What is the Difference Between Thymine and Thymidine?

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Thymine and thymidine are related molecules found in DNA. The key difference between them is that thymine is a nucleobase, while thymidine is a nucleoside. Here are the main differences between thymine and thymidine:

  • Thymine:
  • One of the four nucleobases in DNA.
  • Chemical formula: C5H6N2O2.
  • Molar mass: 126.15 g/mol.
  • Replaced by uracil in RNA.
  • Forms a base pair with adenine in DNA.
  • Thymidine:
  • A nucleoside composed of thymine and a ribose sugar molecule.
  • Also known as deoxythymidine, deoxyribosylthymine, or thymine deoxyriboside.
  • Chemical formula: C10H14N2O5.
  • Pair with deoxyadenosine (A) in double-stranded DNA.

In summary, thymine is a nucleobase that is one of the building blocks of DNA, while thymidine is a nucleoside composed of thymine and a ribose sugar molecule.

Comparative Table: Thymine vs Thymidine

Here is a table comparing the differences between thymine and thymidine:

Feature Thymine Thymidine
Definition Thymine is a nucleobase, one of the four major nucleobases in DNA. Thymidine is a nucleoside, consisting of thymine and a ribose sugar molecule.
Chemical Formula C5H6N2O2 C5H6N2O2 + (ribose sugar)
Molar Mass 126.15 g/mol (not specified)
Pairing Pairs with adenine in DNA structures. Pairs with adenine in DNA structures via hydrogen bonds.
RNA Equivalent Thymine is absent in RNA, replaced by uracil. Thymidine is replaced by other nucleosides in RNA.
DNA Structure Stabilizes nucleic acid structures in DNA. Part of DNA structure and can be phosphorylated.

Thymine is a nucleobase found only in DNA, while thymidine is a nucleoside consisting of thymine and a ribose sugar molecule. Thymine pairs with adenine in DNA structures, and it is absent in RNA, where it is replaced by uracil. Thymidine can be phosphorylated and is part of the DNA structure.