Correct Answer: (a)
Tuberculosis is caused by the bacterium Mycobacterium tuberculosis. It primarily affects the lungs and is a major global health challenge requiring long-term antibiotic treatment.
Q2. A bacteria that obtains carbon from the atmosphere and energy and electrons from reduced inorganic compounds is best characterized as a
Correct Answer: (c)
Organisms that obtain carbon from CO2 in the atmosphere are autotrophs. Those that get energy from chemical compounds are chemotrophs, and specifically using inorganic compounds as electron donors makes them 'litho'. Thus, the combination is a chemolithoautotroph.
Q3. H. pylori, a bacteria found in the stomach, produces an enzyme called urease. Urease converts urea in the stomach to ammonia and carbamate. Carbamate is then converted to carbonic acid and another molecule of ammonia. What is the purpose of the production of urease in helping H. pylori survive stomach acid?
Correct Answer: (c)
Ammonia (NH3) is basic. When it reacts with the protons (H+) in the highly acidic stomach environment, it forms ammonium (NH4+), effectively neutralizing the local environment around the bacterium and allowing it to survive.
Q4. Bacteria and archaebacteria may be distinguished based on
Correct Answer: (b)
A fundamental difference between Bacteria and Archaea lies in their membrane lipids. Bacteria have ester-linked lipids (unbranched), while Archaea have ether-linked lipids (often branched), which provides greater stability in extreme environments.
Q5. Gram-positive and gram-negative bacteria are distinguished based on differences in their
Correct Answer: (c)
The Gram stain reaction depends on the cell wall structure. Gram-positive bacteria have a very thick layer of peptidoglycan that retains the crystal violet dye, while Gram-negative bacteria have a much thinner layer of peptidoglycan and an outer lipopolysaccharide membrane.
Q6. The transfer of very specific genes from one bacterium to another by a virus is called
Correct Answer: (c)
In specialized transduction, only specific host genes (those adjacent to the prophage integration site) are transferred when a lysogenic phage excises incorrectly. This is distinct from generalized transduction, where any random segment of host DNA might be packaged into a phage head.
Q7. Which of the following would reduce the pathogenicity of H. pylori?
Correct Answer: (a)
Pathogenicity is the ability to cause disease. H. pylori uses flagella to swim through the thick mucus layer of the stomach to reach the epithelial cells. A mutation that prevents flagella production would render the bacteria unable to reach its target site, significantly reducing its ability to cause infection.
Q8. Why might the actual incidence of an STI be higher than the reported rates?
Correct Answer: (d)
Public health reporting relies on clinical diagnosis and reporting. Social stigma, lack of medical infrastructure, and the marginalized status of high-risk groups all contribute to under-reporting of sexually transmitted infections (STIs).
Q9. Pathogens that kill their hosts too quickly lose the opportunity to spread. Which of the following strategies would promote the spread of a pathogen?
Correct Answer: (d)
Irritation (causing coughing/sneezing) helps aerosolize the pathogen for transmission. Painless sores are effective because the host may not notice the infection and continue to engage in behaviors (like sexual activity) that transmit the pathogen to others.
Q10. Which of the following structures is unique to prokaryotes?
Correct Answer: (a)
Pili (including sex pili for conjugation and attachment pili) are surface appendages found specifically in bacteria. While some eukaryotes have flagella or cell walls, and some produce spores, the structure and protein composition of these differ significantly from those found in prokaryotes.
Q11. A main difference between prokaryotes and eukaryotes is that eukaryotic, but not prokaryotic, cells possess
Correct Answer: (a)
The defining characteristic of eukaryotes is the presence of a membrane-bound nucleus that houses the genetic material. While both groups have cell membranes and ribosomes, and many prokaryotes have cell walls, only eukaryotes possess internal membrane-bound organelles and a nucleus.
Q12. The cell membrane of some photosynthetic bacteria is heavily folded to form membrane invaginations. These folds are used to capture light energy. Which structure–function relationship in the chloroplast of green plants is analogous to the membrane folds?
Correct Answer: (a)
In both cases, the biological strategy is to increase the available surface area for the membrane-bound proteins and pigments (like chlorophyll) involved in light harvesting. In prokaryotes, this is achieved by folding the plasma membrane; in eukaryotes, it occurs in the thylakoid stacks of the chloroplast.
Q13. Some bacteria are capable of forming NH4+ from nitrogen gas in root nodules of leguminous plants. This is best described as a(n)
Correct Answer: (b)
Nitrogen fixation (N2 → NH3/NH4+) is a reduction process. It involves the addition of electrons and hydrogen atoms to the nitrogen atoms to break the strong triple bond of N2 gas.
Q14. During respiration, bacteria can use a greater diversity of electron _____ and _____ than can eukaryotics.
Correct Answer: (d)
While eukaryotes are generally limited to organic electron donors and oxygen as the final electron acceptor, prokaryotes exhibit incredible metabolic diversity, utilizing various inorganic donors (like H2S) and alternative acceptors (like NO3– or SO42–).
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