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Basic Microbiology

Prokaryotic Cells Practice Questions

20 free Prokaryotic Cells practice questions for the Microbiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.

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Question 1 of 20 Medium

Which of the following structures is uniquely found in prokaryotic cells and serves as a primary site for genetic material without a surrounding membrane?

  1. A Nucleus
  2. B Nucleoid
  3. C Nucleolus
  4. D Plasmid

Correct answer: Nucleoid

The nucleoid is the irregular-shaped region within a prokaryote that contains all or most of the genetic material. Unlike the eukaryotic nucleus, it lacks a nuclear envelope or membrane.

Question 2 of 20 Medium

What is the primary chemical component of the bacterial cell wall that provides structural rigidity and prevents osmotic lysis?

  1. A Chitin
  2. B Cellulose
  3. C Peptidoglycan
  4. D Lipopolysaccharide

Correct answer: Peptidoglycan

Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane. It is a unique and essential component of most bacterial cell walls.

Question 3 of 20 Medium

In prokaryotic cells, where are the enzymes for the electron transport chain located?

  1. A Mitochondrial inner membrane
  2. B Cytoplasm
  3. C Plasma membrane
  4. D Ribosomes

Correct answer: Plasma membrane

Because prokaryotes lack membrane-bound organelles like mitochondria, they utilize the plasma membrane to house the proteins and enzymes necessary for respiration and energy production.

Question 4 of 20 Medium

Which appendage is primarily used by bacteria for conjugation, or the transfer of DNA between cells?

  1. A Flagellum
  2. B Fimbriae
  3. C Sex pilus
  4. D Capsule

Correct answer: Sex pilus

Pili, specifically sex pili, are hair-like appendages found on the surface of many bacteria that facilitate the attachment and transfer of genetic material during conjugation. Fimbriae are generally used for attachment to surfaces.

Question 5 of 20 Medium

Which of the following describes a 'lophotrichous' flagellar arrangement?

  1. A A single flagellum at one pole
  2. B Flagella distributed over the entire cell surface
  3. C A tuft of several flagella at one pole
  4. D One flagellum at each end of the cell

Correct answer: A tuft of several flagella at one pole

Lophotrichous bacteria carry a tuft of several flagella emerging from a single pole. A lone flagellum at one pole is monotrichous, one flagellum at each end is amphitrichous, and flagella spread over the whole cell surface is peritrichous.

Question 6 of 20 Medium

What is the function of the bacterial capsule?

  1. A Synthesis of membrane proteins
  2. B Protection from phagocytosis
  3. C Active transport of ions
  4. D Storage of calcium ions

Correct answer: Protection from phagocytosis

The capsule is a polysaccharide layer that lies outside the cell envelope, helping the bacteria evade the host immune system by preventing engulfment by white blood cells. It also aids in adherence and protection against desiccation.

Question 7 of 20 Medium

Which ribosomal subunits constitute the 70S ribosome found in prokaryotes?

  1. A 40S and 60S
  2. B 30S and 50S
  3. C 30S and 40S
  4. D 20S and 50S

Correct answer: 30S and 50S

Prokaryotic ribosomes are characterized as 70S, composed of a small 30S subunit and a large 50S subunit. This differs from eukaryotic 80S ribosomes, making them a target for certain antibiotics.

Question 8 of 20 Medium

What is the primary role of endospores in bacteria such as Bacillus and Clostridium?

  1. A Reproduction and dispersal
  2. B Enhanced motility in viscous fluids
  3. C Survival in harsh conditions
  4. D Increasing the rate of nutrient uptake

Correct answer: Survival in harsh conditions

Endospores are highly resistant, dormant structures formed in response to adverse conditions like nutrient depletion or extreme heat. They are not reproductive structures, as one cell produces only one endospore.

Question 9 of 20 Medium

Which of the following is true regarding Gram-negative bacteria?

  1. A They have a thick layer of peptidoglycan.
  2. B They lack an outer membrane.
  3. C Their outer membrane contains LPS.
  4. D They appear purple after a Gram stain.

Correct answer: Their outer membrane contains LPS.

Gram-negative bacteria possess a thin peptidoglycan layer and an outer membrane containing lipopolysaccharides (LPS), which act as endotoxins. They appear pink or red after Gram staining due to the safranin counterstain.

Question 10 of 20 Medium

Which prokaryotic structure contains high concentrations of calcium and dipicolinic acid?

  1. A Capsule
  2. B Endospore
  3. C Cell wall
  4. D Flagellum

Correct answer: Endospore

The core of an endospore contains calcium complexed with dipicolinic acid, which represents about 10% of the spore's dry weight. This complex plays a vital role in maintaining dormancy and heat resistance.

Question 11 of 20 Medium

Plasmids are defined as:

  1. A Segments of RNA used for protein synthesis.
  2. B Extrachromosomal, circular DNA molecules.
  3. C The site of ATP production in the cytoplasm.
  4. D Protein structures used for attachment.

Correct answer: Extrachromosomal, circular DNA molecules.

Plasmids are small, circular, double-stranded DNA molecules that are distinct from a cell's chromosomal DNA. They often carry genes that provide a selective advantage, such as antibiotic resistance.

Question 12 of 20 Medium

Which of the following inclusions helps aquatic bacteria maintain buoyancy at specific depths?

  1. A Metachromatic granules
  2. B Magnetosomes
  3. C Lipid inclusions
  4. D Gas vacuoles

Correct answer: Gas vacuoles

Gas vacuoles are protein-shelled cylinders that contain gas, allowing aquatic prokaryotes to regulate their buoyancy and position themselves in the water column for optimal light or nutrients.

Question 13 of 20 Medium

What occurs during the process of binary fission?

  1. A The cell undergoes meiosis to produce gametes.
  2. B The cell divides to produce two identical daughter cells.
  3. C Two cells fuse to exchange genetic information.
  4. D A small bud forms and eventually detaches from the parent cell.

Correct answer: The cell divides to produce two identical daughter cells.

Binary fission is the primary method of asexual reproduction in prokaryotes. The cell grows, duplicates its genetic material, and then splits into two genetically identical units.

Question 14 of 20 Medium

Which component is missing in the cell walls of Archaea compared to Bacteria?

  1. A Lipids
  2. B Proteins
  3. C Polysaccharides
  4. D Peptidoglycan

Correct answer: Peptidoglycan

Archaea do not contain peptidoglycan in their cell walls; instead, many have a similar substance called pseudopeptidoglycan (pseudomurein) or consist of S-layers made of proteins.

Question 15 of 20 Medium

What is the function of the periplasmic space in Gram-negative bacteria?

  1. A Storage of energy in the form of starch.
  2. B Anchoring point for the flagellar motor.
  3. C Regulation of osmosis by excluding all salts.
  4. D Contains enzymes for nutrient processing.

Correct answer: Contains enzymes for nutrient processing.

The periplasm is the region between the inner and outer membranes in Gram-negative bacteria. It contains various enzymes and proteins involved in nutrient transport, processing, and cell wall synthesis.

Question 16 of 20 Medium

Which statement accurately describes bacterial chemotaxis?

  1. A Movement toward or away from chemicals.
  2. B Movement toward a light source.
  3. C Passive drifting in a concentration gradient.
  4. D The process of absorbing chemical nutrients.

Correct answer: Movement toward or away from chemicals.

Chemotaxis is the directed movement of a motile cell toward a chemical attractant (positive) or away from a repellent (negative) by altering the frequency of 'runs' and 'tumbles'.

Question 17 of 20 Medium

Which group of bacteria is characterized by having an axial filament (endoflagella) for motility?

  1. A Bacilli
  2. B Coccobacilli
  3. C Vibrios
  4. D Spirochetes

Correct answer: Spirochetes

Spirochetes possess axial filaments, which are bundles of fibrils that arise at the ends of the cell beneath an outer sheath. Their rotation causes the whole cell to move in a corkscrew-like motion.

Question 18 of 20 Medium

What are 'metachromatic granules' (volutin) used for in a prokaryotic cell?

  1. A Inorganic phosphate storage
  2. B Storage of glycogen
  3. C Photosynthesis
  4. D Chromosomal DNA replication

Correct answer: Inorganic phosphate storage

Metachromatic granules are inclusions that store inorganic phosphate, which can be used for ATP synthesis. They are called 'metachromatic' because they stain red with certain blue dyes.

Question 19 of 20 Medium

Teichoic acids are a unique component of the cell wall in which type of bacteria?

  1. A Gram-positive bacteria
  2. B Gram-negative bacteria
  3. C Acid-fast bacteria
  4. D Wall-less bacteria

Correct answer: Gram-positive bacteria

Gram-positive bacteria contain teichoic acids, which are polymers of glycerol or ribitol phosphate. They provide antigenic specificity and help regulate the movement of cations into the cell.

Question 20 of 20 Medium

Which of the following is an example of a prokaryote that naturally lacks a cell wall?

  1. A Mycoplasma
  2. B E. coli
  3. C Staphylococcus aureus
  4. D Mycobacterium

Correct answer: Mycoplasma

Mycoplasma species are unique among prokaryotes because they lack a cell wall. Their plasma membranes are strengthened by sterols, which is unusual for bacteria, to help them resist osmotic lysis.

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