Portage Learning Microbiology. Final Exam

Question 9

Portage Learning Microbiology. Final Exam. How do cofactors influence enzyme activity?

• They break down enzymes after each reaction
• They stop enzymatic reactions completely
• They activate enzymes, allowing catalysis to occur
• They permanently alter an enzyme’s structure

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Question 10

What happens when a phosphate group is removed from ATP?

• It releases energy and converts into ADP
• It becomes AMP (adenosine monophosphate)
• It gains energy and forms a new ATP molecule
• It loses its ability to participate in metabolism

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Question 11

Which phosphorylation process directly transfers a phosphate group from a reactive intermediate to ADP?

• Chemophosphorylation
• Oxidative phosphorylation
• Substrate-level phosphorylation
• Photophosphorylation

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Question 12

Bacteria must develop entirely new metabolic pathways to process alternative sugars.

• True
• False

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Question 13

What happens to non-glucose molecules in metabolism?

• They are excreted as waste
• They directly enter the electron transport chain
• They are converted into intermediates that enter glycolysis or the Krebs cycle
• They are stored indefinitely as they cannot be used for energy

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Question 14

Which of the following best describes photosynthesis?

• The breakdown of chlorophyll to release oxygen
• The storage of excess energy in animal cells Portage Learning Microbiology. Final Exam
• The process by which plants capture sunlight to produce ATP and NADPH
• The conversion of glucose into ATP in mitochondria

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Question 15

Which macromolecule produces more ATP than glucose when metabolized? Portage Learning Microbiology. Final Exam

• Lipids (or Fats / Triglycerides)

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Question 16

A scientist is studying a new strain of bacteria that thrives in nutrient-rich environments. She observes that when exposed to a high concentration of polysaccharides, the bacteria rapidly break them down into simple sugars and use them for energy production. However, in a low-nutrient environment, the bacteria shift their metabolism to synthesize essential macromolecules needed for survival. Explain the significance of metabolic balance between catabolism and anabolism in microbial survival.

• The metabolic balance between catabolism and anabolism allows bacteria to dynamically adapt to fluctuating environmental conditions while maintaining cellular homeostasis. In nutrient-rich environments, catabolic pathways break down complex polysaccharides into simple sugars, releasing energy in the form of ATP and generating precursor metabolites. Conversely, when nutrients are scarce, the cell shifts toward anabolic pathways, utilizing stored ATP and raw materials to synthesize essential macromolecules needed for structure and survival. This balance ensures resource conservation and metabolic flexibility; without it, bacteria would either deplete their resources during starvation or fail to efficiently harvest energy when food is abundant, leading to cell death.

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Question 17

How does contrast influence the visibility of an object?

• Contrast has no effect on visibility
• Lower contrast makes an object easier to see
• Higher contrast makes an object easier to see
• Higher contrast decreases resolution

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Question 18

Which part of a microscope helps regulate the brightness of the image?

• Objective lens
• Iris diaphragm
• Coarse focus knob
• Condenser

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Question 19

Which of the following best explains why unstained cells are difficult to see under bright field microscopy?

• The light used in microscopy destroys unstained cells
• They lack sufficient contrast due to their flat and transparent nature
• Their structures are naturally too dark to observe without staining
• They are too small to be detected by any microscope Portage Learning Microbiology. Final Exam

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Question 20

What is a limitation of electron microscopy?

• It produces images with lower resolution than light microscopy
• It can only be used to view large specimens
• It requires samples to be fixed and may alter cell structure
• It does not require any special sample preparation

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Question 21

Match the microscope to the type of organism or specimen you could identify using it.

• Bacteria and small microorganisms → Brightfield
• Live cells, such as amoeba or protozoa → Phase contrast
• Viruses and subcellular structures → Electron
• Unstained, transparent cells or structures in high contrast → Dark field
• Fluorescently tagged proteins or specific cellular components → Fluorescence
• Tissues or organisms that have been stained or fixed → Confocal

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Question 22

Which of the following is NOT a characteristic of wet mount preparations?

• Live specimens are observed
• The sample is covered with a glass coverslip
• Motility and behavior of the microorganism can be seen
• Heat fixation is applied

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Question 23

In acid-fast staining, carbolfuchsin is used as the counterstain to differentiate between acid-fast and non-acid-fast bacteria.

• True
• False

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Question 24

Explain how Gram-positive and Gram-negative bacteria differentiate during the Gram staining procedure based on their cell wall structures.

• Gram-positive and Gram-negative bacteria stain differently because of structural differences in their cell walls. Gram-positive bacteria possess a thick layer of peptidoglycan which shrinks and dehydrates during the alcohol wash, trapping the primary crystal violet-iodine complex inside to make the cells look purple. Gram-negative bacteria possess a much thinner layer of peptidoglycan surrounded by an outer lipopolysaccharide membrane. The alcohol dissolves this lipid outer layer and leaves pores in the thin peptidoglycan layer, causing the primary dye to completely wash out. The cells are then colored by the counterstain (safranin), making them look pink or red.

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Question 25

Which of the following best describes selective media?

• It eliminates the need for antibiotics in medical samples
• It is only used for growing fungi
• It enhances the growth of all microbes
• It contains additives that inhibit unwanted microbial growth

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Question 26

Which of the following properties can be differentiated using differential media?

• Differences in lactose fermentation or other metabolic activities

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Question 27

Which type of media contains ingredients like yeast extract, where the exact chemical composition is unknown?

• Chemically defined media
• Reducing media
• Complex media
• Enriched media

Question 27

Which of the following is true about enriched media?

• It lacks essential nutrients for bacterial survival
• It can be a combination of selective, differential, and enriched media
• It is only used for Gram-positive bacteria
• It completely prevents microbial growth

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Question 28

The process of plating involves spreading a bacterial culture onto agar using a non-sterile loop.

• True
• False

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Question 29

The goal of the quadrant streak method is to generate a pure culture, free from outside contaminants.

• True Portage Learning Microbiology. Final Exam
• False

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Question 30

What does modifying the number of phases and loop passes in a dilution streak allow researchers to do?

• Prevent colony formation by diluting the sample too much
• Ensure that no colonies grow on the agar plate
• Optimize the growth of individual colonies based on the concentration of the starting culture
• Increase the concentration of bacteria on the agar plate

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Question 31

Which of the following statements best describes the differences between the quadrant growth plate, spread plate, and pour plate techniques?

• The spread plate and pour plate both allow bacterial growth only on the agar surface, while the quadrant streak plate isolates mixed cultures.
• The quadrant growth plate is best for counting bacterial colonies, while the spread plate and pour plate are used only for anaerobic bacteria.
• The quadrant growth plate is used to isolate four different cultures, the spread plate evenly distributes a liquid sample on the surface, and the pour plate embeds bacteria within the agar.
• The pour plate is primarily used for isolating pure colonies, while the quadrant streak and spread plates are used for counting bacterial cells.

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Question 32

After performing a quadrant streak on MacConkey agar, a researcher observes bacterial growth only in the first phase (P1), with no visible colonies in the later phases. What could be the reason for this outcome, and how does the quadrant streaking method help in isolating bacteria?

Correct Answer:

• Reasons for growth only in P1: The researcher may have missed dipping or dragging the loop into the P1 area when transitioning to Phase 2. Alternatively, the inoculation loop may have been too hot during flame sterilization between phases, killing the transferred bacteria. A very low initial culture concentration could also result in all available cells being deposited entirely within the first quadrant.
• How it helps isolate bacteria: The quadrant streak uses mechanical dilution. By sequentially spreading a fraction of the bacteria across fresh sections of agar and sterilizing the loop between phases, the cell concentration drops. By the final quadrants, individual cells are deposited far enough apart to grow into isolated, pure colonies.

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Question 33

Which of the following best explains why antibodies produced against Streptococcus can damage heart tissue during rheumatic fever?

• Heart tissue antigens resemble Streptococcus antigens, leading to cross-reactivity.
• The infection spreads directly into the bloodstream.
• Heart valves are colonized by the bacteria.
• Antibodies are too weak to fight off the infection.

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Question 34

What skin infection caused by Staphylococcus aureus is characterized by pus-filled lesions in the hair follicles?

• Scalded skin syndrome
• Impetigo
• Folliculitis
• Psoriasis

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Question 35

According to the CDC, which of the following activities does NOT spread tuberculosis (TB)?

• Sneezing in crowded spaces
• Sharing a beverage
• Inhaling airborne droplets
• Coughing in close quarters Portage Learning Microbiology. Final Exam

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Question 36

What organism causes leprosy (Hansen’s disease)?

• Mycobacterium leprae
• Mycobacterium tuberculosis
• Streptococcus pyogenes
• Staphylococcus aureus

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Question 37

Bubonic plague is best characterized by painfully swollen lymph nodes.

• True
• False

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Question 38

A baby born to an untreated mother with chlamydia may develop which condition?

• Ophthalmia neonatorum
• Neonatal pneumonia
• Meningitis
• Scarlet fever

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Question 39

A 60-year-old farmer sustains a deep puncture wound from a rusty nail. Days later, he develops muscle stiffness and spasms, beginning with lockjaw. In a few sentences, name the causative organism, explain how it causes disease, and how it can be prevented.

Correct Answer:

• Causative Organism: Clostridium tetani.
• Mechanism: The tissue injury introduces anaerobic bacterial spores which germinate and secrete the neurotoxin tetanospasmin. This blocks inhibitory neurotransmitters, driving unrelenting muscle spasms and rigid contraction.
• Prevention: Standard routine immunization via the tetanus vaccine (DTaP/Tdap/Td). Deep or dirty wounds require immediate passive immunity via tetanus immune globulin (TIG) if vaccine records are unverified.

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Question 40

A 22-year-old college athlete develops a painful, red, swollen lesion on his leg that resembles a “spider bite.” The lesion is warm to the touch and filled with pus. He lives in a dormitory and shares athletic equipment with teammates. A wound culture reveals Gram-positive cocci in clusters. In a few sentences, identify the infection, the causative organism, and why this strain is particularly concerning.

Correct Answer:

• Identity & Organism: Methicillin-Resistant Staphylococcus aureus (MRSA) skin infection.
• Why it is concerning: It possesses strong structural resistance to conventional beta-lactam class antibiotics, limiting therapeutic options. It also readily spreads inside community settings through casual contact or shared items, causing deep tissue damage if untreated.

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Question 41

Which example illustrates the diversity in viral genome size?

• Poliovirus and Pandoravirus
• Eukaryotic mitochondria and chloroplast DNA
• Bacteria with plasmids
• Prokaryotic cells with circular DNA and eukaryotic cells with linear DNA

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Question 42

At which point does viral genome replication begin?

• As soon as the virus encounters the host membrane
• After attachment and entry into the host cell
• Immediately after the virus exits the previous host cell
• Before the virus attaches to the host cell

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Question 43

A pregnant woman contracts rubella. Her obstetrician tells her there is no risk to the fetus because the virus cannot cross the placenta. True or False?

• True
• False

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Question 44

Which statement correctly describes measles transmission?

• It is spread only through contaminated food or water
• It is transmitted via airborne particles that can remain in the air for up to 2 hours
• It is transmitted only through blood exposure
• It is spread only through direct contact with skin lesions Portage Learning Microbiology. Final Exam