1. Which among the following is associated with the export of exocellular enzymes?
a) central mesosomes
b) peripheral mesosomes
c) thylakoids
d) nucleus
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 the export of exocellular enzymes such as penicillinase.
2. Ribosomes of prokaryotes have a sedimentation coefficient of?
a) 90S
b) 80S
c) 50S
d) 70S
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.
3. 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.
4. Which among the following compound when added to cytoplasmic membrane helps in maintaining the rigidity of cell?
a) lipopolysaccharide
b) hopanoid
c) phosphoglycerides
d) amino acids
Explanation: Hopanoids are hydrophobic chemical compounds which when added to the cytoplasmic membrane forms a stable and hard compound that helps in maintaining the rigidity of cell.
5. The nucleoid can be made visible under the light microscope by _________
a) Methylene blue
b) Iodine
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.
6. What helps in the heat resistance of the endospore?
a) calcium-DPA complex
b) water
c) methylene
d) calcium
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 plays a role in the heat resistance of endospores.
7. Cysts also have high heat resistance like endospores.
a) True
b) False
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.
8. 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 the destruction of the membrane, as with treatment by detergents.
9. 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 the generation of the proton motive force.
10. The organisms which can use reduced inorganic compounds as electron donors are known as _________
a) chemotrophs
b) organotrophs
c) lithotrophs
d) phototrophs
Explanation: Organisms that can use reduced inorganic compounds as electron donors are termed as lithotrophs. Some organisms which use organic compounds as electron donors are called organotrophs.