Free Kingdom Prokaryotae MCQs with Answers

1. Select a method which causes the oxidation of chemical constituent of a bacterial cell:

• A. Steam
• B. Dry heat
• C. Filtration
• D. Radiation

Explanation: Dry heat helps kill the organisms using the destructive oxidation method. This helps destroy large contaminating bio-molecules such as proteins. The essential cell constituents are destroyed and the organism dies. The temperature is maintained for almost an hour to kill the most difficult of the resistant spores.

2. All of the following are examples of substances found in bacteria or archaea except:

• A. Peptidoglycans
• B. Flagellin
• C. Bacteriorhodopsin
• D. Chitin
• E. Phycobilins

Explanation: Chitin is a polysaccharide found in the exoskeleton of arthropods and in the cell walls of fungi. Flagellin is the protein of bacterial flagella. Bacteriorhodopsin is a photosynthetic pigment found in extreme halophiles. Phycobilins are photosynthetic pigments found in cyanobacteria (as well as in red algae).

3. Which of the following bacteria are without a cell wall?

• A. Mycoplasma
• B. Gram positive bacteria
• C. Gram negative bacteria
• D. Archaeo bacteria

Explanation: Mycoplasma is indeed a bacterium that is known for lacking a cell wall. Unlike most bacteria, Mycoplasma species do not have a rigid cell wall composed of peptidoglycan. Instead, they have a unique cell membrane that provides shape and protection. This membrane contains sterols, which help maintain structural integrity. The absence of a cell wall makes Mycoplasma cells more flexible and pleomorphic (having various shapes).

4. Gram-negative bacteria are stained pink by the use of:

• A. Crystal violet
• B. Gram's iodine
• C. Feulgen stain
• D. Safranin

Explanation: Option D is correct as gram-negative bacteria are not easily stained by primary dye (crystal violet) so a secondary dye (safranin or fuchsine) is required to dye them a pink or red color.

5. The first simplest oxygen producing organism:

• A. Methanogens
• B. Cyanobacteria
• C. Euglena
• D. Spirogyra

Explanation: There is suggestive evidence that photosynthetic organisms were present approximately 3.2 to 3.5 billion years ago, in the form of stromatolites, layered structures similar to forms that are produced by some modern cyanobacteria.

6. Bacterial pilli help in:

• A. Locomotion
• B. Conjugation
• C. Phagocytosis
• D. Pinocytosis
• E. Exocytosis

Explanation: Conjugative pili allow for the transfer of DNA between bacteria, in the process of bacterial conjugation. They are sometimes called "sex pili", in analogy to sexual reproduction, because they allow for the exchange of genes via the formation of "mating pairs". Locomotion is performed by flagella, phagocytosis, pinocytosis, and exocytosis by microtubules.

7. Which of the following organelles are present in all the bacteria?

• A. Mesosome
• B. Golgi bodies
• C. Mitochondria
• D. Chloroplast

Explanation: Bacteria are prokaryotes. They are made up of single cells. They do not have well-defined nuclei, instead, they possess nucleoids as genetic material. They also lack membrane-bound cell organelles like mitochondria, Golgi bodies, chloroplast, etc. However, they do contain ribosomes and mesosomes in the cytoplasm. Thus, the correct answer is 'Mesosome.'

8. In which of the following growth phases, the number of bacteria increases the most rapidly?

• A. Lag phase
• B. Log phase
• C. Stationary phase
• D. Death/Decline phase

Explanation: The exponential or the log phase is the phase during which the bacterium increases the most rapidly as shown in the figure below:

9. Which of the following bacteria are able to release oxygen into the environment?

• A. Saprotrophic bacteria
• B. Parasitic bacteria
• C. Cyanobacteria
• D. Pathogenic bacteria

Explanation: The answer is tiny organisms known as cyanobacteria or blue-green algae. These microbes conduct photosynthesis using sunshine, water, and carbon dioxide producing carbohydrates and oxygen.

10. Which of the following is true about the structure of a typical bacterium?

• A. It has cell wall
• B. It has cytoplasm
• C. It has genetic material
• D. All of the above

Explanation: A typical bacterium has all the structures listed from opinion A-C, including cell wall, cytoplasm and genetic material. Although some bacterias dont have cell walls, the question asks about a typical bacteria, hence option D is correct. Diagramatic representation of all the structures is given below: