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B1.2.1—Generalized amino acid structure

Amino acids share an alpha-carbon framework with amine, carboxyl, hydrogen and R-group attachments that determine protein chemistry and molecular structure.

Syllabus
First assessment 2025
Objective
B1.2.1
Level
HL

Exam analysis

Chance of appearing4%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1
Typical marks1–3

Common command terms

  • Draw
  • Identify

Scoring notes

Common mistake
Omitting either the amine group or carboxyl group when drawing a generalized amino acid.

Recent exam appearances

November 2025Paper2 ["HL"] · TZ12(b)[ 3 ]B1.2.1—Generalized amino acid structure
May 2022Paper1 ["HL"] · TZ26[ 1 ]B1.2.1—Generalized amino acid structure
May 2021Paper1 ["HL"] · TZ27[ 1 ]B1.2.1—Generalized amino acid structure
May 2014Paper1 ["HL"] · TZ18[ 1 ]B1.2.1—Generalized amino acid structure
Practice this objective

Coverage 2014–2025 · Updated 15 Jul 2026

Concept essentials

  • All amino acids have a central alpha carbon bonded to amine, carboxyl, hydrogen and R-group attachments.
  • The R-group is the variable part that gives amino acids different properties.
  • Proteins contain nitrogen, and some amino acids contain sulfur.
  • Amino acid diagrams must show the functional groups attached to the central carbon.
ConceptIB Biology HL