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🔬 Biology  ·  Biomolecules  ·  NEET

In the Watson-Crick B-DNA model, one complete turn of the double helix spans about:

Answer: 3.4 nm, covering ten base pairs.

  • A 0.34 nm, covering one base pair
  • B 2.0 nm, covering five base pairs
  • C 3.4 nm, covering ten base pairs
  • D 34 nm, covering thirty base pairs

Correct answer: C. 3.4 nm, covering ten base pairs

Explanation: In B-DNA the pitch is ~3.4 nm per turn and each turn contains about 10 base pairs (rise ~0.34 nm per pair).

Enzyme Kinetics: Rate vs Substrate Concentration[Substrate]Reaction rateVmaxKm½VmaxCurve flattens at high [S]: ALL enzyme active sites are occupied (saturation)

As substrate concentration rises, reaction rate increases steeply at first, then plateaus at Vmax once every enzyme molecule is working at full capacity; Km is the substrate concentration giving half-maximal rate, and a LOWER Km means the enzyme reaches that rate with less substrate (higher affinity).

Concept context

Carbohydrates, proteins, lipids, nucleic acids, and enzyme kinetics. Essential foundation for understanding metabolism.

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