Bacillus spores survive extreme heat and drying because they are:
Resistant survival structures
Reproductive cells
Energy-producing cells
The Correct Answer is A
A. Resistant survival structures: Bacillus spores, also called endospores, are highly durable, dormant structures formed in response to harsh environmental conditions. They have a thick protective coat, dehydrated core, and DNA-stabilizing proteins, which allow them to survive extreme heat, desiccation, radiation, and chemical disinfectants. Their primary function is survival, not growth or reproduction.
B. Reproductive cells: Spores in Bacillus are not reproductive; they do not produce new bacteria directly. Reproduction in bacteria typically occurs through binary fission. Endospores are a survival mechanism to endure unfavorable conditions and germinate into vegetative cells when the environment becomes favorable.
C. Energy-producing cells: Spores are metabolically inactive and do not produce energy. Their dormant state minimizes metabolic activity, conserving energy and resources until conditions allow the spore to germinate and resume normal cellular functions.
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Related Questions
Correct Answer is A
Explanation
A. Pilus: During bacterial conjugation, a specialized structure called a sex pilus (or conjugation pilus) forms a direct connection between two bacterial cells. The donor cell transfers a copy of plasmid DNA or other genetic material through this pilus to the recipient cell, allowing for horizontal gene transfer and the spread of traits such as antibiotic resistance.
B. Capsule: The bacterial capsule is a polysaccharide layer that surrounds the cell wall and provides protection against phagocytosis and desiccation. It does not play a role in the transfer of DNA between bacterial cells, and therefore is not involved in conjugation.
C. Flagellum: The flagellum is a whip-like appendage that enables bacterial motility. While important for movement and chemotaxis, it is not used for DNA transfer during conjugation. DNA exchange occurs specifically through the pilus, not through flagella.
Correct Answer is B
Explanation
A. Allosteric inhibition: Allosteric inhibition occurs when a molecule binds to a site other than the enzyme’s active site (the allosteric site), causing a conformational change that reduces enzyme activity. It does not involve direct competition between similar substrates for the active site.
B. Competitive inhibition: Competitive inhibition occurs when two molecules that are similar in shape and size compete for binding at the enzyme’s active site. One molecule (the inhibitor) can occupy the active site, preventing the other substrate from binding. This type of inhibition can often be overcome by increasing the concentration of the actual substrate.
C. Active inhibition: “Active inhibition” is not a standard term in enzymology. It does not specifically describe the process in which molecules compete for the same active site and therefore does not accurately represent the scenario described.
D. Noncompetitive inhibition: Noncompetitive inhibition occurs when an inhibitor binds to a site other than the active site, changing the enzyme’s shape and reducing its activity regardless of substrate concentration. Unlike competitive inhibition, the inhibitor does not compete with the substrate for the active site.
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