A1.2.3—Sugar-phosphate bonding
Nucleotides join by condensation reactions to form a continuous sugar-phosphate backbone, leaving bases exposed to carry sequence information along each strand.
- Syllabus
- First assessment 2025
- Objective
- A1.2.3
- Level
- HL
Exam analysis
Chance of appearing2%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper1
Typical marks1
Common command terms
- Identify
- Outline
Scoring notes
- Common mistake
- Mixing up covalent sugar-phosphate bonds with hydrogen bonds between complementary bases.
Recent exam appearances
May 2025Paper2 HL · TZ33(e)(i)[ 1 ]A1.2.3—Sugar-phosphate bonding
November 2012Paper1 HL · TZ07[ 1 ]A1.2.3—Sugar-phosphate bonding
Practice this objective
Coverage 2012–2025 · Updated 14 Jul 2026
Concept essentials
- Sugar-phosphate bonding should be described using precise molecular vocabulary.
- Structure and information must be kept separate: backbones provide continuity while bases carry sequence meaning.
- Exam answers should match the command term and avoid adding unsupported extra claims.