BIOD 171 Final Exam
You go to visit a friend who has chickenpox. While visiting what are 2 things you will be sure to avoid so that you don't also become infected?
(1) You would want to be sure to keep a distance especially if your friend is coughing or sneezing as chickenpox can be transmitted through air-borne droplets (sneezing/coughs). (2) You would also be absolutely certain to avoid direct contact with the blisters of an infected individual.
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:
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 3- Uncoating: the viral capsid disassembles 4-Replication: the viral genome is the 'blueprint' to make copies of itself 5-Release: New virus particles are produced and leave the cell 6-New infection: newly produced viruses that left the host cell now go on to infect new cells.
Identify the following components of a bacteriophage.
1-Capsid 2- Collar 3- Tail 4- Base plate 5- Tail fibers
Complete the following equation by placing the appropriate numbers where indicated. __CO2 + __ATP + __NADPH + __ H20 → C6H12O6 + __ADP + __NADP+
1. 6 2. 18 3. 12 4. 12 5. 18 6. 12 6 CO2 + 18 ATP + 12 NADPH + 12 H20 --> C6H12O6 + 18 ADP + 12 NADP+
As the lead technician in the Microbiology Department's core Microscopy lab, you are given a list what different scientists would like to observe in their samples. You must match these samples with appropriate type of microscopy. 1. A slide stained with crystal violet simple stain to observe the arrangement of cells 2. The swimming motility of living microalgae cell 3. An unstained sample that cannot be visualized with bright field because microorganism absorbs very little light 4. The localization of a protein of interest under experimental conditions in a cell 5. Builds a 3-dimensional image of a cell
1. A slide stained withcrystal violet simple stain to observe the arrangement of cells: bright field 2. The swimming motility of living microalgae cell: phase contrast 3. An unstained sample that cannot be visualized with bright field because microorganism absorbs very little light: dark field 4. The localization of a proteinof interest under experimental conditions in a cell: fluorescence 5. Builds a 3-dimensional image of a cell: confocal
Match the following hemolytic class with its description of activity. 1. Alpha hemolysis 2. Beta hemolysis 3. Gamma hemolysis A. No change B. Greenish-brown color C. Distinct zone of clearing
1. Alpha hemolysis: greenish-brown color 2. Beta hemolysis: distinct zone of clearing 3. Gamma hemolysis: no change
Label the following unmarked microscope components (numbered arrows) by matching it with the components provided (letters).
1. Eyepiece 2. Neck 3. Fine adjustment knob 4. Objective 5. Stage 6. Base
Match the following diseases with their respective symptoms: 1. Folliculitis 2. Scalded-skin syndrome 3. Impetigo 4. Conjunctivitis 5. Ophthalmia neonatorum
1. Folliculitis: Pus-filled lesions on skin or hair 2. Scalded-skin syndrome: Ruptures pustules treated with penicillin 3. Impetigo: Childhood skin disease near mouth/nose 4. Conjunctivitis: Infection of thin, transparent scleral tissue 5. Ophthalmia neonatorum: Infection occurs at time of birth
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
1. Hydrolases 2. Isomerases 3. Ligases 4. Lyases
Identify the following cellular components by matching the number with the description.
1. Nucleus 2. Lysosome 3. Plasma membrane 4. Golgi apparatus 5. Rough Endoplasmic reticulum
How many different types of amino acids are available from which to make proteins?
20
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
Complete the following DNA strand, and indicate how many bonds are formed for each complementary pair: 3' GGTCATCG 5' 5' CC______AGC 3'
3' GGTCATCG 5' 5' CCAGTAGC 3' There are 2 bonds formed between A and T, and 3 bonds between G and C.
How many turns (or repititions) of the Calvin Cycle are required to generate one molecule of glucose?
6
What is the smallest biological unit of life?
A cell
When performing a quadrant streak, the sample is spread across the plate in such as way as to form what?
A dilution gradient is formed. The resulting gradient should always contain within it the growth of individual colonies.
A facultative anaerobe is a microorganism capable of growth under what conditions?
A facultative anaerobe is capable of growth under aerobic (with oxygen) and anaerobic (without oxygen) conditions.
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.
List at least 3 observations a researcher would be sure to note while assessing an unknown microbial sample.
A lab researcher would be certain to note: 1. Size and shape 2. Any observable motility 3. Gram status (positive or negative) 4. The presence of any chemical reactions 5. Changes in color localized to the organism or the surrounding media 6. Capture (or draw) images of any of the characteristics described above
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.
Which of the following are correct in order to be considered a pure culture? Select all that apply. A. Free from contaminants B. Obtained by a serial dilution method C. Obtained by pour plate serial dilution method D. Obtained by a 4-phase dilution streak method E. Long lifespan F. Single organism G. Multiple species
A. Free from contaminants B. Obtained by a serial dilution method C. Obtained by pour plate serial dilution method D. Obtained by a 4-phase dilution streak method F. Single organism
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 dephosphorylated (ATP ⟶ ADP + Pi), while ADP can be phosphorylated into ATP (ADP + Pi ⟶ ATP).
What is agar used for in microbiology?
Agar is used to create a solid, smooth surface on which microbes can grow.
Which of the following microorganisms are considered to be Eukarya? Select all that apply. A. Animalia B. Plantae C. Fungi D. Protista
All of the above (Animalia, plantae, fungi, and protista)
Define an essential amino acid.
An essential amino acid cannot be produced by the human body and as such must be take in from the environment through alternative sources (i.e) food.
Define anabolism.
Anabolism is the process of building up or biosynthesis of macromolecules from small molecular units into much larger complexes.
Name one substance capable of chemically fixing cells to a slide.
Any of the following are true: Paraformaldehyde, ethanol or methanol.
An individual infected with HIV is placed on anti-retroviral medication. What is the general purpose of this medication?
As the name suggests, anti-retrovirals are intended to inhibit (anti) the life cycle of retroviruses (retro). By inhibiting steps in the HIV's lifecycle, anti-retroviral medications effectively block the production of new virus particles and lower the viral load of the patient.
The plasma membrane (select all that are true): A. Only restricts movement of materials into the cell B. Is often a bilayer comprised of lipids C. Cannot prevent essential nutrients from escaping D. Contains hydrophobic tails pointing inward
B. Is often a bilayer comprised of lipids D. Contains hydrophobic tails pointing inward
Which of the following could be seen clearly by the unaided eye? Select all that apply. A. Skin cell with diameter of 1500 μm B. Protozoa with diameter of 150 μm C. Virus with a diameter of 0.2 μm D. Bacteria with diameter of 24 μm
B. Protozoa with diameter of 150 μm D. Bacteria with diameter of 24 μm (The unaided eye can, on average, clearly resolve objects > 100 μm.)
A virus that infects bacteria is called a ____ and contains a ____ -sided polygon capsid.
Bacteriophage; 20
Rheumatic fever displays ______ hemolytic activity and occurs when _______ is left untreated.
Beta; Strep. Pharyngitis (Strep throat (also known as strep. Pharyngitis) can lead to Rheumatic fever if left untreated and displays beta-hemolytic activity.)
Streptococcus is most often streaked onto: A. Blood agar B. Spirit Blue agar C. Chocolate agar D. EMB agar
Blood agar (Strep is often cultured on Blood agar plates to determine its hemolytic properties, which aids in the classification (and differentiation) process.)
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? 1. MSA agar 2. LB media containing ampicillin and neomycin 3. MacConkey agar 4. Blood agar
Blood agar. All other options (1, 2 and 3) are all forms of selective media, meaning they may potentially inhibit the growth of the unknown sample. Although blood agar is considered a differential media, it is, most importantly, a non-selective media. Given the alternatives, this is the best option.
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.
What is true pertaining to the light reactions of photosynthesis? Select all that apply. A. It is the second step of photosynthesis B. Results in the formation of NADP and ADP C. Process results in a proton concentration gradient D. It is known as the Calvin cycle E. It is the first step of photosynthesis F. Results in the formation of carbohydrates G. Process results in carbon fixation H. Results in the formation of ATP and NADPH I. Occurs in the membrane J. It converts light energy into chemical energy K. Does not depend on sunlight L. It is known as photophosphorylation
C. Process results in a proton concentration gradient E. It is the first step of photosynthesis H. Results in the formation of ATP and NADPH I. Occurs in the membrane J. It converts light energy into chemical energy L. It is known as photophosphorylation
The HIV surface glycoprotein gp120 binds what host cellular receptor?
CD4
The process of carbon fixation begins with which of the following reactants? Select all that apply. A. CO2 B. H2O C. Glyceraldehyde-3-phosphate D. ATP E. NADPH
CO2, H2O, ATP, NADPH (Carbon fixation uses the ATP/NADPH produced during light reactions to convert CO2 and H2O into useful sources of energy (carbohydrates.))
Carbon, hydrogen, and oxygen atoms come together to form what primary macromolecule? Give an example.
Carbohydrates. Any sugar is acceptable: Glucose, sucrose, fructose, galactose, lactose, maltose, etc. Also options: Starch, glycogen, cellulose, or chitin
In order to convert proteins into amino acids which metabolic process would be active?
Catabolism would be active as proteins are made up of amino acids. Therefore the process described (proteins into amino acids) is the breakdown, or catabolism of protein.
The combination of the cell membrane and the outer membrane is referred to as the (select all that apply): A. Cell wall B. Capsid C. Cell envelope D. Outer leaflet
Cell envelope The cell wall is also know as the 'outer membrane' and does not apply. A capsid is relative to a virus. The outer leaflet is only a partial description of the cell membrane.
From what source do chemotrophs acquire energy?
Chemotrophs acquire energy from preformed chemicals found in the environment.
Describe the symptoms and treatment regimen for someone infected with Clostridium perfringens.
Clostridium perfringens (also known as Gas gangrene) presents with muscle necrosis, swelling of infected areas, fever and intense gas production. Treatment entails removal of all infected tissue, often resulting in amputation of the affected areas, in conjunction with heavy antibiotic therapies.
What is the term for metal ions that assist enzymes during the catalysis reaction?
Cofactors are usually metal ions and assist enzymes during the catalysis reactions.
This type of microscope uses neither halogen nor UV light sources but rather lasers to illuminate stained cells in high resolution. A. Phase-Contrast B. Fluorescence C. Dark Field D. Confocal
Confocal
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
Conjunctivitis and influenza-like symptoms (A patient may experience a combination of symptoms such as fever, flu-like symptoms (influenza), cough, conjuctivitis, and a red blotchy skin rash.)
This type of microscope is used to greatly increase the contrast between samples and background by reflecting light off of the specimen. A. Phase-Contrast B. Confocal C. Dark Field D. Fluorescence
Dark field
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.Differential media B. Selective media C. Growth media D. Non-selective and non-differential media
Differential media
Gonnorrhea is caused by: A. Diplococcic bacteria B. Staphylococcus bacteria C. Gram-Negative spirochete D. RNA virus
Diplococcic bacteria
Which of the following can be spread via airborne particles: A. Measles B. Mumps C. Rubella D. A and B E. All of the above
E. All of the above (Measles, mumps and rubella can all be spread via airborne particles formed while coughing, sneezing, etc.)
Blood agar is which type of medium? Select all that apply. A. Selective and Differential B. Enriched C. Differential D. Selective
Enriched and differential (Blood agar can be used to differentiate between species based on its hemolytic activity.)
The ________ surrounds the capsid of some viruses.
Envelope
Match the step of infection to its description. 1. Entry 2. Evasion 3. Attachment A. Pathogen uses antigen mimicry to avoid host immune cells B. Adhesin factors are used to bind to a particular host tissue C. Mucus membranes are used to gain access to a host's tissues.
Evasion: Pathogen uses antigen mimicry to avoid host immune cells Attachment: Adhesin factors are used to bind to a particular host tissue Entry: Mucus membranes are used to gain access to a host's tissues.
True or False: A nanometer (10-9) is longer than a micrometer (10-6).
False (A nanometer is 1,000 times smaller than a micrometer.)
True or False. A patient infected with rubella is only considered infectious when the trademark rash is visible.
False (A patient infected with Rubella is infectious one week before and one week after the appearance of the rash.)
True or False: A cell that is adherent, flat (thin), and unstained is easily identified using bright field microscopy.
False (Adherent, flat cells are almost invisible due to the limits on both resolution and contrast.)
True or False. Chlyamida is an obligate parasite and as such can be grown on agar plates alone.
False (An obligate parasite requires a host (viable cells) to be present for its growth.)
True or False: Archaea, a eukaryotic class of microorganisms, is capable of surviving harsh environments.
False (Archaea are prokaryotic bacteria capable of surviving harsh environments).
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.)
True or False: Enzymes slow down chemical reactions to conserve energy.
False (Enzymes catalyze (speed up) chemical reactions).
True or False: Eukaryotic cells do not have a nucleus.
False (Eukaryotic cells do have a nucleus (prokaryotic cells do not)).
True or False. You would expect to see a viral envelope on a virus infecting a bacterial cell.
False (False. The overwhelming majority of animal viruses are enveloped whereas the majority of plant or bacteria-infecting viruses are not.)
True or False: In the absence of oxygen fermentation produces 2 ATP.
False (Fermentation only reduces NADH back to NAD+.)
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.)
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.)
True or False: As movement requires energy, metabolism can be defined as a controlled set of biochemical reactions that occur in only motile organisms in order to maintain life.
False (Metabolism occurs in all living organisms, not just those that move).
True or False. Tuberculosis is best identified by a Gram stain.
False (Mycobacterium show poor Gram staining and should be screened via an acid-fast stain.)
True or False. Under most circumstances, staphylococcus can be found in ~80% of human population where it remains non-symptomatic.
False (Staphylococcus in only found (non-symptomatic) in ~30% of the human population.)
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.)
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.)
True or False. The purpose of a quadrant streak is to expand a bacterial population.
False (The purpose of the quadrant streak is to generate individual colonies such that a single (pure) bacterial sample can be isolated.)
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.)
True or False: Highly infectious viruses undergo genome replication prior to viral attachment and entry.
False (The viral genome is never replicated before attachment and entry regardless of its level of infectivity.)
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.')
True/False. A virus is considered a microorganism.
False (Viruses are not living and as such are not considered microorganisms. Viruses can, however, be classified as microbes, a more general term that includes microorganisms and viruses.)
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.)
This type of microscope utilizes ultraviolet (UV) light to illuminate stained objects. A. Phase-Contrast B. Confocal C. Fluorescence D. Dark Field
Fluorescence
While visiting his grandparents, a 10-year-old child has green beans for dinner that were harvested from his grandparents' garden and canned the previous year. Severe illness sets in and the child is taken to the hospital. Botulism is suspected, but what form - foodborne, infant, or wound botulism? Explain why it would NOT be classified as the other two options.
Foodborne botulism. The child is too old (> 6 months) to be considered for infant botulism and wounds were not present. The green beans were likely improperly canned and under the low-acidic, anaerobic conditions, bacterial growth was encouraged.
The alpha-toxin perfringolysin is associated with which medical condition caused by Gram-positive anaerobic bacteria?
Gas gangrene (The bacterium that produces the alpha toxin perfringolysin is aptly named Clostridium perfringens.)
What are the main two roles of glucose-6-phosphate in the cell?
Glucose-6-phosphate, also known as G6P (1) prevents glucose from diffusing out of the cell as well as (2) serves as the signal molecule to the cell that glycolysis is about to begin
Match the following diseases with their respective symptoms if left untreated: 1. Gonorrhea 2. Syphilis 3. Chlamydia A. Paralysis, blindness and dementia B. Painfully swollen lymph nodes C. Cardiac and neurological complications D. Respiratory failure associated with lock-jaw E. Infertility and pelvic inflammatory disease. F. Sore throat, ocular discharge and fever
Gonorrhea: Cardiac and neurological complications Syphilis: Paralysis, blindness and dementia Chlamydia: Infertility and pelvic inflammatory disease.
Columbia CNA agar is used to isolate: A. Gram-Positive B. Mycobacteria C. Gram-Negative D. Gram-positive and Gram-negative
Gram-Positive (CNA agar restricts Gram-Negative microbes therefore only Gram-Positive microbes will grow.)
Greater than 90% of all human streptococcal infections belong to:
Group A (Group A is the causative agent behind > 90% of all Strep infections.)
Identify the disease based on the following (select all that apply): It is a small, acid-fast rod usually remaining asymptomatic for up to 20 years. It affects the skin, nerves, upper respiratory tract, and eyes of infected individuals. A. Scalded-skin syndrome B. Hansen's disease C. Bacterial conjunctivitis D. Leprosy E. Tuberculosis
Hansen's disease and Leprosy (B and D. Hansen's disease is simply another name for Leprosy. Leprosy is characterized by its ability to remain dormant for up to 20 years as well as the effects observed relative to the patients skin, nerves, lungs and eyes.)
Which subtype of Influenza is the most virulent?
Influenza A
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.
You develop a fever, chills, and pneumonia after recently using a warm midst vaporizer in an attempt to open your sinuses. What bacterial disease would a doctor suspect is causing your symptoms? Would the doctor suspect you contracted it from touching (potentially) contaminated doorknobs?
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.
For the catabolism of proteins and lipids, which of the following enzymes are used? Select all that apply. A. Lipases B. Transferases C. Ligases D. Proteases
Lipases and proteases (Proteases breakdown proteins while lipases breakdown lipids.)
An organism that derives its energy by removing electrons from elemental sulfur would be classified as a __________?
Lithotroph
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.
Identify the following disease:
Lyme disease (Lyme disease. The trademark 'bulls-eye' rash is a clear indicator.)
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.
In Eosin Methylene Blue (EMB) agar, what color indicates the presence of E. coli?
Metallic green
What disease is best characterized by painful swelling of the paratoid?
Mumps. A patient infected with mumps (aka epidemic paratitis) has swelling in the paratoid (salivary glands) located in the neck.
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
Mushrooms, yeast, and molds
What is the primary byproduct of the TCA cycle? Select all that apply. A. NAD+ B. NADH C. FADH2 D. FAD
NADH and FADH2 (The TCA cycle produces an abundance of reduced electron carriers (NADH and FADH2.))
A drug company is trying to develop a new drug that will inhibit the release of newly produced viral particles. Would the drug company target hemagglutinin proteins or neuraminidase proteins? Why?
Neuraminidase (N) proteins are directly involved in the budding and release of new viral particles and would thus be the correct target. Hemagglutinin (HA) proteins would not be advisable targets as they are directly involved in viral attachment and entry into the host cell.
A simple stain has been attempted on an unknown sample with no success. Given this property, which stain should be attempted next? A. Giemsa B. Nigrosin C.Safranin D. Acid-fast staining
Nigrosin
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.
While traveling abroad, should you be worried about coming into contact with either the Variola major or Variola minorviruses?
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.
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
None of the above (Measles, mumps and rubella are all linear, single-stranded RNA viruses.)
In the absence of glucose, which of the following cannot be used as alternative energy sources? Select all that apply. A. Lactose B. Nucleic acids C. Carbohydrates D. Fatty acid chains
Nucleic acids
Assuming a fixed ocular, identify the part of the microscope you would adjust to enhance the magnification of a sample. A. Eyepiece B. Condenser C. Objective D. Iris diaphragm
Objective (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.)
This phosphorylation process occurs in the mitochondria of chemotropic eukaryotes. A. Substrate-level phosphorylation B. Photophosphorylation C. Oxidative phosphorylation
Oxidative phosphorylation
In what phase of a dilution streak would you expect to find the lowest concentration of bacteria, P2 or P4?
P4 (Phase 4) would contain the lowest concentration of bacteria. The phases rank (from highest to lowest), P1 > P2 > P3 > P4.
Select the type of microscopy used to generate the image: A. Fluorescence microscopy B. Bright field C. Confocal D. Phase contrast microscopy E. Dark field microscopy
Phase contrast microscopy
This type of microscope can provide detailed images of live cells without staining. A. Confocal B. Dark Field C. Fluorescence D. Phase-contrast
Phase-contrast
Gram-Negative cells appear ____ in color due to a ____ peptidoglycan layer in the cell wall.
Pink; thin
Microorganisms classified as _________ obtain most of their energy by converting light energy into chemical energy.
Plantae
What is the process of spreading a bacterial culture onto a petri dish called?
Plating
Which form of the plague is highly virulent? What does it target?
Pneumonic plague is highly virulent and targets the respiratory (lungs) system.
What small (~30nm) single-stranded, non-enveloped RNA virus targets the CNS (central nervous system), causing potentially catastrophic damage to motor neurons?
Polio
The function of the Golgi 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
Protein modification and distribution (Within the Golgi complex, proteins are modified and then distributed throughout the cell).
What are the four main types of macromolecules found in cells?
Proteins, Lipids, Nucleic Acids, Carbohydrates
Gram-Positive cells appear ____ in color due to a ____ peptidoglycan layer in the cell wall.
Purple; thick
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).
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.
As Streptococcus is catalase negative would it thrive or die in the presence of peroxides? Why?
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.
Describe 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.
Identify what type of electron microscope was used to capture the following image and explain your choice.
The above image is captured via a Transmission Electron Microscope (TEM). Even at 20nm resolution (inset image), subcellular substructures are still visible. The image lacks the outside 'shell' only appearance of SEM.
Define commensal bacteria.
The bacterium neither harms nor benefits from the host from which it obtains nutrients.
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).
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.
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.
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.
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? Based upon what you know about the formulation of differential plates, explain why you chose this specific agar.
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).
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.
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+
What are the two major types of nucleic acids and their roles?
There are two major types of nucleic acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Nucleic acids are chemical molecules that carry genetic information within the cell. DNA contains a vast amount of hereditary information and is responsible for the inheritable characteristics of living organisms. RNA is responsible for deciphering the hereditary information in DNA and using it to synthesize proteins.
True of False. All multicellular microorganisms classified as Animalia are heterotrophic.
True
True or False. Although viruses may contain their genome within an enclosed space (much like the nucleus of a cell), it is considered neither eukaryotic nor prokaryotic.
True
True or False. Bubonic plague is often characterized by painfully swollen lymph nodes.
True
True or False. Structurally, bacteriophages are distinct from viruses that infect plant or animal cells.
True
True or False. The β-oxidation pathway catabolizes the fatty acid chains of lipids.
True
True or False: A defining characteristic of Protista is the inability of colonies to form tissue layers.
True
True or False: Chloroplasts are specific to algae and plants.
True
True or False: Prokaryotic cells can be subdivided into Bacteria and Archaea.
True
True or False: The distinguishing characteristic of Gram-Negative bacteria is the presence of LPS in the outer membrane.
True
True/False: (If false make true) The number of phases (3 or 4) and/or the number of times a loop passes through a previous phase (once vs multiple times) is acceptable provided it contains the growth of individual colonies.
True
True or False. There are currently no cures for tetanus.
True (Although the symptoms can be treated it is only to manage the discomfort not to cure.)
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.)
True or False: A Giemsa stain can be used to determine the presence of pathogenic bacteria.
True (Pathogenic bacteria would appear pink while non-pathogenic bacteria would appear purple.)
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.)
True or False. Although TB must be inhaled and reside in the lung in order to cause infection, TB can also spread to the brain, spine, and kidneys.
True (TB can move systemically through the blood to infect other areas (brain, spine and kidney). However, when located outside of the lung, TB tends to be non-infectious.)
True or False. The products of the TCA cycle enter and fuel the electron transport system.
True (The high volume production of reduced electron carriers from the TCA cycle is used by the ETC to drive ATP production.)
True or False. Only directly ingesting the pre-formed clostridium toxin (neither the bacteria nor its spores) will cause disease in adults.
True (The mature (adult) microbiota is capable of killing the bacteria/spores.)
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.)
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.)
Define the concept of universal precautions.
Universal precautions means any and all samples, whether known or unknown, are to be treated as potentially hazardous (or pathogenic) materials.
Rank the following viruses based on their size from largest to smallest: Orthomyxovirus Poliovirus Variolavirus
Variolavirus (~200nm) > Orthomyxovirus (100-150nm) > Poliovirus (~30nm)
The function of the lysosome 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
Waste disposal via hydrolytic enzymes (Lysosomes are membrane-enclosed organelles capable of degrading unwanted cellular debris).
Mannitol salt agar will turn what color in the presence of the pathogenic strain Staphylococcus aureus?
Yellow (Pathogenic Staph aureus will turn the agar from red to yellow.)
While observing an unknown sample of limited amounts, a researcher must determine the following observations: (1) the presence of any motility and (2) its Gram status using the same sample—the liquid sample cannot be divided. Which would you determine first and why?
You must determine motility before determining the Gram status. Motility requires a wet mount, while Gram staining requires heat fixing the sample. If one were to begin with the Gram stain the heat fixation process would kill the organism, making any observations regarding motility impossible. The correct approach would be to place the liquid culture on a glass slide and determine its motility status. Next, the same liquid culture can be heat fixed and Gram stained.
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).