This set of Microbiology Multiple Choice Questions & Answers (MCQs) focuses on “Structures Internal to the Cell Wall”.
1. Polyisoprenoid branched-chain lipids, are present in which of the following?
c) Archaebacteria and Eubacteria
d) Cannot be determined
Explanation: In Archaebacteria,the lipids are polyisoprenoid branched-chain lipids, in which long-chain branched alcohols(phytanols) are ether linked to glycerol.In Eubacteria,the phospholipids are phosphoglycerides, in which straight-chain fatty acids are ester-linked to glycerol.
2. Cytoplasmic membrane and the cell material bounded by it plus the outer membrane of cell is known as _________
d) Cell membrane
Explanation: A protoplast is that portion of a bacterial cell consisting of the cytoplasmic membrane and the cell material bounded by it. When the cell has two membranes, the cytoplasmic membrane of the protoplast plus the outer membrane of the cell wall, the cell is called a spheroplast rather than protoplast.
3. Which among the following is associated with export of exocellular enzymes?
a) central mesosomes
b) peripheral mesosomes
Explanation: Peripheral mesosomes show only a shallow penetration into the cytoplasm, are not restricted to a central location, and are not associated with nuclear material and they are involved in export of exocellular enzymes such as penicillinase.
4. Ribosomes of prokaryotes have a sedimentation coefficient of?
Explanation: Ribosomes of prokaryotes have a sedimentation coefficient of 70S and are composed of two subunits, a 50S and a 30S subunit. But the ribosomes of eukaryotes have a sedimentation coefficient of 80S and are composed of a 60S and a 40S subunit.
5.Poly-beta-hydroxybutyrate(PHB) present in aerobic bacteria can serve as?
a) a reserve carbon and energy source
b) a reserve source of phosphate
c) acceptor of oxygen
d) provides buoyancy
Explanation: A polymer found in aerobic bacteria, especially under high-carbon,low-nitrogen culture conditions, is a chlorofoam-soluble, lipid like material, poly-beta-hydroxybutyrate(PHB), which can serve as a reserve carbon and energy source.
6. Which among the following compound when added to cytoplasmic membrane helps in maintaining the rigidity of cell?
d) amino acids
Explanation: Hopanoids are hydrophobic chemical compounds which when added to cytoplasmic membrane forms a stable and hard compound that helps in maintaining the rigidity of cell.
7. The nucleoid can be made visible under the light microscope by _________
a) Methylene blue
c) Nile blue
d) Feulgen staining
Explanation: Bacteria consist of nucleotide, consisting of a single, circular DNA molecule in which all the genes are linked and it is not a discrete nucleus. The nucleoid can be made visible under the light microscope by Feulgen staining,which is specific for DNA.
8. What helps in the heat resistance of endospore?
a) calcium-DPA complex
Explanation: All endospores contain large amounts of dipicolinic acid (DPA). It occurs in combination with large amounts of calcium and is probably located in the central part of the spore.The calcium-DPA complex play a role in the heat resistance of endospores.
9. Cysts also have high heat resistance like endospores.
Explanation: Cysts are dormant, thick-walled, desiccation-resistant forms that develop by differentiation of a vegetative cell and which can later germinate under suitable conditions. In some ways cysts resemble endospores but they do not have the high heat resistance of endospores.
10. Which of the following methods can be utilized for removing peripheral proteins of the cytoplasmic membrane?
a) treatment by detergents
b) osmotic shock
c) heat application
d) destruction of the membrane
Explanation: Peripheral proteins are loosely attached to cytoplasmic membrane and can be removed by mild treatments such as osmotic shock. On the other hand, integral proteins can be removed only by destruction of the membrane, as with treatment by detergents.
11. Which of the following are true for cytoplasmic membrane?
a) hydrophilic barrier
b) hydrophobic barrier
c) site of generation of protonmotive force
d) hydrophobic barrier and site of generation of protonmotive force
Explanation:The cytoplasmic membrane is a hydrophobic barrier to penetration by most water-soluble molecules. Because of its impermeability to protons, the cytoplasmic membrane is the site of generation of the proton motive force.
Sanfoundry Global Education & Learning Series – Microbiology.
To practice all areas of Microbiology, here is complete set of 1000+ Multiple Choice Questions and Answers.