Spirochetes move in a corkscrew pattern through
Periplasmic flagella
Pili
Capsules
The Correct Answer is A
A. Periplasmic flagella: Spirochetes have flagella located within the periplasmic space between the inner and outer membranes. These internal flagella, also called axial filaments, rotate to produce a corkscrew-like motion, allowing the bacterium to move efficiently through viscous environments such as mucus or connective tissue. This unique mechanism is characteristic of genera like Treponema and Borrelia.
B. Pili: Pili are hair-like appendages on the surface of many bacteria used primarily for attachment to surfaces and for conjugation (gene transfer). Pili do not contribute to the corkscrew motility seen in spirochetes.
C. Capsules: Capsules are extracellular polysaccharide layers that protect bacteria from phagocytosis and desiccation. While important for virulence and immune evasion, capsules do not play a role in bacterial motility or the corkscrew movement of spirochetes.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. Allosteric site: The allosteric site is a region on the enzyme separate from the active site where regulatory molecules can bind. Binding at this site can change the enzyme’s conformation and alter its activity, either enhancing or inhibiting substrate binding, but the allosteric site does not directly interact with the substrate.
B. Active site: The active site is the specific region of the enzyme where the substrate binds. Its three-dimensional shape and chemical properties complement the substrate, allowing precise interaction. Binding at the active site facilitates the conversion of substrate to product, often stabilizing the transition state and lowering the activation energy of the reaction.
C. Induced fit site: The term “induced fit” describes the conformational change that occurs in the enzyme when the substrate binds to the active site, allowing tighter binding and optimal positioning for catalysis. It is not a separate site; rather, it refers to the dynamic adjustment of the active site itself.
D. Substrate attachment site: This is a general descriptive term and not a standard term in enzymology. The actual site where substrate molecules specifically bind is the active site, which is structurally and chemically tailored to the substrate.
Correct Answer is D
Explanation
A. winds and zips RNA: Helicase does not function on RNA by winding or zipping. RNA processing involves other enzymes such as RNA polymerase, ligases, and splicing machinery, not helicase.
B. unwinds and unzips RNA: Helicase primarily acts on DNA rather than RNA. While some RNA helicases exist, in the context of DNA replication, helicase unwinds DNA strands, not RNA.
C. supercoils DNA: DNA supercoiling is managed by topoisomerases, such as DNA gyrase, not helicase. Supercoiling relieves torsional stress during replication and transcription.
D. unwinds and unzips DNA: Helicase is an essential enzyme in DNA replication that unwinds the double-stranded DNA helix and separates the two strands by breaking hydrogen bonds between base pairs. This creates replication forks, allowing DNA polymerase to synthesize complementary strands. Its activity is critical for initiating and maintaining the replication process.
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