66 minute read
Using Fluorescent Antibody Methods
on a plate and then serum hopefully containing antibodies is mixed with the antigen. Then the complex is detected through fluorescence or a chromogen reaction.
Low concentrations of antibodies or antigens can be detected using immunofiltration techniques. This basically filters a large volume of fluid through a porous pad. The antigen or antibody can be captured. This has been adapted for strip testing that can be used in a clinic. Testing for TORCH infections can be done with this type of testing. Pregnancy tests done at home are strip testing, also called lateral flow testing. In such cases, urine is allowed to adhere to an absorbent pad. This hydrates the dried reagents and, if antigens are present, a stripe will form.
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USING FLUORESCENT ANTIBODY METHODS
Fluorescent antibody techniques can be used by attaching a fluorescent marker to the constant region of a specific antibody. Cells can also be labeled with fluorescent antibodies in related testing. In direct fluorescent antibody testing a monoclonal antibody is bound to a fluorescent label. This is done to test for Group A streptococcus in a throat swab and to detect Mycoplasma infections and Legionella infections. Fluorescent antibodies bind to the bacteria so they can be detected on a slide.
Indirect fluorescent antibody testing looks instead for antibodies in patient’s serum. It is used to check for syphilis. Syphilis organisms are prepared from a laboratory animal that are smeared on a glass slide. If the antibodies are present, they won’t wash off the slide and, when a secondary antibody is added that has a fluorogen added to it, there will be fluorescent bacteria seen on a slide. This is a confirmatory test to the VDRL test for syphilis.
A related test is the fluorescent ANA test, which detects antinuclear antibodies. This is a test for autoimmune diseases and will be generally positive in a variety of autoimmune diseases. In order for it to work, the cells must be permeable to the anti-DNA antibody. It checks for the presence of anti-nuclear antibodies in the patient’s serum. The results are determined as a titer.
Flow cytometry can be combined with fluorescence in order to count cells that pass through an automated, cell-counting system that will specifically detect fluorescing cells.
It can be used to count the number of helper T cells in patients who have HIV disease. Cells are mixed with fluorescing antibodies and then are counted as they pass through a narrow tube. This allows for specific counting of the number of cells present in the sample.
KEY TAKEAWAYS
• There are ways to make polyclonal and monoclonal antibodies in animals or in plants.
• There are tests that can detect antigens and antibodies that precipitate in solution.
• Flocculation is a way of detecting antigens that are lipid-soluble.
• Agglutination tests will allow for agglutination of organisms or cells.
• Enzymes that change color or fluorescent tagging can be used to detect antigen and antibody complexes.
QUIZ
1. What feature of an antibody and antigen complex makes for the least chance of cross-reactivity?
a. Low affinity and low avidity b. Low affinity and high avidity c. High affinity and low avidity d. High affinity and high avidity
Answer: d. Affinity is the match between an antigen and antibody and avidity is the strength of their attachment. A complex that his high affinity and high avidity will have the least chance of cross-reactivity with another antigen.
2. What is the advantage of giving an adjuvant to an animal when an antiserum is desired?
a. It increases the affinity maturation for the antigen. b. It generally heightens the immune response. c. It prevents IgM antibodies from being made. d. It leads to a faster production of memory B cells.
Answer: b. An adjuvant is given along with an antigen when an antiserum is desired because it generally heightens the immune response in the animal being injected.
3. What is true of tests that are done as screening tests for the presence of an antibody?
a. They have high sensitivity but low specificity. b. They have high sensitivity and high specificity. c. They have low sensitivity but high specificity. d. They have low sensitivity and low specificity.
Answer: a. The ideal test has both high sensitivity and high specificity but, in reality antibody test are highly sensitive but have low specificity because of the problem of cross-reactivity to other antigens.
4. In the laboratory setting, what is the purpose of using a hybridoma?
a. To get the strongest polyclonal antibody response. b. To have a ready supply of antibodies when needed for diagnostic purposes. c. To proliferate independently, making cells that make just one antibody. d. To inject into the animal for a more specific antibody response.
Answer: c. Hybridoma cells are a hybrid of B cells and myeloma cells. They proliferate independently to make cells that, when selected properly, will just make a single antibody.
5. What is the advantage of making plantibodies rather than animal-derived monoclonal antibodies?
a. Plantibodies tend to be more specific for pathogens than animal antibodies. b. Plantibodies will treat toxin-related diseases, which can’t be done with animal antibodies. c. Plantibodies can be made in larger numbers than animal antibodies. d. Plantibody making is much cheaper and easier to make than animal antibodies.
Answer: d. Plantibodies involve a hybrid of plant and human antibodies. They are easier to grow than tissue cultures and represent a much cheaper process overall.
6. What two things are combined to make a precipitin?
a. A monoclonal antibody and a soluble antigen b. A polyclonal antibody and soluble antigens c. Two related monoclonal antibodies d. Solid antigens and a monoclonal antibody
Answer: b. In a precipitin reaction, the best precipitate forms when a soluble antigen is mixed with a polyclonal antibody, which together form a lattice that can be seen with the naked eye.
7. What does the precipitin ring test test for?
a. The antibody titer in the patient’s serum b. The concentration of an antigen in a solution c. The concentration of antibodies in a certain volume of serum d. The presence or absence of an antigen-antibody complex in a patient’s serum
Answer: a. These tests will detect a certain antibody titer in the patient’s serum but they will not detect the absolute concentration of the antibodies.
8. What type of pathogen or infection is detected in a neutralization assay?
a. Intracellular pathogens b. Lipid-related antigens c. Viruses d. Parasites
Answer: c. Neutralization reactions will detect the presence of viruses that will be neutralized by the presence of the proper antibody.
9. What is the main diseases or disease type that is detected with an immunoelectrophoresis assay?
a. Syphilis b. Multiple myeloma c. Viral infections d. Cancer
Answer: b. Multiple myeloma is a cancerous disease that allows for the making of too many monoclonal antibodies, which can be detected with an IEP assay.
10. What type of test is involved in blood typing for ABO antigens?
a. Precipitin b. Flocculation c. Immunoassay d. Agglutination
Answer: d. Agglutination testing is done by agglutinating red blood cells to see what cells agglutinate and which cells do not agglutinate.
SUMMARY
The purpose of this course has been to introduce the college-level student to the science of living things on a small scale or the field of microbiology. As you have learned, microbiology touches on many related topics, including the biochemistry of living things, the different features of cells, pathogens, and the immune system. Hopefully, you have come to understand the biochemistry involved in living structures and to know how organic molecules combine to make living things. Molecular genetics is also important and involves the structure and function of DNA and RNA, as well as how they are made and participate in protein synthesis. Pathogens, such as bacteria, viruses, and fungal organisms, cause human diseases and activate the immune system, which was also covered in detail during this course.
Chapter one in the course introduced the topic of microbiology by first covering the different types of microorganism you might uncover in your quest to understand the fundamentals of this subject. In the laboratory setting, you may have to learn the different staining techniques involved in the identification of microbes, so this was discussed. There are different types of microscopy used to study pathogens and other microorganisms, including light microscopy, dark field microscopy, and electron microscopy—each of which was covered as part of the chapter.
Chapter two started with a discussion of the origins of cell theory as well as the different historical aspects of how cells are viewed today. The two types of cells had been introduced in chapter one and these were further expanded upon in this chapter. Features that make prokaryotic cells unique and things that define what results in a cell being called eukaryotic were also covered in this chapter.
Chapter three in the course involved the study of acellular pathogens, which mainly involves viruses. Viruses may or may not be pathogenic and do not have the capability of surviving outside of a cell. There are viruses that can infect all forms of life. The life cycle of viruses was discussed in the chapter along with the ways that viruses are cultured and isolated. There are other acellular pathogens less complex than viruses that were talked about in the chapter, including viroids, virusoids, and prions.
The topic of chapter four was prokaryotic cells. There are features of prokaryotic habitats and their microbiomes you need to know about, so this was discussed. In addition, prokaryotes are
divided into bacteria and archaea. The different type of bacteria, such as proteobacteria, Gramnegative bacteria, Gram-positive bacteria, and photobacteria were discussed in this chapter. The different features that describe the Archaea domain were also covered as part of the chapter.
While there are many different kinds of eukaryotes, chapter five in the course focused mainly on eukaryotic cells that qualify as microorganisms. These include unicellular pathogens that are also eukaryotic like protists, helminths, and fungi. Algae and lichens are not pathogenic but are still important microbiological organisms that were covered in this chapter.
Chapter six taught you the biochemistry you needed to know in order to study microbiology. All living things are basically made structurally of organic molecules and the interactions between the molecules is strictly biochemical in nature. For this reason, you needed to understand what the different organic molecules are in living things. Nucleic acids are studied in another chapter but carbohydrates, lipids, and proteins were part of this chapter. The way biochemistry helps in understanding microbiology was also covered in the chapter.
Chapter seven in the course talked about cellular metabolism, which is how microbial organisms get their cellular energy. Most of this involves catabolism, which is the breakdown of certain molecules. How cells catabolize carbohydrates, lipids, and proteins was discussed in this chapter. Some organisms derive their energy from the sun. This is called photosynthesis, which was a part of this chapter. Finally, biogeochemical cycles are important to the environment so these were explained in the chapter.
The focus of chapter eight in was the genome of the cell. Cellular organisms generally have DNA making up their genome. Both DNA and RNA are nucleic acids, which are important in the genetic functioning of the cell. The structure and function of DNA and RNA were covered as part of the chapter. The totality of the DNA in a cell is referred to as the genome. The different characteristics of a cell’s genome were also discussed in this chapter. Chapter nine in the course expanded on the study of DNA by looking into microbial genetics. The ways in which DNA is replicated, the transcription process, and the processes involved in protein synthesis were covered in the chapter. Other things discussed were genetic mutations and the different ways genes are regulated. How each of these things leads to genetic diversity in prokaryotes was also discussed in the chapter.
Chapter ten touched on aspects of laboratory microbiology by looking into microbial growth. The different patterns of microbial binary fission and bacterial growth in cultures is important to understand as a laboratory microbiologist. There are certain factors that increase or decrease
microbial growth, which were covered in the chapter, along with the different physical and chemical methods of controlling microbial growth both in culture and in the environment.
Chapter eleven in the course focused on the different antimicrobial agents used to treat infectious diseases. There are different classifications of antimicrobial agents, some being bacteriostatic and some being bactericidal. There are antibiotics, antifungals, and antivirals, which were covered in this chapter. The public and medical professionals face serious challenges with regard to antibiotic and drug resistances. Some of these challenges were discussed as part of this chapter.
The focuses of chapter twelve were pathogenicity, infectious diseases, and epidemiology of infections. The basic definition of an infectious disease was explained as well as what defines a pathogen. There are specific virulence factors that identify viruses, prokaryotes, and some eukaryotes as being pathogenic in nature, which were discussed. The study of epidemiology as it applies to tracking infectious diseases was also covered in this chapter.
Chapter thirteen in the course was about the innate immune system. It started with a discussion of the physical mechanisms in the host used to prevent infection as well as chemical protective mechanisms. The innate immune system involves a nonspecific host response, including inflammation, which was explained in the chapter. The process of phagocytosis is crucial to the innate immune response; how this works was discussed in the chapter.
The topic of chapter fourteen was the adaptive immune system, which is far more specific against certain pathogens than the innate immune system. There are B cells that are responsible for making antibodies and T cells that participate in killing infected cells that have been marked with specific antibodies. Both the T cell line and the B cell line have memory cells that retain the memory of a past infection. Vaccines are given to provide immunity to individuals before they get an infection.
Chapter fifteen in the course talked about several different advance laboratory techniques used in the laboratory in the making of certain drugs and in the detection of diseases that cannot be identified with cultures. Antibodies are specific to a certain pathogen so there are techniques used to identify infectious diseases, which are generally viral in nature or involve fastidious pathogens for which antibodies have been made in the affected patient. Enzyme-linked immunosorbent assays or ELISA testing and fluorescent antibody testing are two of the techniques that were discussed in the chapter.
COURSE QUESTIONS AND ANSWERS
11. What type of bacterial species is rod-shaped?
e. Vibrio f. Bacillus g. Coccus h. Spirochete
Answer: b. The rod-shaped bacterial species is referred to as a Bacillus bacterium, of which the plural is called bacilli.
12. What type of organism is an amoeba?
a. Bacteria b. Algae c. Protozoa d. Fungi
Answer: c. Protozoa include amoeba, which are eukaryotic and move because they have pseudopodia or “false feet” that extend out from the cell body in a certain direction of movement in order to propel the organism from one place to another.
13. Which microorganism classically has a cell wall that is made from chitin?
a. Fungi b. Algae c. Archaea d. Bacteria
Answer: a. While each of these microorganisms has a cell wall, only fungi have a cell wall that is made from chitin specifically.
14. What is the cell wall of bacteria made from?
a. Cellulose b. Chitin c. Pseudopeptidoglycan d. Peptidoglycan
Answer: d. A characteristic that defines a bacterium is that it contains a peptidoglycan cell wall. The structure and component of the cell wall is often used as a defining feature to differentiate pathogens from one another.
15. Who was the most likely inventor of the first microscopes?
a. Zaccharias Janssen b. Galileo Galilei c. Robert Hooke d. Antonie van Leeuwenhoek
Answer: a. While each of these individuals contributed to the field of microscopy, the actual inventers who predated everyone were Hans and Zaccharias Janssen. They are credited with the findings, even though they never actually published their work.
16. If a compound microscope has an ocular lens that is 10 times magnification and an objective lens that has a four times magnification, what is the total magnification of this microscope?
a. 400 times b. 14 times c. 40 times d. 4000 times
Answer: c. The total magnification of the microscope is going to be the product of the magnifications of each lens, making the total 400 times magnification.
17. What feature on a light microscope will least likely affect the light reaching the specimen?
a. Illuminator b. Diaphragm c. Rheostat d. Coarse focusing knob
Answer: d. Each of these will have a role in controlling the level of light that reaches the specimen in different ways; however, the course focusing know primarily deals with putting the item in focus.
18. What is the maximum magnification you can get out of a typical laboratory compound light microscope?
a. 40 times b. 100 times c. 1000 times d. 10,000 times
Answer: c. The maximum that can be reached is about 1000 times. At this high magnitude, oil immersion of the specimen must take place in order to better focus the light and to maximize the resolution of the image.
19. Which microscopy technique will most detect specific pathogens in clinical microbiology?
a. Electron microscopy b. Light microscopy c. Fluorescence microscopy d. Dark field microscopy
Answer: c. Fluorescence microscopy makes use of tagged fluorescent antibodies that can specifically find certain pathogens that bind to the pathogen and fluoresce under the microscope.
20.Which type of microscopy uses low energy infrared light and fluorochromes to visualize objects under the microscope?
a. Confocal microscopy b. Darkfield microscopy c. Fluorescence microscopy d. Two-photon microscopy
Answer: d. With the two-photon microscope, fluorochromes are used and it uses such low energy light that two photons are necessary to excite the fluorochrome.
21. What is the magnification that can be gotten from an electron microscope?
a. 1000 times b. 10,000 times c. 100,000 times d. 2 million times
Answer: d. The magnification that can be gotten using an electron microscope is 2 million times that of the actual specimen.
22.What microscopy technique uses gold in order to highlight the specimen?
a. Scanning electron microscopy b. Two-photon microscopy c. Fluorescence microscopy d. Confocal microscopy
Answer: a. In scanning electron microscopy, the surface of the specimen is coated with gold in order to better highlight the specimen under the microscope.
23.What type of dye or stain is absorbed specifically by what you want to be able to see under the microscope?
a. Acidic dye b. Basic dye c. Negative stain d. Positive stain
Answer: d. The positive stain is any stain or dye that preferentially stains the item you are wanting to visualize under the microscope.
24.What is the first thing added to the four-step Gram stain procedure?
a. Iodine b. Crystal violet c. Safranin d. Ethanol
Answer: b. The first step is the addition of the crystal violet stain, which colorizes cells with a thick peptidoglycan layer first.
25. What color happens when safranin stains the cell wall of a bacterium?
a. Pink b. Purple c. Orange d. Green
Answer: a. The two main colors you will see with the Gram stain is purple and pink or red. When the thin peptidoglycan layers are decolorized and counterstained with safranin, they appear pink or red in color.
26.Which cellular organelles contain their own DNA?
a. Chloroplasts and mitochondria b. Mitochondria and Golgi bodies c. Lysosomes and Endoplasmic reticulum d. Peroxisomes and Golgi bodies
Answer: a. The two organelles, chloroplasts and mitochondria, each have their own DNA, which suggests that these structures originated from prokaryotic cells.
27. What is not a supportive fact indicating that chloroplasts and mitochondria descended from prokaryotic organisms?
a. These structures have their own DNA. b. These structures divide through binary fission. c. The ribosomes of these structures are similar to prokaryotic cells. d. These structures can exist and replicate outside of the cell.
Answer: d. Each of these statements is true and supportive of the endosymbiotic theory except that they do not divide or replicate outside of the eukaryotic cell.
28.The study of what disease caused Semmelweis to propose the germ theory of disease?
a. Wound infections b. Puerperal fever c. Gastroenteritis d. Plague
Answer: b. The first research indicating the probability of the germ theory of disease came out of a high incidence of puerperal fever among women who were examined by doctors rather than midwives.
29.What was the first epidemiological study about when it was performed in the middle 1800s?
a. Plague b. Common cold c. Cholera d. Influenza
Answer: c. The first epidemiological study was done by John Snow, who studied patterns of cholera in London as they related to certain water sources.
30.What best describes a chain of round bacteria in an arrangement?
a. Streptococcus b. Staphylococcus c. Streptobacillus d. Diplococcus
Answer: a. Streptococcus best describes round bacterial organisms arranged in a chain.
31. What will happen to a cell placed in a hypertonic medium?
a. It will burst or swell. b. It will shrink or crenate. c. It will neither shrink nor burst. d. What happens depends on the type of cell.
Answer: b. When placed in a hypertonic medium, the water in the cell will flow out of the cell, resulting in shrinkage or crenation of the cell.
32.What is the function of the nucleoid-associated proteins in prokaryotic cells?
a. They help in cell division. b. They assist in protein synthesis. c. They organize the genetic material. d. They assist in cellular respiration.
Answer: c. Nucleoid-associated proteins in prokaryotes will help to organize the nucleic acids or genetic material in the cell’s chromosome.
33. What is the most common substance found in a prokaryotic inclusion?
a. Iron oxide b. Volutin c. Gas d. Glycogen or starch
Answer: d. Most inclusions will store glycogen or starch for metabolism but the other choices can less commonly be seen in inclusions found in prokaryotic cells.
34.What is the main function of the glycocalyx in the immune response to bacteria?
a. It causes a decreased antibody response. b. It prevents immune cells from recognizing the cells as being foreign. c. It prevents clumping of the bacteria. d. It decreases the uptake of the bacterial cell by immune cells that might phagocytize them.
Answer: d. The main immune function of the glycocalyx is that it helps prevent bacterial uptake by phagocytic immune cells.
35. What prokaryotic cell structure is involved in the exchange of genetic material between two cells?
a. Fimbriae b. Flagella c. Pilus d. Cilia
Answer: c. There are certain types of pili called sex pili that confer the passage of genetic information between two cells of the same species.
36.Which cell structure is not seen in a prokaryotic cell at all?
a. Fimbriae b. Flagella c. Pilus d. Cilia
Answer: d. Prokaryotic cells have each of these appendages but they do not have cilia. Cilia are seen in animal eukaryotic cells.
37. What is the arrangement of flagella called that involves flagella that are all around the bacterium?
a. Peritrichous b. Amphitrichous c. Lophotrichous d. Monotrichous
Answer: a. Peritrichous flagella are those that surround the bacterial cell.
38.What structure in the eukaryotic cell is often referred to as the post office of the cell?
a. Smooth endoplasmic reticulum b. Golgi apparatus c. Mitochondria d. Lysosomes
Answer: b. The Golgi apparatus will sort and modify organic molecules in order to place them into vesicles, sometimes for transport out of the cell itself.
39.Which eukaryotic cell structure contains hydrogen peroxide for the breakdown of small molecules within the cell?
a. Peroxisome b. Lysosome c. Mitochondria d. Golgi apparatus
Answer: a. The peroxisome of the cell contains hydrogen peroxide, which is highly reactive and can break down multiple types of cellular molecules.
40.What two proteins in a cell are responsible for movement, such as is seen in muscle contraction?
a. Tubulin and keratin b. Keratin and Myosin c. Actin and myosin d. Actin and tubulin
Answer: c. The action of actin and myosin together help to create cell movement as can be seen in the contraction of muscle cells.
41. What is a protein found in certain intermediate filaments in the cell?
a. Actin b. Myosin c. Tubulin d. Desmin
Answer: d. Desmin is a protein found in intermediate filaments and makes up desmosomes, which bind two adjacent cells together.
42.Which process of the eukaryotic cell membrane is also referred to as cell drinking, which involves the intake of solutes and water in the cell?
a. Phagocytosis b. Exocytosis c. Pinocytosis d. Endocytosis
Answer: c. Pinocytosis is “cell drinking”, in which solutes and water are taken up by the cell from the outside.
43.What motor protein drives the movement of the flagella in eukaryotic organisms?
a. Kinesin b. Actin c. Tubulin d. Dynein
Answer: d. Dynein is the protein that makes up the motor abilities of the eukaryotic flagella, which themselves are flexible and made from microtubules.
44.What is a major difference between flagella and cilia?
a. Flagella are made from microtubules and cilia are not. b. Cilia can participate in eating nutrients and flagella cannot. c. Flagella are flexible while cilia are not. d. Cilia have basal bodies and flagella do not.
Answer: b. One of the major differences between cilia and flagella is that cilia can participate in sweeping nutrients into some organisms’ mouthparts, which is not the case with flagella that participate in movement only.
45. Transmission of a virus through getting bitten by an insect is called what?
a. Transmission through a biological vector b. Transmission through a mechanical vector c. Direct transmission d. Transmission through a fomite
Answer: a. In a biological vector transmission, one can get bit by an insect, which passes on the virus that was once internally located within the insect.
46.The part of the virus particle that is made from phospholipids is called what?
a. Capsid b. Capsomere c. Envelope d. Genome
Answer: c. Not all viruses have envelopes but some do. The viral envelope contains phospholipids and originate from somewhere in the host cell at the time the virion is released after being replicated.
47. Which type of virus has a sheath and tail pins extending from a polyhedral head?
a. Poxviruses b. Ebola c. Tobacco mosaic virus d. Bacteriophages
Answer: d. Bacteriophages have unique shapes that involve a headpiece and extensions that include a sheath and tail pins, which aid in the attachment of the viral particle.
48.What is not a way that virus particles are separately differentiated?
a. Positive or negative strandedness b. Degree of virulence c. Enveloped or naked d. Type of nucleic acid
Answer: b. Each of these is a way of differentiating different kinds of viruses, except they are not differentiated by their degree of virulence.
49.What stage of the viral life cycle happens just before biosynthesis?
a. Penetration b. Attachment c. Maturation d. Lysis
Answer: a. Penetration happens just before biosynthesis. In the viral life cycle, penetration involves injection of the genetic material, after which biosynthesis or the making of viral components occurs.
50.In which stage of the viral life cycle does genetic material get injected out of the bacteriophage?
a. Attachment b. Penetration c. Biosynthesis d. Maturation
Answer: b. During penetration, the viral genome is injected into the bacterial organism, while the actual viral particle remains on the outside of the bacterium.
51. What is the bacteriophage genome called when it incorporates into the host genome rather than kill the cell?
a. Lysogeny b. Phage conversion c. Prophage d. Lysogen
Answer: c. When the bacteriophage enters the host cell and becomes incorporated with the host genome, the phage is known as a prophage.
52. What is it called when the virus infecting a host increases the pathogenicity of the host bacterium?
a. Induction b. Lytic phase c. Maturation d. Lysogenic conversion
Answer: d. With lysogenic conversion, the characteristics of the host are changed by the presence of the prophage, generally causing an increase in the host cell’s pathogenicity. 53. Which type of transduction is linked to which type of viral life cycle?
a. General transduction and lysogenic life cycle b. General transduction and both lysogenic and lytic life cycle c. Specialized transduction and lytic life cycle d. Specialized transduction and lysogenic life cycle
Answer: d. The only true association listed involves specialized transduction, which is only associated with the lysogenic life cycle.
54. What is a provirus?
a. A newly released viral particle b. A piece of viral DNA incorporated into the DNA of a host cell c. A piece of viral nucleic acid that has just been taken up by the host cell d. The virus particle that has been excised out of the host genome
Answer: b. A provirus is what the viral genome is called when it gets incorporated into the DNA of a host cell.
55. Where in the human body does the latent virus that causes chickenpox remain dormant?
a. Brain b. Respiratory tract c. Nerve cell bodies d. Skin cells
Answer: c. The chickenpox virus will lie dormant in the nerve cell bodies near the spinal cord before they come out to cause a herpes zoster infection along the route of the nerve in the body.
56. What type of viral genome gets directly translated into proteins?
a. Positive single stranded RNA b. Double-stranded DNA c. Negative single-stranded RNA d. Negative single-stranded DNA
Answer: a. Only positive single-stranded RNA viral genomes get directly translated into proteins. This is the case with most plant viruses.
57. What is mixed together in a hemagglutinin inhibition assay?
a. Red blood cells and viruses in serum b. Red blood cells, viruses in serum, and virus-specific antibodies c. White blood cells and viruses d. Patient’s whole blood and antibodies against the virus
Answer: b. In a hemagglutinin inhibition assay, red blood cells and the patient’s serum are mixed with virus-specific antibodies. The antibodies bind the virus and inhibit the hemagglutination of the red blood cells.
58.What does a viroid consist of?
a. Circular RNA segments only b. DNA segments and a simple protein coat c. RNA segments and a lipid coat d. Protein segments only
Answer: a. A viroid is a circular RNA segment only that does not have a protein coat. The RNA segment can hijack the host cell’s replication enzymes.
59. What is the primary difference between a virusoid and a viroid?
a. A viroid is an RNA particle and a virusoid is a DNA particle. b. A viroid is more complex than a virusoid. c. A virusoid requires a helper virus to cause the infection. d. A viroid will kill a cell, while a virusoid is a latent infection.
Answer: c. A virusoid requires a helper virus in order to cause the infection while a viroid can cause an infection without having a helper virus infection.
60.Which type of symbiosis involves one population benefiting from the relationship and the other population being harmed?
a. Mutualism b. Commensalism c. Amensalism d. Parasitism
Answer: d. With parasitism, one population in the relationship receives a benefit, while others are harmed by the relationship.
61. Which type symbiosis involves both populations in the relationship benefitting from the relationship between the two?
a. Mutualism b. Neutralism c. Commensalism d. Amensalism
Answer: a. In mutualism, both populations in the relationship will receive benefit from being in the relationship.
62.Which type of bacterium is not considered atypical?
a. Rickettsia b. Mycoplasma c. Haemophilus d. Chlamydia
Answer: c. Haemophilus is a gram-negative organism, while the rest of them are atypical because they either do not stain with gram staining procedures or are too small to see.
63.Which type of proteobacteria is the most diverse?
a. Alpha-proteobacteria b. Beta-proteobacteria c. Gamma-proteobacteria d. Delta-proteobacteria
Answer: c. There are many different organisms contained within the category of gamma-proteobacteria. These include Vibrio cholerae, Pseudomonas, Legionella, and Pasteurella.
64.Which type of proteobacteria can live on very few nutrients?
a. Alpha-proteobacteria b. Beta-proteobacteria c. Gamma-proteobacteria d. Delta-proteobacteria
Answer: a. Those who are alpha-proteobacteria can live on very few nutrients. They are often found in deep soil or deep oceanic sedimentary habitats.
65. Which type of proteobacteria are very fastidious and difficult to grow because they need a great many nutrients to survive?
a. Alpha-proteobacteria b. Beta-proteobacteria c. Gamma-proteobacteria d. Delta-proteobacteria
Answer: b. The beta-proteobacteria live in different environments and cause human diseases but they require a great many nutrients and are difficult to grow outside of the human host.
66.What is not a characteristic of spirochetes?
a. They can be grown in agar or tissue cultures. b. They are highly motile. c. They can cause Lyme disease and syphilis. d. They cannot easily be seen using regular light microscopy.
Answer: a. Each of these is a characteristic of spirochetes, except that they are nearly impossible to grow in any type of culture.
67. Which bacterial genus is not a part of the CFB phylum of gram-negative bacteria?
a. Fusobacterium b. Bacillus c. Bacteroides d. Cytophaga
Answer: b. Each of these organisms belongs to the CFB phylum and are similar to one another because they share certain genetic characteristics.
68.What genus of gram-negative bacteria comprise the majority of the normal human intestinal biome?
a. Bacillus b. Enterobacter c. Bacteroides d. Fusobacterium
Answer: c. The majority of the human intestinal biome consists of species of the genus Bacteroides, which are largely mutualistic to humans because they prevent the overgrowth of pathogenic bacteria.
69.What is made mostly in those phototrophic bacteria that do not make oxygen?
a. Nitrogen b. Sulfur c. Carbon dioxide d. They all make oxygen
Answer: b. Those phototrophs that do not make oxygen are called anoxygenic species. They generally make elemental sulfur as their end product.
70.What species of bacterial organism is considered an acid-fast bacillus?
a. Corynebacterium b. Listeria c. Mycobacterium d. Actinomyces
Answer: c. Mycobacterium species are particularly well known to be acid-fast in nature because their coat contains mycolic acid that must be specially stained in order to be visualized.
71. What is not a similar feature of organisms like Mycobacteria, Corynebacterium, Bifidobacterium, and Propionibacterium?
a. They are all motile bacteria. b. They are all Actinobacteria. c. They are all high-GC bacteria. d. They fall under the category of gram-positive bacteria.
Answer: a. Each of these is a feature of these organisms except that they are not all motile. In fact, very few of them are motile.
72. Which organism type is considered to be evolutionarily the oldest and most ancient?
a. Eukarya b. Bacteria c. Deeply branching bacteria d. Archaea
Answer: c. The deeply branching bacteria are called what they’re called because they represent the furthest branches and the oldest ancestors of common organisms found today.
73. What is sexual reproduction called in protozoal life cycles?
a. Syngamy b. Encapsulation c. Encystment d. Sporulation
Answer: a. Syngamy is the reproductive life cycle aspect of protozoans. It involves sexual reproduction with male and female merozoites.
74. Which is not a form of asexual reproduction in protozoans?
a. Schizogony b. Binary fission c. Conjugation d. Budding
Answer: c. Each of these is a form of asexual reproduction in protozoans except for syngamy and conjugation, which are considered sexual reproductive methods of passing on progeny.
75. What is the main purpose of the protostome in protozoal organisms?
a. Motility b. Feeding c. Waste production d. Immunity
Answer: b. The protostome is a specialized feeding structure that engages in the phagocytosis of nutrients by the protozoan.
76. What organelle does the kinetoplastid replace inside some protozoal organisms?
a. Microtubules b. Nucleolus c. Mitochondrion d. Golgi apparatus
Answer: c. The kinetoplastid is a modified mitochondrion seen in some types of protozoans instead of true mitochondria.
77. Which eukaryotic microbe is not of the Excavata supergroup?
a. Leishmania b. Entamoeba c. Trichomonas d. Giardia
Answer: b. Entamoeba does not belong to the Excavata supergroup but instead belongs to the Amoebozoa supergroup. The others belong to the Excavata supergroup.
78. Which is not an animal-based parasitic infection?
a. Candidiasis b. Schistosomiasis c. Trichinosis d. Cestode infections
Answer: a. Each of these is an animal-based parasitic infection with the exception of candidiasis, which is a fungal infection instead.
79. In the paramecium, what is the micronucleus used for?
a. Metabolism b. Conjugation c. Formation of fruiting bodies d. As a backup nucleus
Answer: b. The micronucleus is used for conjugation. It contains a diploid set of chromosomes that undergo meiosis and get exchanged between two adjacent paramecium cells.
80.Which Excavata organism is not pathogenic?
a. Euglena b. Giardia c. Trypanosoma d. Trichomonas
Answer: a. Euglena is a subgroup of Excavata that has been well studied. It is photosynthetic and is generally not considered a pathogenic organism.
81. What type of hyphae are characterized by having cell walls between the different cells of the hypha?
a. Coenocytic b. Thallus c. Pseudohyphae d. Septate
Answer: d. Septate hyphae are those that have cell walls between the different organism that together form the hyphae of the fungal organism.
82.Which nematode infection is the most common of these types of infections in the US?
a. Pinworms b. Hookworms c. Ascaris d. Toxocariasis
Answer: a. Pinworm infestation are the most common nematode infection in the United States, primarily affecting the GI tracts of young children.
83.Which part of the body besides the GI tract is affected by the larval forms of the Trichinella nematode?
a. Skin b. Brain c. Muscle d. Kidneys
Answer: c. Trichinellosis comes from eating undercooked meat. It can encyst the larval forms within muscle tissue, leading to muscle aches and related muscle symptoms.
84.Which helminth infection is found in freshwater snails and burrows through the skin, leading to disseminated disease?
a. Liver flukes b. Intestinal flukes c. Lung flukes d. Schistosomiasis
Answer: d. Schistosomiasis is a common infection worldwide that is found in freshwater snails. It can lead to a disseminated infection and death if not treated.
85.What is the hard shell of diatoms made of?
a. Chitin b. Cellulose c. Peptidoglycan d. Silica
Answer: d. Diatoms have a hard shell from silica that contributes to diatomaceous earth.
86.What two organisms combine to make a lichen?
a. Green algae and cyanobacteria b. Green plants and diatoms c. Diatoms and cyanobacteria d. Protozoans and brown algae
Answer: a. Lichens are a combination of green algae and cyanobacteria that work cooperatively to do things like break down rocks, stabilize soil, and fix nitrogen.
87. What element is among the micronutrients or trace elements inside living things?
a. Potassium b. Phosphorus c. Nitrogen d. Hydrogen
Answer: a. Each of these represents a macronutrient except for potassium which, along with other metallic substances, are primarily trace elements or micronutrients.
88.What type of chemical bond is most commonly seen with organic molecules?
a. Ionic bond b. Hydrogen bond c. Metallic bond d. Covalent bond
Answer: d. A covalent bond is one in which electrons are roughly shared with one another; these bonds are relatively difficult to break compared to the other types of bonds.
89.Organic molecules with the same number of atoms that are arranged differently in the molecule are referred to as what specifically?
a. Structural isomers b. D-enantiomers c. Chiral d. L-enantiomers
Answer: a. Structural isomers have the same basic atoms in them but have different arrangements of the atoms in the molecule.
90.Which biomolecule type is involved in the storage or transfer of genetic information?
a. Lipids b. Proteins c. Carbohydrates d. Nucleic acids
Answer: d. Nucleic acids are unique in that they come together to store or participate in the transfer of the cell’s genetic information. 91. What type of fatty acid has no double bonds in it between carbon atoms?
a. Saturated fatty acids b. Trans fatty acids c. Monounsaturated fatty acids d. Polyunsaturated fatty acids
Answer: a. Saturated fatty acids are saturated with hydrogen atoms and have no double bonds between the different carbon atoms.
92.Which type of lipid makes up the most of the cell membrane of a typical cell?
a. Fatty acid b. Triglyceride c. Phospholipid d. Cholesterol
Answer: c. The majority of the cell membrane is made from phospholipids, which have a polar end and a nonpolar end.
93.What type of lipid makes waxes, fragrances, and pigments?
a. Phospholipids b. Sterols c. Isoprenoids d. Ergosterols
Answer: c. Isoprenoids will make many different things, including pharmaceuticals, waxes, fragrances, and pigments.
94.What molecule in the cell membrane of fungi differentiate it from animal and bacterial cell membranes?
a. Ergosterols b. Cholesterol c. Hopene d. Hopanoids
Answer: a. Ergosterol is the main component that is not phospholipids in the fungal cell membrane, which differentiates these compounds from other organisms.
95. What is the smallest component of a protein molecule?
a. Protein b. Amino acids c. Oligopeptides d. Polypeptides
Answer: b. Amino acids are the smallest component of these molecules, which makes them the building blocks of the molecules.
96.What aspect of protein structure involves the exact arrangement of the amino acids in the chain?
a. Primary structure b. Secondary structure c. Tertiary structure d. Quaternary structure
Answer: a. the primary structure of a protein is determined specifically by the arrangement of the amino acids in the protein structure.
97. What aspect of a protein gives it a specific shape because of interactions between the side chains, such as the formation of disulfide bonds?
a. Primary structure b. Secondary structure c. Tertiary structure d. Quaternary structure
Answer: c. The tertiary structure of a protein molecule involves an interaction between the side chains. It includes things like the formation of a disulfide bond, hydrogen bonding, and ionic bonding.
98.Which element is not routinely found in a carbohydrate molecule?
a. Carbon b. Hydrogen c. Oxygen d. Nitrogen
Answer: d. The elements of carbon, hydrogen, and oxygen are necessary in order to make a carbohydrate. Only in rare circumstances would nitrogen be attached to a carbohydrate molecule.
99.Which is not one of the major polysaccharides found in nature?
a. Maltose b. Glycogen c. Starch d. Cellulose
Answer: a. Each of these is a polysaccharide found in nature but maltose is an uncommon disaccharide and is not considered a polysaccharide.
100. Organisms that get their carbon source from carbon dioxide are called what?
a. Phototrophs b. Heterotrophs c. Autotrophs d. Lithotrophs
Answer: c. Autotrophs have the ability to get carbon for their organic molecules from carbon dioxide. This is opposed to heterotrophs, which get their energy from organic molecules.
101. What kind of organism includes humans and other animals when it comes to energy and carbon sources?
a. Chemoautotrophs b. Chemoheterotrophs c. Photoautotrophs d. Photoheterotrophs
Answer: b. All animals as well as fungi and other species are chemoheterotrophs. They get their energy from organic molecules and get their carbon sources also from organic molecules.
102. Which kind of organism includes all plants when it comes to energy and carbon sources?
a. Chemoautotrophs b. Chemoheterotrophs c. Photoautotrophs d. Photoheterotrophs
Answer: c. Plants are classified as photoautotrophs because they get their energy source from the sun and they get their carbon sources from carbon dioxide, which is an inorganic molecule.
103. What is an enzyme called that is inactive because it does not have its helper enzymes associated with it?
a. Holoenzyme b. Apoenzyme c. Cofactor d. Coenzyme
Answer: b. An enzyme that is inactive because it does not have its cofactors or coenzymes associated with it. When this happens, it is referred to as a holoenzyme.
104. What is the beginning and ending molecule in glycolysis?
a. Glucose is the starting substrate and pyruvate is the end product. b. Glucose is the starting substrate and carbon dioxide is the end product. c. Amino acids are the starting product and glucose is the end product. d. Lipids are the starting product and carbon dioxide is the end product.
Answer: a. In glycolysis, there is glucose as the starting product, and pyruvate is the end product of multiple reactions.
105. In the glycolysis pathway, how many net ATP molecules are made per glucose molecule?
a. One b. Two c. Three d. Four
Answer: b. There are two ATP molecules used up in the investment phase, while four ATP molecules are made later, making a total of two ATP molecules made net in the reaction.
106. What is not true of the Krebs cycle?
a. It consumes ATP energy. b. It makes two molecules of CO2. c. It is a closed loop. d. It involves the participation of coenzyme A.
Answer: a. Each of these is true of the Krebs cycle, except that it makes a molecule of ATP but does not consume ATP energy.
107. What is least likely to be an end product of heterolactic fermentation?
a. CO2 b. Oxygen c. Acetic acid d. Ethanol
Answer: b. In heterolactic fermentation, things like CO2, acetic acid, and ethanol can be made as part of the fermentation process.
108. What is the end product of muscle fermentation in the absence of oxygen?
a. Ethanol b. CO2 c. Lactic acid d. Acetic acid
Answer: c. Muscle cells are homolactic, meaning they only make lactic acid as an end product of fermentation.
109. What is not a reason why a cell will not be able to undergo oxidative phosphorylation?
a. There is insufficient oxygen in the environment. b. There has not been enough pyruvate made. c. The genes to make electron transport chain proteins are missing. d. The genes to protect the cell from oxygen free radicals are missing.
Answer: b. Each of these is a reason why oxidative phosphorylation cannot happen, except that there will not be enough pyruvate, which is uninvolved in the electron transport chain.
110. Those organisms that engage in anaerobic respiration will make what after the electron chain is complete?
a. Sulfur b. Sulfite c. Nitrate d. Nitrogen gas
Answer: d. Those organisms that participate in anaerobic respiration are involved in denitrification so they take nitrate or nitrite to make nitrogen gas as an end product.
111. What does the hydrogen ion gradient made through chemiosmosis get used to do?
a. Help the electron transport chain make CO2 and water. b. Help drive the sodium-potassium ATPase pump. c. Help drive ATP synthase to make ATP. d. Help in acid-base balance inside the cell.
Answer: c. The hydrogen ion gradient can drive several kinds of reactions but is most important in driving ATP synthase to make ATP energy.
112. Which is not likely to be a temporary storage molecule made in the lightindependent phase of photosynthesis?
a. ATP b. NADH c. NADPH d. FADH2
Answer: d. Each of these is made as a temporary storage molecule in the light-independent phase of photosynthesis; however, FADH2 is not made.
113. What process most directly gets nitrogen gas back into the atmosphere?
a. Nitrogen fixation b. Ammonification c. Anaerobic respiration d. Aerobic respiration
Answer: c. Anaerobic respiration uses nitrite or nitrate and make nitrogen gas that get back into the atmosphere. Certain bacteria will participate in this process.
114. The phosphodiester bond in DNA links which carbon atoms on the deoxyribose sugar together?
a. Five-prime to five-prime b. Five-prime to three-prime c. Four-prime to two-prime d. Three-prime to one-prime
Answer: b. The phosphodiester linkage in DNA links a five-prime carbon atom on one molecule or deoxyribose to the three-prime carbon atom on an adjacent sugar molecule.
115. What is said with regard to Chargaff’s rule in the structure of DNA? a. That DNA is made from nucleotides b. That adenine and thymine go together and guanine and cytosine go together c. That the genetic material inside the cell comes from DNA d. That DNA consists of a double helical shape
Answer: b. Chargaff’s rule was related to the fact that adenine binds to thymine and cytosine binds to guanine.
116. Which nitrogenous base is not found in DNA?
a. Adenine b. Guanine c. Cytosine d. Uracil
Answer: d. While each of these is a nitrogenous base, only adenine, guanine, cytosine, and thymine are found in DNA. Uracil is a nitrogenous base that is instead found in RNA.
117. What is not a difference between DNA and RNA?
a. RNA does not have a phosphodiester bond. b. RNA segments tend to be shorter. c. RNA contains ribose and DNA contains deoxyribose. d. RNA tends to be single stranded.
Answer: a. These are the major differences between RNA and DNA except that RNA is the same as DNA when it comes to having phosphodiester bonds.
118. What nitrogenous base in DNA will be replaced by uracil?
a. Adenine b. Guanine c. Thymine d. Cytosine
Answer: c. Thymine is not present in RNA but is replaced completely by uracil instead. In such cases, adenine pairs with uracil.
119. Which base pair in DNA is hydrogen bonded to Adenine?
a. Cytosine b. Thymine c. Uracil d. Guanine
Answer: b. Adenine will form base pairs with thymine in the DNA molecule.
120. Where does ribosomal RNA processing happen in eukaryotes?
a. Nucleolus b. Nucleus c. Cytoplasm d. Ribosomes
Answer: a. Processing of ribosomal RNA in eukaryotes happens in the nucleolus but in prokaryotes, it happens in the cytoplasm.
121. Which RNA type has enzymatic activity, helping to make the peptide bond?
a. Messenger RNA b. Transfer RNA c. Ribosomal RNA d. Small nuclear RNA
Answer: c. Ribosomal RNA is the only type of RNA known to have enzymatic activity because it helps to form the peptide bond in the ribosome.
122. What is it called when DNA makes a copy of itself?
a. Translation b. Replication c. Modification d. Transcription
Answer: b. Replication is the synthesis of DNA from another DNA strand.
123. What is the name given to a region of DNA that encodes for a single protein?
a. Chromosome b. Genome c. Gene d. Constitutive gene
Answer: c. A segment of a genome that is a region of DNA that can encode for a single protein is called a gene. There are hundreds or thousands of genes per genome, depending on the organism.
124. What is the name of a gene that is always turned on?
a. Unexpressed gene b. Genotype c. Facultative gene d. Constitutive gene
Answer: d. A constitutive gene or housekeeping gene is a gene that is so important that it is always turned on. On the other hand, a facultative gene is one that is only turned on or expressed when needed.
125. What is the protein or enzyme that causes supercoiling of the DNA in a genome?
a. DNA polymerase b. Topoisomerase c. Histone d. Chromatin
Answer: b. Topoisomerase is the enzyme that supercoils the DNA so that it can fit better inside a given cell. Otherwise, the DNA would be too long to fit inside each cell.
126. Which type of organism tends to have the largest genomes?
a. Bacteria b. Fungi c. Viruses d. Plants
Answer: d. Plants often have very large genomes and are often polyploid, having many copies of the same chromosomes.
127. What is the main function of DNA polymerase I and DNA polymerase II in
DNA replication?
a. DNA synthesis b. DNA strand separation c. DNA repair d. DNA uncoiling
Answer: c. These types of DNA polymerase are most involved in the repair of DNA segments rather than actual DNA synthesis.
128. What enzyme in DNA replication is responsible for is responsible for separating the DNA strands in order to make the replication fork?
a. Topoisomerase II b. DNA gyrase c. DNA polymerase d. Helicase
Answer: d. Helicase is the enzyme in the cell that is involved in the separation of the DNA strands. This helps to create the replication fork.
129. What is not true of the lagging strand in DNA replication?
a. It involves a single primer b. It involves the making of Okazaki fragments c. Synthesis is discontinuous d. There needs to be multiple primers
Answer: a. The lagging strand involves multiple primers and the making of Okazaki fragments. The synthesis is discontinuous.
130. Which enzyme in DNA synthesis will connect two different segments of the DNA strand?
a. Helicase b. DNA polymerase I c. DNA ligase d. DNA polymerase III
Answer: c. DNA ligase is responsible for creating a phosphodiester bond between two adjacent sections of DNA.
131. The shortening of what part of the chromosome might be responsible for cellular aging?
a. Telomeres b. Origin of replication c. RNA primers d. Structural genes
Answer: a. It is believed that the shortening of the telomeres is responsible for the aging of the cells. Telomeres shorten with each cell division.
132. What is involved with plasmid replication that isn’t present in regular bacterial replication?
a. Synthesis happens at the three-prime to five-prime end. b. DNA polymerase is not involved. c. The DNA strand gets nicked instead of making a replication bubble. d. The plasmid does not replicate.
Answer: c. In the replication of plasmid DNA, the strand gets nicked and comes off, causing the nicked strand to circularize and both strands to get replicated with DNA polymerase.
133. RNA polymerase adds nucleotides in which direction?
a. The three-prime to five-prime direction b. The five-prime to three-prime direction c. In both directions d. They get added at the same time and then spliced together
Answer: b. The RNA polymerase always makes RNA in the five-prime to three-prime direction.
134. What does it mean that a segment of RNA is polycistronic?
a. It means that there are segments that do not code for a protein. b. It means that it is transcribed without a promotor region. c. It means that it is turned on by an operator region. d. It means that it codes for several proteins at the same time.
Answer: d. The polycistronic RNA segment will code simultaneously for multiple proteins at the same time. This is common in prokaryotes but not in archaea and eukaryotes.
135. What does not happen to pre-messenger RNA in order to prepare it for export out of the nucleus?
a. The different polypeptide coding regions get separated. b. The Poly-A tail gets added to the messenger RNA. c. The five-prime cap gets added to the messenger RNA. d. The introns get spliced out of the pre-messenger RNA.
Answer: a. Each of these things happens as part of the processing of RNA before it is exported out of the nucleus but, in eukaryotes, there is generally one messenger RNA per protein so there is no need to separate polypeptide coding regions.
136. How many base pairs constitute a codon?
a. Two b. Three c. Four d. Six
Answer: b. One codon is a triplet of base pairs, each of which translates into a different amino acid.
137. How many amino acids are there in nature that make proteins?
a. 10 b. 20
c. 32 d. 64
Answer: b. There are 20 different amino acids in nature that together make the different proteins.
138. Which amino acid is the first amino acid added to the peptide when translation takes place in the eukaryote?
a. Glutamine b. Histidine c. Alanine d. Methionine
Answer: d. Methionine is always the first amino acid in eukaryotes to be added to make a protein in translation. A modified form of methionine is the initial amino acid in prokaryotes.
139. Which type of mutation in a codon only affects the cell in certain environmental circumstances?
a. Nonsense mutation b. Conditional mutation c. Missense mutation d. Silent mutation
Answer: b. A conditional mutation is some type of missense mutation that only affects the cell under certain environmental circumstances.
140. What type of mutagen most likely leads to dimer formation between adjacent pyrimidines?
a. Intercalating agents b. Nucleoside analogs c. Nonionizing radiation d. Ionizing radiation
Answer: c. Nonionizing radiation, which is what ultraviolet rays are, will lead to dimer formation between adjacent pyrimidines, which can lead to mutations.
141. What does the activator bind to in order to increase transcription of an operon in a prokaryote?
a. RNA polymerase b. Promotor site c. Repressor d. Operator
Answer: b. The activator will bind to the promotor site, increasing the ability of the RNA polymerase to bind to the DNA molecule and cause transcription.
142. Which is a small regulatory molecule in prokaryotes that can interact with other molecules in order to activate or repress transcription?
a. Inducer b. Promotor c. Operator d. Repressor
Answer: a. An inducer is a small molecule that interacts with either an activator or repressor in order to increase or decrease transcription of a prokaryotic operon.
143. Under what physiological conditions does the lac operon get transcribed to the greatest degree?
a. Glucose is low and lactose is low b. Glucose is low and lactose is high c. Glucose is high and lactose is high d. Glucose is high and lactose is low
Answer: b. Under conditions of low glucose and high lactose, the lac operon transcription is turned on the most. This is because the cell prefers glucose as a fuel source, so it needs to be low before lactose is used as an energy source.
144. What gene regulation type is available to eukaryotes but not to prokaryotes?
a. Inducers b. Activators c. Repressors d. Enhancers
Answer: d. Enhancers involve the presence of a specific DNA sequence a distance away from promotor sites that get close to the promotor site through looping of DNA. It will be seen in eukaryotes but not in prokaryotes.
145. Which method of gene transfer does not occur between members of the same generation in prokaryotes?
a. Vertical transmission b. Transduction c. Conjugation d. Transformation
Answer: a. With vertical transmission, the DNA is passed from one cell to the daughter cells in the next generation.
146. Which method of gene transfer in prokaryotes involves the transfer of
DNA through pili between the cells?
a. Vertical transmission b. Transduction c. Conjugation d. Transformation
Answer: c. Conjugation in prokaryotes involves the direct transfer of DNA through pili that connect two cells together.
147. Which genetic change occurs in both prokaryotes and eukaryotes?
a. Transduction b. Transposition c. Conjugation d. Transformation
Answer: b. Each of these occurs in just prokaryotic cells; however, transposition or the transfer of transposons from one DNA area to another, occurs in both eukaryotes and prokaryotes.
148. In which phase of the cell growth curve in a fixed culture is the maximum culture density reached?
a. Log phase b. Stationary phase c. Lag phase d. Decline phase
Answer: b. In the stationary phase, the log phase has already occurred and the maximum culture density is reached.
149. What is not true of using the Petroff-Hausser chamber for detecting bacterial cell concentrations?
a. It does not work for very dilute solutions. b. It cannot easily tell the difference between dead and live cells. c. It involves a microscopic analysis of cell counts. d. Fluorescence staining cannot be used.
Answer: d. Each of these is a true statement with regard to PetroffHausser chambers except that fluorescence staining will be able to tell the difference between dead and live cells.
150. What is the main advantage of the plating method for detecting the number of bacteria in a colony?
a. It only detects living cells. b. It can count organisms that normally form chains or clusters. c. It can detect very low or very high concentrations. d. It is the fastest method of detection of cells.
Answer: a. The biggest advantage is that it can detect only living cells that can thrive on a culture plate. It is not able to accurately count cells that grow in chains or clusters and is not a fast method of detection because the colonies must be allowed to grow on the plate.
151. In a biofilm, what is quorum sensing?
a. It is the formation of an extracellular matrix. b. It is the formation of waste, nutrient, and water channels. c. It is the ability of the organisms to share nutrients. d. It is the ability of the biofilm organisms to sense their own density.
Answer: d. Quorum sensing can be important to virulence of the organisms in the biofilm. It is the ability of the organisms to sense their own density and to increase virulence when the density is high enough.
152. Which organism in a thioglycolate tube will grow throughout the tube’s length?
a. Strict aerobes b. Facultative anaerobes c. Aerotolerant anaerobes d. Strict anaerobes
Answer: c. Aerotolerant anaerobes rely on anaerobic metabolism but are completely tolerant of the presence of oxygen.
153. Which organisms in a thioglycolate culture tube will only grow at the bottom of the tube?
a. Strict aerobes b. Facultative anaerobes c. Aerotolerant anaerobes d. Strict anaerobes
Answer: d. Strict anaerobes do not like oxygen so they preferentially grow where the oxygen concentration is the lowest, which is at the bottom of the tube.
154. Capnophiles grow best when what is present in the environment?
a. Sulfur b. Oxygen c. Carbon dioxide d. Nitrogen
Answer: c. Capnophiles grow best in low oxygen and high carbon dioxide environments.
155. What do acidophile bacteria do to tolerate the low pH environments they live in?
a. They pump hydrogen ions outside the cell membrane. b. They have specialized enzymes that do not denature in an acidic environment. c. They create a mucus coat that repels hydrogen ions. d. They have an especially thick peptidoglycan layer in their cell wall.
Answer: a. These organisms actively pump hydrogen ions outside of their cell membrane in order to tolerate an acidic environment.
156. Which organisms prefer temperatures below freezing temperatures?
a. Alkaliphiles b. Psychrotrophs c. Acidophiles d. Psychrophiles
Answer: d. Psychrophiles are organisms that specifically like to live in temperatures that are below freezing, such as would be seen in Antarctica.
157. Which biological safety level involves organisms that are generally lethal and have no cure, such as Ebola?
a. BSL-1 b. BSL-2 c. BSL-3 d. BSL-4
Answer: d. BSL-4 organisms are the most dangerous and cause lethal infections for which there is no cure. The highest level of protection is required for these organisms.
158. What is the highest degree applied to a technique that will definitely rid an item from microorganisms and endospores?
a. Sterilization b. Disinfecting c. Antisepsis d. Degerming
Answer: a. Sterilization will get rid of all organisms and endospores from something, providing the greatest degree of protection from bacterial contamination.
159. What will least likely kill an organism with a chemical agent?
a. High concentrations of organisms b. Short contact times with the agent c. The presence of endospores d. The agent being bactericidal
Answer: b. Short contact times will least likely kill an organism with a chemical agent, regardless of the organism or the actual agent involved.
160. Which substance for getting rid of bacteria is not an antiseptic?
a. Surfactant b. Heavy metals c. Halogens d. Phenolics
Answer: a. Surfactants are not antiseptics but work to degerm an area of bacteria. These include both detergents and soaps.
161. What chemical is used to make a supercritical fluid in order to kill many pathogens?
a. Oxygen b. Carbon dioxide c. Nitrogen d. Hydrogen peroxide
Answer: b. Carbon dioxide is used as a supercritical fluid in order to sterilize things under high pressures and sometimes high temperatures.
162. What is least likely to affect the dosage of an antimicrobial drug given to a patient?
a. The patient’s mass b. The presence of liver disease c. The presence of kidney disease d. The presence of a drug allergy
Answer: d. Each of these will cause a problem with the dosage given to the patient except for the presence of a drug allergy, which is not dosedependent.
163. Which type of infection is best treated with an oral drug, even if the drug is poorly absorbed?
a. Sepsis b. Gastrointestinal infection c. Skin infection d. Liver infection
Answer: b. GI infections often can be treated with oral antibiotics, including those that are not easily absorbed by the gastrointestinal tract. These drugs can decontaminate the bowels.
164. Which drug classification is not a beta-lactam antibiotic?
a. Polymyxin B b. Penicillins c. Carbapenems d. Cephalosporins
Answer: a. Each of these is a beta-lactam drug belonging to a class of drugs that started with the discovery of penicillin. Polymyxin B is not one of these drugs.
165. Which drug affects the synthesis of the cell wall by preventing peptidoglycan subunits from getting from the inside to the outside of the cell membrane?
a. Vancomycin b. Bacitracin c. Penicillin d. Aztreonam
Answer: b. Bacitracin is unique in that it prevents peptidoglycan subunits from exiting the cell in order to prevent cell wall synthesis.
166. What is least likely to be a part of the body damaged by the use of aminoglycosides?
a. Nerves b. Ears c. Kidneys d. Liver
Answer: d. Aminoglycosides are mainly toxic to the nerves, ears, and kidneys. They are not generally considered toxic to the liver.
167. What is least likely to be affected by using the tetracycline class of antibiotics?
a. Skin b. Liver c. Ears d. Teeth
Answer: c. Tetracyclines can cause sunburn, liver damage, and teeth discoloration. They are not ototoxic and do not affect hearing.
168. Which part of the bacterium is affected with drugs like daptomycin and polymyxin B?
a. Cell wall b. Cell membrane c. DNA synthesis d. Protein synthesis
Answer: b. These drugs inhibit the synthesis of the cell membrane, sometimes affecting the outer membrane of gram-negative drugs.
169. What part of the cell is affected by fluoroquinolone drugs?
a. Cell membrane b. Cell metabolism c. DNA synthesis d. Protein synthesis
Answer: c. These drugs inhibit DNA gyrase so they prevent replication of DNA in the cells of bacteria—both gram-negative and gram-positive.
170. What part of the fungal organism is most effectively treated with imidazole drugs?
a. Cell membrane synthesis b. Cell wall synthesis c. Protein synthesis d. DNA replication
Answer: a. Because the fungal cell membrane contains ergosterol not seen in humans, these drugs selectively target ergosterol synthesis, affecting the fungal cell membrane.
171. What is the most common activity of antiviral drugs?
a. They inhibit protein synthesis b. They block virus attachment c. They are nucleoside analogs d. The cause breakage of DNA linkages
Answer: c. The majority of antiviral drugs act as nucleoside analogs that mimic certain nucleosides, affecting nucleic acid synthesis.
172. What virus is affected with drugs like Tamiflu and Relenza?
a. Influenza b. Hepatitis C c. Herpesviruses d. HIV
Answer: a. These drugs will specifically treat influenza, which will be prevented from releasing outside of the host cell it infects.
173. What least likely contributes to antimicrobial drug resistance?
a. Patient noncompliance b. Overprescribing antimicrobials c. Using the wrong antimicrobial d. Giving doses that are too high
Answer: d. Each of these will contribute to antimicrobial drug resistance except for giving doses that are too high. In fact, giving doses that are too low will more likely contribute to drug resistance.
174. What is true of the MBC and the MIC of an antimicrobial drug?
a. It will not depend on the organism being studied. b. The MBC and the MIC should be roughly the same. c. The MIC will be greater than the MBC. d. The MBC will be greater than the MIC.
Answer: d. The MBC is the concentration of drug that will kill 99.9 percent of the organism, while the MIC is the minimum inhibitory concentration. The MBC will be greater than the MIC.
175. What least likely affects the length of the incubation period in an infectious disease?
a. The organism’s virulence b. The size of the inoculum c. Host immunity level d. Each of these affects the incubation period
Answer: d. There are many factors involved in disease incubation periods, including the route of entry and the type of organism involved.
176. Transmission and contagiousness of a pathogen during which phase of the infectious disease confers the greatest advantage to the pathogen?
a. Incubation b. Prodromal c. Illness d. Convalescence
Answer: b. The ability of a pathogen to transmit during the prodromal period confers an advantage to the pathogen because it means that the organism can transmit before the person can be quarantined in order to prevent further disease spread.
177. During which phase of an infectious disease are the symptoms nonspecific but noticeable?
a. Incubation b. Illness c. Convalescence d. Prodromal
Answer: d. In the prodromal phase, there will be nonspecific symptoms, such as fever, malaise, or inflammation but the true syndromal symptoms are not seen yet.
178. Which disease is more likely to be a chronic disease rather than a latent disease?
a. Hepatitis C b. Herpes simplex c. Epstein-Barr virus d. Varicella virus
Answer: a. Each of these will cause a latent disease except for hepatitis C, which lends itself to chronic infections rather than latent disease.
179. What is not true of virulence of an organism?
a. An organism is either virulent or not virulent. b. Virulence occurs in pathogens, while not all pathogens are very virulent. c. Virulence involves the median lethal dose of an organism. d. Virulence can be determined in animal models.
Answer: a. Virulence is actually a continuum rather than an all or none phenomenon. The rest of the statements on virulence are all true.
180. The difference between a primary pathogen and an opportunistic pathogen depends mostly on what factor or factors?
a. Virulence of the organism b. Host factors c. Type of organism d. Incubation period of the infection
Answer: b. Opportunistic pathogens differ from primary pathogens because of host factors, that will protect the healthy person from an opportunistic infection but not necessarily a primary pathogenic infection.
181. What portal of entry is not related to the mucous membranes?
a. Gastrointestinal tract b. Vaginal c. Needle injection d. Respiratory tract
Answer: c. Each of these is a mucous membrane portal of entry except for a needle injection, which is a parenteral portal of entry.
182. Which is not considered a TORCH infection, capable of vertical transmission from mother to fetus in utero?
a. Rubella b. HIV c. Hepatitis B d. Hepatitis A
Answer: d. The diseases listed include TORCH infections, except for hepatitis A, which is not transmitted this way.
183. What type of infection will involve most or all of the person’s organs and tissues?
a. Primary infection b. Secondary infection c. Focal infection d. Systemic infection
Answer: d. A systemic infection involves most or all of the person’s organs or tissues, leading to what becomes a systemic disease.
184. What type of organism will have a protein or glycoprotein adhesin on fimbriae as part of its virulence factor?
a. Virus b. Bacteria c. Helminth d. Protozoan
Answer: b. Bacteria will have adhesins made from proteins or glycoproteins on fimbriae that bind to receptors on the host cell.
185. What is the operative definition of toxemia?
a. The presence of bacterial toxins in the bloodstream b. The presence of bacteria in the bloodstream c. The state of shock that comes with a severe infection d. The multiplication of an organism in the blood
Answer: a. Toxemia in particular means that toxins are present in the bloodstream. It does not necessarily mean there are bacteria, shock, or organism multiplication in the blood itself.
186. What is the major difference between an endotoxin and an exotoxin?
a. Endotoxins are heat labile and exotoxins are heat stable b. Exotoxins cause inflammatory responses and endotoxins cause specific host responses c. Exotoxins are far more lethal than endotoxins d. Endotoxins are made from proteins and exotoxins are made from lipids
Answer: c. Each of these statements is false except that exotoxins are far more lethal in smaller quantities when compared to endotoxins.
187. Which virulence factor in bacteria will break down antibodies in order to prevent phagocytosis?
a. Capsules b. Fimbriae c. Proteases d. Phospholipases
Answer: c. Bacteria can contain proteases that break down antibodies, which in turn prevents the phagocytic process.
188. What happens in viruses most often to help the virus be more infective to the host?
a. Toxin production b. Formation of capsules around the virus c. Protease synthesis d. Antigenic variation
Answer: d. Viruses undergo antigenic variation in order to change themselves in order to be able to infect a host cell. They do not make toxins, capsules, or proteases.
189. What is not a toxin produced by Aspergillus as part of its virulence factors?
a. Elastase b. Ergot toxin c. Aflatoxin d. Gliotoxin
Answer: b. Each of these, plus catalase, is made by Aspergillus as part of its virulence; however, ergot toxin is made by another fungus that grows on rye.
190. What represents the percent of people who die of a disease compared to a standard number in the population?
a. Mortality rate b. Morbidity rate c. Prevalence d. Incidence
Answer: a. The mortality rate is a percentage that is the number of patients who die of a disease compared to a standard number in the population.
191. What is the responsibility of goblet cells in the innate immune system?
a. They make mucus b. They secrete immunoglobulins into the GI and respiratory tract c. They cause increased inflammation if there are pathogens present d. They contain cilia that drive off debris and pathogens
Answer: a. Goblet cells make mucus by secreting it from secretory vesicles. The mucus helps trap debris and pathogens before they can invade.
192. What is not a mechanical defense system in the eyes?
a. Blinking b. Tears c. Cilia d. Eyelashes
Answer: c. Each of these is a mechanical defense mechanism in the eyes, except there are no cilia in the eyes that act as a defense system in this area.
193. What aspect of the innate immune system is disrupted by taking an antibiotic?
a. Cilia movement b. Chemical barriers c. Immunoglobulins d. Microbiome
Answer: d. The microbiome is disrupted when antibiotics are taken, which keeps these organisms from preventing an opportunistic infection.
194. What is least likely a factor with the sebum produced by sebaceous glands to prevent bacterial contamination of the skin?
a. It supports the growth of a healthy microbiome. b. It contains antibodies that are directed at pathogens. c. It seals off the hair follicle. d. It is the source of acidic oleic acid.
Answer: b. Each of these is a reason why sebum is protective against pathogens but it does not contain any antibodies directed at pathogens.
195. What is not something that antimicrobial peptides do in the innate immune system?
a. The destroy nucleic acids. b. They damage the cell membrane. c. They bind iron. d. The prevent cell wall synthesis.
Answer: c. Each of these is something that antimicrobial peptides do but they do not bind iron as one of their properties.
196. Where are most of the antimicrobial peptides made and used?
a. Skin b. Blood c. Lymph glands d. Mouth
Answer: a. Most of the antimicrobial peptides are made and used by the skin. These act as chemical protection against different pathogens.
197. Where can you find acute-phase proteins in the innate immune system?
a. Bone marrow b. Lymph nodes c. Epithelial surfaces d. Blood plasma
Answer: d. Acute-phase proteins have antimicrobial properties and are found in blood plasma as part of the innate immune response.
198. The coating of bacteria with a substance to help kill it is called what?
a. Forming a membrane attack complex b. Phagocytosis c. Opsonization d. Complement activation
Answer: c. The coating of bacteria with a substance that assists in its recognition by the phagocytic cells is called opsonization.
199. The MAC or membrane attack complex is active against what type of pathogen?
a. Viruses b. Gram-positive bacteria c. Gram-negative bacteria d. Fungi or yeast
Answer: c. Gram negative bacteria are the only pathogens affected by the MAC because it causes pores to be made into the membranes of these cells.
200. What type of proteins are interleukins, interferons, and chemokines?
a. Enzymes b. Structural antibody proteins c. Complement proteins d. Cytokines
Answer: d. These proteins are cytokines that have different effects on the immune system, most of which are stimulatory in nature.
201. Which molecules are directly responsible for increasing the person’s body temperature in an infection?
a. Bradykinins b. Prostaglandins c. Histamines d. Interferons
Answer: b. Prostaglandins are most involved in raising body temperature, which impacts the growth of microorganisms.
202. Which is not a type of granulocyte?
a. Lymphocyte b. Neutrophil c. Eosinophil d. Basophil
Answer: a. Each of these is a granulocyte because they contain granules, except for lymphocytes, which do not contain granules.
203. What is not something that natural killer cells do to kill off damaged cells?
a. Trigger target cell apoptosis b. Phagocytize target cells c. Cause pores in the target cell d. Release granzymes to damage cells
Answer: b. NK cells are active against damaged cells. They do each of these things except they do not participate in phagocytosis.
204. What chemical mediator is responsible for the vasodilation that happens because of the inflammatory response?
a. Histamine b. Interferon c. Cytokines d. Interleukin
Answer: a. The release of histamine from mast cells causes vasodilation that ultimately dilutes the bacteria or toxins and allows for inflammatory cells to reach the site of the infection.
205. Where does extravasation of white blood cells occur?
a. Arteries b. Lymph nodes c. Capillaries d. Veins
Answer: c. Extravasation or diapedesis occurs only in the capillaries because they have very thin walls and also have low levels of turbulence so the white blood cells can easily attach to the endothelial lining and pass between adjacent cells.
206. What least likely attaches to the pathogen as part of opsonization?
a. Complement proteins b. Cytokines c. Lectin d. Antibodies
Answer: b. Opsonization or the addition of opsonin to a pathogen involves lectin, antibodies, and some complement proteins. These will increase the chances of phagocytosis.
207. Which substance does not participate in destroying a pathogen inside a phagocyte?
a. Hydrogen peroxide b. Reactive oxygen species c. Complement proteins d. Lysosomal enzymes
Answer: c. Inside the phagocyte, there are lysosomal enzymes, hydrogen peroxide, and reactive oxygen species that participate in digesting the pathogen. Complement proteins are not involved.
208. What molecule type is too small to initiate an immune response in the body by itself but is able to cause an immune response if bound to something bigger?
a. Hapten b. Epitope c. Antigen d. Conjugate antigen
Answer: a. A hapten is a small molecule that is too small to initiate an immune response by itself. If bound to a larger protein, it forms a conjugate antigen that will be antigenic.
209. What part of the antibody is directly involved in binding to the antigen?
a. Fc region b. Constant region c. Disulfide bond d. Variable region
Answer: d. The variable region is part of the Fab region that actually does the binding of the antigen to the antibody.
210. What is not true of an antigen presenting cell?
a. They are all capable of making antibodies. b. They can be macrophages, B cells, or dendritic cells. c. They are the only cells that express MHC II. d. They engulf antigens and re-present them on their surface.
Answer: a. Each of these is true of an antigen presenting cell, which may or may not produce antibodies, depending on which type of cell it is. Only the B cells make antibodies; dendritic cells and macrophages do not do this.
