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IB Biology
A Unity and Diversity
A1.1 Water
A1.2 Nucleic acids
A2.1 Origins of cells
A2.2 Cell structure
A3.1 Diversity of organisms
A4.1 Evolution and speciation
A4.2 Conservation of biodiversity
B Form and Function
B1.1 Carbohydrates and lipids
B1.2 Proteins
B2.1 Membranes and membrane transport
B2.2 Organelles and compartmentalisation
B2.3 Cell specialisation
B3.1 Gas exchange
B3.2 Transport
B4.1 Adaptation to environment

A2.2 Cell structure

Cell structure connects microscopy, universal cellular organization, prokaryotic and eukaryotic diversity, specialized exceptions, differentiation, and evolutionary explanations for complex cells and multicellularity.

Syllabus
First assessment 2025
Topic
A2.2
Level
SL

Exam analysis

Chance of appearing61%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1
Typical marks1

Most tested objectives

  1. A2.2.5—Prokaryote cell structure35 past papers35 questions
  2. A2.2.2—Microscopy skills23 past papers27 questions
  3. A2.2.12 (HL)—Endosymbiosis origin of eukaryotes20 questions

Common question formats

  • Definition or recall
  • Graph interpretation
  • Process explanation
  • Calculation
  • Evaluation
  • Structured response

Recent exam appearances

November 2025Paper2 ["SL"] · TZ13(d)[ 1 ]A2.2.9—Atypical cell structure
November 2025Paper2 ["SL"] · TZ13(c)[ 1 ]A2.2.8—Differences in eukaryotic cells
November 2025Paper2 ["SL"] · TZ13(b)[ 1 ]A2.2.6—Eukaryote cell structure
November 2025Paper1B ["SL"] · TZ31(c)[ 2 ]A2.2.4—Structures common to all cells
November 2025Paper1B ["SL"] · TZ31(b)(ii)[ 1 ]A2.2.2—Microscopy skills
Practice this topic

Coverage 2010–2025 · Updated 15 Jul 2026

Objective notes

11 learning objectives
A2.2.1Cells as basic structural unit

• Cells are the basic structural and functional units of living organisms

• Cells carry out essential life processes and are usually microscopic

7 questions · 7 past papers · low frequency

A2.2.2Microscopy skills

• Use light microscopes to prepare mounts, stain specimens, and observe cells

• Measure cells with eyepiece graticules and stage micrometers

• Calculate magnification, actual size, and scale bars

27 questions · 23 past papers · low frequency

A2.2.3Developments in microscopy

• Resolution, not only magnification, determines visible detail

• TEM reveals internal ultrastructure; SEM reveals surface detail

• Cryogenic EM, fluorescence, and immunofluorescence reveal molecules and specific structures

1 question · 1 past paper · low frequency

A2.2.4Structures common to all cells

• All cells have a plasma membrane, cytoplasm, DNA, and ribosomes

• These structures control exchange, support metabolism, store information, and make proteins

3 questions · 3 past papers · low frequency

A2.2.5Prokaryote cell structure

• Prokaryotes lack a nucleus and membrane-bound organelles

• Structure includes cell wall, plasma membrane, cytoplasm, 70S ribosomes, naked circular DNA, and plasmids

• E. coli, Bacillus, and Staphylococcus are bacterial examples

35 questions · 35 past papers · medium frequency

A2.2.6Eukaryote cell structure

• Eukaryotes have a nucleus, 80S ribosomes, cytoskeleton, and compartmentalized cytoplasm

• Organelles include mitochondria, ER, Golgi apparatus, vesicles, lysosomes, and vacuoles

• Plant cells may include chloroplasts, large vacuoles, and cellulose cell walls

10 questions · 7 past papers · low frequency

A2.2.7Processes of life in unicellular organisms

• Unicellular organisms carry out all life processes in one cell

• Examples include Amoeba, Chlamydomonas, and Escherichia coli

• Processes include nutrition, metabolism, response, excretion, homeostasis, growth, and reproduction

6 questions · 6 past papers · low frequency

A2.2.8Differences in eukaryotic cells

• Animal, fungal, and plant cells differ in cell walls, vacuoles, and storage structures

• Plant cells have cellulose walls, chloroplasts, and large permanent vacuoles

• Animal cells may have centrioles, cilia, flagella, lysosomes, and temporary vacuoles

6 questions · 6 past papers · low frequency

A2.2.9Atypical cell structure

• Atypical cells show limits of simple cell theory

• Examples include multinucleate fungal hyphae and striated muscle fibres

• Red blood cells and phloem sieve tubes lack nuclei at maturity

5 questions · 5 past papers · low frequency

A2.2.10Cell identification in micrographs

• Identify prokaryotic, plant, and animal cells in light and electron micrographs

• Recognize organelles such as nucleus, mitochondria, chloroplasts, ER, Golgi, vacuoles, and ribosomes

• Use visible structures, scale, and tissue context as evidence

9 questions · 8 past papers · low frequency

A2.2.11Drawing and annotation

• Draw clear biological diagrams from electron micrographs without shading

• Label visible organelles and include magnification or scale information

• Annotate structures with functions where required

1 question · 1 past paper · low frequency