Which component of an enzyme binds to the substrate?
Allosteric site
Active site
Induced fit site
Substrate attachment site
The Correct Answer is B
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.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. Guanine: Guanine pairs with cytosine in both DNA and RNA through three hydrogen bonds. It does not pair with uracil, as the chemical structure of uracil does not allow stable hydrogen bonding with guanine.
B. Adenine: In RNA, uracil replaces thymine and forms two hydrogen bonds with adenine. This base-pairing maintains the complementary structure needed for RNA transcription and folding, ensuring accurate coding during protein synthesis.
C. Thymine: Thymine is found only in DNA and pairs with adenine. In RNA, uracil substitutes for thymine, so thymine does not pair with uracil.
D. Cytosine: Cytosine pairs with guanine via three hydrogen bonds in both DNA and RNA. Cytosine does not pair with uracil because the hydrogen bonding does not match the structural requirements.
Correct Answer is A
Explanation
A. Thick peptidoglycan layer: Gram-positive bacteria have a thick, multilayered peptidoglycan cell wall that retains the crystal violet-iodine complex during the Gram staining process. This dense layer prevents the dye from being washed out during the alcohol decolorization step, causing Gram-positive bacteria to appear purple under a microscope.
B. Outer membrane: The outer membrane is characteristic of Gram-negative bacteria, not Gram-positive bacteria. It contains lipopolysaccharides and provides an additional barrier but does not contribute to the retention of crystal violet in Gram-positive organisms.
C. Lipopolysaccharide: Lipopolysaccharides (LPS) are components of the outer membrane of Gram-negative bacteria and play a role in pathogenicity and immune activation. LPS is absent in Gram-positive bacteria and therefore does not influence their purple coloration during Gram staining.
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