Biology, HSSC-KPK First Year. This chapter is split into 21 topics and has
546 practice questions. The topics covered are listed below, followed by
10 free sample questions from the chapter.
Topics in this chapter
Taxonomy, Phylogeny & Archaea30 questions
Classification of Bacteria30 questions
Structure of Bacterial Cell30 questions
Size, Shape & Endospores30 questions
Nutrition & Photosynthesis in Bacteria30 questions
Bacterial Flora & Control of Harmful Bacteria30 questions
Bacterial Cell Parts Shown in Fig 6.123 questions
Bacterial Shapes Shown in Fig 6.220 questions
Endospore Structure and Survival20 questions
Griffith Transformation Experiment in Fig 6.621 questions
Transduction and Conjugation Steps in Figs 6.7 and 6.823 questions
Bacterial Growth Curve and Generation Time Calculations22 questions
Photosynthetic Bacteria Compared with Cyanobacteria21 questions
Archaea Compared with Bacteria21 questions
Bacterial Diseases of Humans Compared23 questions
Bacterial Plant Diseases Compared22 questions
Sample questions: Prokaryotes
10 sample questions with the correct answer and an explanation. Try to answer each one before reading the explanation.
Q1. Which statement correctly integrates the major groups of bacteria with their diagnostic features?
A. Proteobacteria (Gram-negative, five subgroups), Chlamydias (parasitic Gram-negative), Spirochetes (helical, internal filament movement), Gram-positive bacteria (including actinomycetes), and Cyanobacteria (oxygen-producing photosynthetic bacteria) together represent the major diagnostic groupings of bacteria(correct answer)
B. All bacteria belong to a single undivided group with no distinguishing features
C. Cyanobacteria and Chlamydias are the same group under different names
D. Proteobacteria and Spirochetes are identical in structure and function
Answer: A.The chapter organizes bacteria into major groups distinguished by clear diagnostic features: proteobacteria (Gram-negative, five metabolically distinct subgroups), chlamydias (parasitic Gram-negative), spirochetes (helical, moving via internal filaments), Gram-positive bacteria (including antibiotic-producing actinomycetes), and cyanobacteria (oxygen-producing photosynthetic bacteria).
Q2. Which statement best explains why cyanobacteria are considered the most prominent of the photosynthetic bacteria?
A. They are found only in extreme environments
B. They are the only bacteria capable of any form of photosynthesis
C. Their oxygen-producing photosynthesis permanently transformed Earth's atmosphere and enabled the evolution of other aerobic life(correct answer)
D. They are the largest bacteria known
Answer: C.Cyanobacteria are considered the most prominent photosynthetic bacteria because their oxygen-producing photosynthetic activity permanently transformed Earth's atmosphere (raising oxygen from 1% to 21%) and, through the resulting ozone layer, enabled the evolution and survival of other aerobic autotrophs.
Q3. The semi-fluid, jelly-like portion of cytoplasm enclosed by the cell membrane, excluding membrane-bound organelles (which bacteria lack), is called:
A. Cytosol(correct answer)
B. Nucleoid
C. Mesosome
D. Capsule
Answer: A.Cytoplasm is a gelatinous mass of proteins, carbohydrates, lipids, nucleic acids, salts and inorganic ions dissolved in water, and lacks membrane-bound organelles; the semi-fluid jelly-like portion of cytoplasm enclosed by the cell membrane is called cytosol.
Q4. Which statement correctly integrates the structure of the bacterial cell envelope from outside to inside?
A. The nucleoid lies outside the cell wall, while the capsule is found inside the cytoplasm
B. Ribosomes form the outermost boundary of the bacterial cell
C. Cell membrane is the outermost layer, followed by the capsule, then the cell wall, then the cytoplasm
D. Capsule (outermost, protective) -> cell wall (peptidoglycan, shape-giving) -> cell membrane (selectively permeable, with mesosomes) -> cytoplasm (containing ribosomes and the nucleoid)(correct answer)
Answer: D.From outside to inside, a typical bacterial cell is organized as: capsule (protective, outermost) -> cell wall (peptidoglycan, giving shape) -> cell membrane (selectively permeable, forming mesosomes) -> cytoplasm (containing ribosomes and the nucleoid with the chromosome and plasmids).
Q5. Which statement correctly explains the survival advantage that endospore formation provides to Gram-positive bacteria?
A. Endospores are more vulnerable to environmental stress than the normal vegetative cell
B. Endospore formation doubles the number of bacterial cells immediately
C. By becoming a dehydrated, thickly protected, dormant structure, the endospore can survive extreme heat, radiation, and water shortage that would kill the normal vegetative cell, later germinating when conditions improve(correct answer)
D. Endospores make bacteria permanently immune to all antibiotics, with no relation to environmental stress
Answer: C.Because the endospore contains little water and is protected by thick peptidoglycan layers, it is a highly resistant, dormant structure able to survive extremely harsh conditions of temperature, radiation, and water shortage; when the environment becomes favourable again, the protective layers break down and it is released as a vegetative cell.
Q6. Which statement correctly integrates the classification of bacteria by nutrition (autotrophic vs heterotrophic) with their photosynthetic mechanism (in the autotrophic photosynthetic bacteria)?
A. Autotrophic photoautotrophs use light energy (via bacteriochlorophyll and photosystem I only) with H2S as the hydrogen source, releasing sulphur rather than oxygen, distinguishing them from the oxygen-releasing, water-splitting photosynthesis of cyanobacteria and plants(correct answer)
B. Heterotrophic bacteria perform photosynthesis using bacteriochlorophyll, just like photoautotrophs
C. All autotrophic bacteria, whether photoautotrophic or chemoautotrophic, use exactly the same photosynthetic mechanism as plants
D. Chemoautotrophs use bacteriochlorophyll to capture solar energy, just like photoautotrophs
Answer: A.Photoautotrophic bacteria are one branch of autotrophic nutrition; their photosynthesis (bacteriochlorophyll, photosystem I only, cyclic electron flow) uses hydrogen sulphide instead of water, releasing sulphur rather than oxygen, which distinguishes bacterial photosynthesis from the oxygen-releasing, water-splitting photosynthesis of cyanobacteria and plants.
Q7. What puzzled Griffith and his associates was that a mixture of heat-killed S-type and live R-type bacteria, injected into a healthy mouse, caused the mouse to die from pneumonia. The autopsy revealed the presence of:
A. Only R-type cells, with no S-type cells present
B. Many living S-type cells in the dead body of the mouse(correct answer)
C. No bacteria at all in the mouse's body
D. A completely new species of bacteria
Answer: B.A mixture of heat-killed S-type and live R-type was injected into a healthy mouse, which died from pneumonia; the autopsy revealed the presence of many living S-type cells in the dead body of the mouse, even though only heat-killed S-type cells had been injected.
Q8. In a classic experiment, two E. coli mutants (one unable to synthesize biotin and methionine, the other unable to synthesize threonine and leucine) were mixed and cultured in a medium lacking all four essential compounds. Hundreds of colonies developed, even though neither mutant alone could grow without these chemicals. This result suggests:
A. The culture medium had somehow been contaminated with all four missing compounds
B. Exchange of genes occurred between the two parental bacteria, forming new recombinants that no longer required the four essential compounds(correct answer)
C. Both mutant strains had spontaneously reverted to the wild type with no genetic exchange
D. No bacteria actually grew, and the observation was a laboratory error
Answer: B.This surprising growth of hundreds of colonies suggests that exchange of genes occurred between the two parental bacteria, and new recombinants were formed which did not require the four essential compounds for growth, providing early evidence for bacterial conjugation.
Q9. Later studies using the electron microscope confirmed the close contact and the formation of a conjugation tube between the parental cells in the experiment described above. This confirmed that the new recombinants arose through:
A. Uptake of free DNA from the environment (transformation)
B. Transfer of DNA via a bacteriophage (transduction)
C. Random spontaneous mutation with no contact required
D. Direct physical contact and DNA transfer between the two bacterial strains (conjugation)(correct answer)
Answer: D.Electron microscope studies confirmed the close contact and the formation of a conjugation tube between the parental cells, confirming that the new recombinants arose through direct physical contact and DNA transfer, i.e., conjugation, rather than transduction or transformation.
Q10. Which statement correctly distinguishes the three methods of bacterial genetic recombination?
A. Conjugation is the only method that does not involve a donor and recipient cell
B. All three methods require the exact same conjugation tube structure
C. Transformation involves uptake of free DNA released by a donor; transduction uses a bacteriophage as an intermediary; conjugation requires direct cell-to-cell contact via a conjugation tube(correct answer)
D. Transformation and transduction both require direct cell-to-cell contact, unlike conjugation
Answer: C.The three recombination methods are mechanistically distinct: transformation involves a recipient taking up free DNA released by a donor (no intermediary or contact needed), transduction uses a bacteriophage to carry DNA between cells, and conjugation requires direct physical contact between donor and recipient via a conjugation tube.