. Rheumatic fever; beta D. Strep. Pharyngitis; alpha C. Strep throat (also known as strep. Pharyngitis) can lead to Rheumatic fever if left untreated. Strep. Pharyngitis displays beta-hemolytic activity. 1. True or False. Under most circumstances, staphylococcus can be found in ~30% of human population where it remains pathogenic. False. While staphylococcus can be found in ~30% of the human population, it remains non-symptomatic. False. While staphylococcus can be found in ~30% of the human population, it remains non-symptomatic. 2. When a bacterium neither harms nor benefits from the host from which it obtains nutrients, it is referred to as being . Commensal. 3. In order to differential screen staphylococcus species, agar plates should contain what additive? Bile salts. Staphylococcus species are capable of growth in the presence of bile salts. 1. Match the following symptoms with their respective diseases: 1. Childhood skin disease near mouth/nose C A. Folliculitis 2. Infection of thin, transparent scleral tissue D B. Scalded-skin syndrome 3. Infection occurs at time of birth E C. Impetigo 4. Pus-filled lesions on skin or hair A D. Conjunctivitis 5. Ruptured pustules; treated with Penicillin B E. Ophthalmia Neonatorum 2. True or False. Staphylococcus is the only causative agent of conjunctivitis. False. There are bacterial (staph) and viral forms of conjunctivitis, both resulting in the inflammation of the conjunctiva and ‘pink eye.’ 2. A 5-month-old child is given honey at breakfast and begins showing symptoms consistent with botulism. Would the child’s illness be classified as foodborne, infant or wound botulism? 2. Identify the medical condition characterized by robust carbohydrate fermentation under anaerobic conditions, swelling of the infected areas and fever. Gas gangrene. The key identifier here is the robust carbohydrate fermentation, which manifests as intense gas production and swelling—both trademark conditions of gas gangrene. 3. The alpha-toxin perfringolysin is associated with which medical condition caused by Gram-positive anaerobic bacteria? A. Tetanus B. Botulism C. Gas gangrene D. Leprosy C. Gas gangrene. The bacterium that produces the alpha toxin perfringolysin is aptly named Clostridium perfringens. 1. You develop a fever, chills and pneumonia after recently returning from a getaway weekend where you sat in a hot tub. What bacterial disease would a doctor suspect is causing your symptoms? Would the doctor suspect you contracted it from another person? Legionnaires. No—legionella cannot be spread simply by direct contact between people. Legionella can only be transmitted through droplets small enough to be breathed in. 2. True or False. Pneumonic plague is often characterized by painfully swollen lymph nodes. False. Pneumonic plague targets the respiratory system while bubonic targets the lymph system. 3. Which form of the plague is the most rare? What does it target? Septicemic plague is the most rare and it targets the blood system. 1. Identify the following disease: D. Respiratory failure associated with lock-jaw E. Infertility and pelvic inflammatory disease. F. Sore throat, ocular discharge and fever 1. True or False. Because the genome is contained within an enclosed space, (much like the nucleus of a cell) viruses are classified as eukaryotic. False. Viruses are neither eukaryotic nor prokaryotic. 2. Describe the two basic components of a virus. A virus has (1) genomic material comprised of either DNA or RNA and (2) a capsid, a membrane-like protective structure that contains the genetic material, similar to the nucleus of a eukaryotic cell. 1. The envelope surrounds the of some viruses. Capsid. 2. True or False. You would expect to see a viral envelope on a virus infecting a bacterial cell. False. The overwhelming majority of animal viruses are enveloped whereas the majority of plant or bacteria- infecting viruses are not. 3. Rank the following viruses based on their size from largest to smallest: Paramyxovirus Poliovirus Smallpox virus Smallpox (~200nm) > Paramyxovirus (100-150nm) > Poliovirus (~30nm) 1. True or False: Viral replication occurs after it attaches and enters the host cell. True. The viral genome is never replicated before attachment and entry. True. The viral genome is never replicated before attachment and entry. 2. Place the following viral life cycle steps in order beginning with viral attachment and provide a description of each step. Uncoating: Release: Replication: Attachment: Entry: New infection: 3- Uncoating: the viral capsid disassembles 5-Release: New virus particles are produced and leave the cell 4-Replication: the viral genome is the ‘blueprint’ to make copies of itself 1-Attachment: viral receptors bind to host proteins on the surface of the cell 2-Entry: the virus fuses with the host membrane and enters the cell 6-New infection: newly produced viruses that left the host cell now go on to infect new cells. 1. A virus that infects bacteria is called a and contains a -side polygon capsid. Bacteriophage; 20-sided 2. True or False. Structurally, bacteriophages are similar to viruses that infect animals. False. Bacteriophages have a distinct composition and structure. 3. Identify the following components of a bacteriophage. 1-Capsid (or Head) 2-Collar 3- Tail (sheath) 4- Base plate 5-Tail fibers 1. Describe the main differences between lytic and temperate phages. Lytic bacteriophages replicate within the host bacteria until it ruptures, whereas temporate (or lysogenic) phages primarily exist in a non-replicative state that does not kill the host cell. Lytic phages replicate all viral proteins needed for the assembly of new virus particles whereas lysogenic phage genomes are integrated into the host genome but production of viral proteins is suppressed. 2. Based on the following image, would you expect the viral titer to be high or low? Why? Low. As turbidity is a function of the number of intact bacterial cells present in the media, the amount of virus contained within the above tube must be low. As the lytic cycle continues more and more bacterial cells will be destroyed, effectively clearing the media. 1. Which of the following cannot be spread via airborne particles: A. Measles B. Mumps C. Rubella D. A and B E. None of the above E. Measles, mumps and rubella can all be spread via airborne particles formed while coughing, sneezing, etc. 2. True or False. A patient infected with Rubella is considered infectious one week before and after the appearance of the trademark rash. True 3. Which of the following diseases does a linear, double-stranded DNA virus cause? A. Measles B. Mumps C. Rubella D. B and C E. None of the above E. Measles, mumps and rubella are all linear, single-stranded RNA viruses 4. What disease displays as a secondary characteristic swelling of the testes/ovaries and pancreas? Mumps. A patient infected with mumps (aka epidemic parotitis) has primary swelling in the parotid (salivary glands) located in the neck but also may have secondary swelling in the testes/ovaries and pancreas. 5. A patient diagnosed with German measles may additionally experience what disease? Select all that apply. A. Impetigo B. Conjunctivitis C. Rheumatic fever D. Influenza-like symptoms B and D. A patient may experience a combination of symptoms such as fever, flu-like symptoms (influenza), cough, conjuctivitis, and a red blotchy skin rash. 1. Describe two ways chickenpox can be spread. Chickenpox is highly contagious and can be transmitted (1) through both air-borne droplets (sneezing/coughs) or via (2) direct contact with the blisters of an infected individual. 2. True or False. The development of shingles is most often seen in an older adult population (> 60 years old). True. The most common age for VZV reactivation and shingle diagnosis tends to occur in people around 60 years of age. 3. True or False. Unlike chickenpox, the blisters that appear with shingles are localized and limited to small areas. True. While chickenpox blisters often cover the entire body, the blisters associated with shingles are localized and limited to small areas. 4. A person who has neither previously had chickenpox nor been administered the VZV vaccine is exposed to someone with an active VZV (shingles) outbreak and becomes infected. Explain why (or why not) the person will only develop shingles. The infected individual will not develop shingles, but will develop chickenpox. Unvaccinated and unexposed individuals must first develop chickenpox, as shingles is the reactivation of the dormant VZV virus from the chickenpox infection. 1. While traveling abroad, should you be worried about coming into contact with either the Variola major or Variola minor viruses? No. Both viruses are variants of smallpox and were eradicated in 1977. You would not need to worry about coming into contact with the virus. 2. What small (~30nm) single-stranded, non-enveloped RNA virus causes temporary or permanent paralysis by infiltrating (infecting) motor neurons within the spinal cord, brain stem or motor cortex? Polio, also known as poliomyelitis. 3. Described the main underlining differences between the Salk and Sabin polio vaccine. The Salk vaccine contained an inactivated form of the virus and was injected while the Sabin vaccine contained a live attenuated (weakened) form of the virus and was administered orally. 4. Which subtype of Influenza is the most virulent? Influenza A 1. A drug company is trying to develop a new drug that will inhibit viral entry of Influenza. Would the drug company target hemagglutinin proteins or neuraminidase proteins? Why? Hemagglutinin (HA) proteins would be targets as they are directly involved in viral attachment and entry into the host cell. Neuraminidase proteins are involved in the budding and release of new viral particles and would thus not be the correct target. 2. Explain why the flu shot given each year may not be 100% effective at preventing the flu? It is possible to receive a flu vaccine and yet (unfortunately) still get the flu in the same season if you are exposed to a viral strain that was not included in the vaccine. There are a large number of variants and the flu vaccine is unable to vaccinate against all subtypes. Medical researchers predict and then distribute flu vaccines based current trends and the available data relative to the most common circulating strains. Unfortunately, this model is not always 100% accurate. 1. True or False. The viral capsid of HIV is dumbbell shaped and contains ~2,000 copies of the viral protein p24. False. The HIV capsid is conical (cone) shaped. 2. The HIV surface glycoprotein gp120 binds what host cellular receptor? A. CD3 B. CXCR4 C. CCR5 D. CD4 D. HIV gp120 binds to CD4. 3. An individual infected with HIV is placed on anti-retroviral medication. Describe how the medication will affect the virus. As the name suggests, anti-retrovirals are intended to inhibit (anti) the process of reverse-transcription (retro). Once the virus enters the cell and uncoating is complete, the viral enzyme reverse transcriptase (RT) acts on the two RNA copies, creating a complementary DNA strand. Anti-retrovirals attempt to block this step. In the absence of anti-retroviral medications, the now double-stranded DNA is transported to the nucleus where it can integrate into the host genome and begin replicating. By inhibiting the process of RT, anti-retroviral medications effectively block the production of new viruses by preventing its integration and replication.