MCAT Organic Chemistry Question 149: Answer and Explanation

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Question: 149

14. When a bond is created between two nucleotide triphosphates in DNA synthesis, the small molecule released from this reaction is:

  • A. pyrophosphate.
  • B. inorganic phosphate.
  • C. ATP.
  • D. organic phosphate.

Correct Answer: A

Explanation:

As DNA is synthesized, it forms phosphodiester bonds, releasing pyrophosphate, PPi. Pyrophosphate is an inorganic phosphate-containing molecule, but it is not the single phosphate group commonly referred to as inorganic phosphate, choice (B). The DNA molecule itself is referred to as an organic phosphate, choice (D).

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