A Level Biology Practice Exam

What type of bond do phosphodiester bonds form between?

1. Phosphate groups and amino acids

2. Nucleotides and hydroxyl groups

3. Nucleotides and phosphate groups

4. Amino acids and hydroxyl groups

The correct answer is: Nucleotides and phosphate groups

Phosphodiester bonds are significant in forming the backbone of nucleic acids like DNA and RNA. They are specific covalent bonds that link the sugar of one nucleotide to the phosphate group of another nucleotide. This connection occurs through a reaction involving the hydroxyl group on the 3' carbon of one sugar molecule and the phosphate group attached to the 5' carbon of another nucleotide's sugar. Therefore, the correct answer highlights that these bonds specifically join nucleotides together via their phosphate groups, creating a strong and stable structure that supports the overall integrity of the nucleic acid. This arrangement is crucial for facilitating various biological functions, including genetic information storage and transfer.