Prokaryotes Test 3

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Question 1:

Which subgroup of proteobacteria does Rhizobium belong to?





Topic: Classification of Proteobacteria

Correct Answer: A) Alpha proteobacteria

Detailed Hint:
  • Proteobacteria are further categorized into several subgroups, with Rhizobium falling under the Alpha proteobacteria subgroup.
  • Rhizobium is known for its symbiotic relationship with leguminous plants, aiding in nitrogen fixation.
  • Therefore, the correct answer is A, "Alpha proteobacteria".

Question 2:

What is the source of hydrogen in photosynthesis for Photoautotrophic bacteria?





Topic: Photosynthesis in Photoautotrophic Bacteria

Correct Answer: B) H2S

Detailed Hint:
  • Unlike plants that utilize water as their hydrogen source during photosynthesis, photoautotrophic bacteria, like cyanobacteria, employ a different strategy.
  • They use hydrogen sulfide as their hydrogen donor in the photosynthesis process.
  • This unique trait leads to the release of elemental sulfur instead of oxygen, a stark contrast to plant photosynthesis.
  • Thus, the correct answer is B, "H2S".

Question 3:

Which organisms are most likely found in extreme environments?





Topic: Extremophiles

Correct Answer: D) Archaea

Detailed Hint:
  • Extreme environments, such as hot springs or deep-sea hydrothermal vents, host a range of unique organisms.
  • Among the options provided, Archaea are the most suited to survive in such extreme conditions.
  • Known as extremophiles, these organisms have adaptations that allow them to thrive where other life forms cannot.
  • Hence, the correct answer is D, "Archaea".

Question 4:

What term is used to describe an extrachromosomal DNA ring in bacteria?





Topic: Bacterial DNA Structures

Correct Answer: B) Plasmid

Detailed Hint:
  • Bacteria possess unique DNA structures beyond their chromosomal DNA.
  • One such structure is a ring-shaped piece of DNA, replicating independently of chromosomal DNA, known as a plasmid.
  • Plasmids often carry genes conferring selective advantages, for instance, antibiotic resistance.
  • Therefore, the correct answer is B, "Plasmid".

Question 5:

Which group of organisms makes the Dead Sea their home?





Topic: Organisms in Extreme Environments

Correct Answer: A) Halophiles

Detailed Hint:
  • The Dead Sea, owing to its extremely high salt concentration, is a hostile environment for most life forms.
  • However, a group of organisms known as Halophiles thrives under these saline conditions.
  • These organisms have evolved mechanisms to maintain their internal salt concentrations, allowing them to survive and multiply.
  • Thus, the correct answer is A, "Halophiles".

Question 6:

What is believed to be the first form of life on Earth?





Topic: Evolution of Life on Earth

Correct Answer: B) Prokaryotes

Detailed Hint:
  • The evolution of life on Earth began with the simplest life-forms.
  • Prokaryotes, organisms devoid of a nucleus and other cellular structures, are widely believed to be the earliest forms of life on Earth.
  • These unicellular organisms laid the groundwork for the development of more complex life forms.
  • Therefore, the correct answer is B, "Prokaryotes".

Question 7:

In bacteria, the phase characterized by the fastest growth is called what?





Topic: Bacterial Growth Phases

Correct Answer: A) Log phase

Detailed Hint:
  • Bacterial growth follows a specific pattern, divided into several phases.
  • The Log phase, also known as the exponential phase, is characterized by rapid, constant, and exponential growth.
  • During this phase, bacteria multiply at their maximum rate, provided environmental conditions are favorable.
  • Hence, the correct answer is A, "Log phase".

Question 8:

What differentiates the genome of prokaryotes from eukaryotes?





Topic: Comparative Genomics

Correct Answer: D) Comprises smaller ribosomes

Detailed Hint:
  • Both prokaryotes and eukaryotes have genomes composed of DNA, not just RNA.
  • The difference lies not in the genetic material but in the ribosomal subunits present in these cells.
  • Eukaryotes possess 60-S and 40-S ribosomal subunits, while prokaryotes have slightly smaller ones, namely 50-S and 30-S.
  • Thus, the correct answer is D, "Comprises smaller ribosomes".

Question 9:

What is the name of the process in which genetic material is transferred from a donor bacterium to a recipient bacterium via a bacteriophage?





Topic: Bacterial Genetic Exchange

Correct Answer: D) Transduction

Detailed Hint:
  • Bacteria have several methods for genetic exchange, including transformation, conjugation, and transduction.
  • In transduction, a bacteriophage, a bacteria-infecting virus, plays a crucial role in transferring DNA from one bacterium to another.
  • Unlike the other options, this process relies on viral intermediaries for genetic exchange.
  • Hence, the correct answer is D, "Transduction".

Question 10:

Which organisms were responsible for first oxygenating the atmosphere?





Topic: Early Earth and Life Evolution

Correct Answer: A) Cyanobacteria

Detailed Hint:
  • The early Earth's atmosphere was initially devoid of oxygen.
  • The first organisms to introduce free oxygen were cyanobacteria, through their photosynthetic activities.
  • While other organisms listed also contribute to the oxygen cycle, none predate cyanobacteria's oxygenic photosynthesis.
  • Therefore, the correct answer is A, "Cyanobacteria".

Question 11:

Which type of cells is peptidoglycan a characteristic feature of?





Topic: Prokaryotic Cell Structure

Correct Answer: B) Bacterial prokaryotic cells

Detailed Hint:
  • The cell wall is an essential component of many cells, serving as a protective barrier.
  • In bacterial prokaryotic cells, a key feature of this wall is peptidoglycan.
  • Eukaryotic cell walls are constructed from different forms of complex carbohydrates, while Archaean prokaryotic cells' walls consist of various polysaccharides and proteins, but lack peptidoglycan.
  • Therefore, the accurate answer is B, "Bacterial prokaryotic cells".

Question 12:

The lipopolysaccharide layer (LPS) is a distinctive element of which type of cell wall?





Topic: Bacterial Cell Wall Diversity

Correct Answer: B) Gram-negative bacteria

Detailed Hint:
  • The cell wall composition can significantly vary across different types of cells.
  • In Gram-negative bacteria, a principal component of the outer membrane is the lipopolysaccharide (LPS) layer.
  • It is primarily located in the outer layer and can be exposed on the cell surface in strains without a protective capsule.
  • Consequently, the correct response is B, "Gram-negative bacteria".
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