B1.2.8 (HL)—Secondary structure
Secondary structure forms when polypeptide regions coil into alpha helices or fold into beta sheets stabilized by regular hydrogen bonds.
- Syllabus
- First assessment 2025
- Objective
- B1.2.8
- Level
- HL
Exam analysis
Chance of appearing7%of analysed past papers
Latest appearanceMay 2025
Most common paperPaper1
Typical marks1–2
Common command terms
- Describe
- Deduce
- Identify
- Explain
Scoring notes
- Common mistake
- Attributing secondary structure mainly to disulfide bridges or ionic R-group bonds.
Recent exam appearances
May 2025Paper2 ["HL"] · TZ12(c)(i)[ 2 ]B1.2.8 (HL)—Secondary structure
May 2023Paper2 ["HL"] · TZ12(b)[ 1 ]B1.2.8 (HL)—Secondary structure
November 2021Paper2 ["HL"] · TZ04(b)[ 2 ]B1.2.8 (HL)—Secondary structure
May 2018Paper2 ["HL"] · TZ24(a)[ 3 ]B1.2.8 (HL)—Secondary structure
May 2017Paper1 ["HL"] · TZ128[ 1 ]B1.2.8 (HL)—Secondary structure
Practice this objective
Coverage 2012–2025 · Updated 15 Jul 2026
Concept essentials
- Alpha helices and beta pleated sheets are secondary structures.
- Secondary structure is stabilized by hydrogen bonds between backbone C=O and N-H groups.
- Beta sheets may form from parallel or antiparallel polypeptide sections.
- R-group interactions are more characteristic of tertiary structure than secondary structure.