Free Kingdom Prokaryotae MCQs with Answers

231. Photosythetic bacteria have the ability to release:

• A. Sulphur
• B. Oxygen
• C. Hydrogen
• D. Carbon dioxide

Explanation: Prokaryotes use H2S instead of water so they release sulphur, unlike plants and algae which use water as a hydrogen source and thus release hydrogen.

232. Many bacteria are motile due to the presence of:

• A. Flagella
• B. Pili
• C. Cilia
• D. Microtubules

Explanation: The correct answer is Flagella. Flagella are specialized structures that provide motility to bacteria by rotating like propellers, allowing them to move towards or away from various stimuli. This is a key feature distinguishing motile bacteria from non-motile ones. Other structures like Pili are involved in adhesion rather than movement, Cilia are not present in bacteria, and Microtubules are eukaryotic cell structures unrelated to bacterial motility.

233. The plasma membrane of eukaryotes differ from that of bacteria in having:

• A. Peptidoglycan
• B. Respiratory enzymes
• C. Cholesterol
• D. Phospholipids

Explanation: Cholesterol is a lipid molecule that is an essential component of the plasma membrane in eukaryotic cells. It is primarily found in the animal kingdom, as plants have different types of sterols. Cholesterol plays a crucial role in maintaining the fluidity and stability of the plasma membrane, allowing it to function properly. It helps regulate membrane permeability and protects the membrane from extreme temperatures.

234. Moist heat causes_and kills the microbes:

• A. Oxidation of proteins
• B. Coagulation of proteins
• C. Degeneration of nucleic acids
• D. Bursting up of cells

Explanation: Moist heat primarily kills microbes by causing the coagulation or denaturation of proteins. This process disrupts the protein's three-dimensional structure, leading to the loss of their functional shape, which is crucial for microbial survival. The coagulation of proteins results in the inactivation or destruction of essential microbial enzymes and structures, ultimately leading to cell death. Although moist heat can also cause damage to nucleic acids and, in extreme cases, lead to cell lysis, these are secondary effects. Thus, the coagulation of proteins is the most significant mechanism by which moist heat kills microbes.

235. Pick up the component which is comparatively in greater amount in Gram Negative cell wall:

• A. Lipids
• B. Peptidoglycan
• C. Teichoic acid
• D. Lipoteichoic acid

Explanation: The correct answer is Lipids. Gram-negative bacteria have a unique cell wall structure characterized by an outer membrane rich in lipids, including lipopolysaccharides (LPS), phospholipids, and lipoproteins. This lipid-rich outer membrane provides a protective barrier and plays a significant role in the bacteria's interaction with its environment. In contrast, the peptidoglycan layer in Gram-negative bacteria is much thinner than in Gram-positive bacteria, and teichoic and lipoteichoic acids are absent as they are specific to Gram-positive bacteria.

236. The structure that contains the gene responsible for drug resistance in bacteria is:

• A. Nucleoids
• B. Mesosomes
• C. Chromatin Bodies
• D. Plasmids

Explanation: Plasmids are extrachromosomal DNA found in many bacteria and are known for carrying genes that can provide resistance to antibiotics. This capability makes them crucial for the survival of bacteria in environments with antibiotics. Unlike the nucleoid, which contains the main genetic material of the bacterium, plasmids are smaller DNA structures that can replicate independently and often carry genes beneficial for bacterial adaptation.Nucleoids, mesosomes, and chromatin bodies do not typically carry genes for drug resistance. The nucleoid contains the essential genetic material of the bacterial cell, mesosomes are associated with cell membrane processes, and chromatin bodies are involved in phosphate metabolism, not in storing genetic information for drug resistance.

237. Photosynthetic bacteria utilize H₂S instead of water and liberate one of the following instead of oxygen:

• A. Sulphur
• B. Phosphorus
• C. Calcium
• D. Magnesium

Explanation: Photosynthetic bacteria is mistakenly typed as photosynthesis bacteria. Option A: Sulphur is correct. Photosynthetic bacteria utilize H2S instead of water and liberate sulfur instead of oxygen. CO2 + H20 → (CH2O)n + H2S + 2S STB Pg 105.

238. Bacterial cell wall made up of:

• A. Cellulose & pectin
• B. Cellulose & cutin
• C. Hemicellulose & chitin
• D. Amino acid & sugar

Explanation: Amino acids and sugar is correct.Cell-wall of bacteria is totally different from ordinary plant cell-wall. It is chemically complex and made up of amino acids, sugar and chitin but cellulose is totally missing. The cell-wall of most bacteria have unique macromolecule called peptidoglycan. It is composed of long glycan chains cross-linked with peptide fragments. In addition sugar molecules, teichoic acid, lipoprotein and lipopolysaccharides are also present.STB- Pg 102.

239. Membranous infoldings in bacteria that initiate DNA replication is:

• A. Mesosomes
• B. Peroxisomes
• C. Glyoxysomes
• D. Nucleosomes

Explanation: Mesosomes are invaginations of the cell membrane into the cytoplasm. Mesosomes are in the form of vesicles, tubules, or lamellae. Their function is to help in DNA replication, cell division, respiration, and the export of enzymes.Hence, Option A is correct.STB Pg 102.

240. Mesosomes are the invaginations of which bacterial cell structure?

• A. Cell Wall
• B. Cell Membrane
• C. Plasmid
• D. Cysts

Explanation: Mesosomes were once thought to be infoldings of the plasma membrane found in some bacteria, particularly Gram-positive species, and were believed to play roles in cell division, respiration, DNA replication, and nutrient absorption by increasing the surface area of the cell membrane. They were hypothesized to help anchor the cell division machinery, contain respiratory enzymes, and assist in organizing the bacterial chromosome during replication. However, subsequent research has demonstrated that mesosomes are artifacts resulting from chemical fixation techniques used during electron microscopy sample preparation. Therefore, they are not considered part of the natural structure of bacterial cells.