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A2.2.9—Atypical cell structure

Multinucleate fibres, anucleate transport cells, and other atypical cells reveal that cellular organization has important exceptions without removing the broader value of cell theory.

Syllabus
First assessment 2025
Objective
A2.2.9
Level
SL

Exam analysis

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

Common command terms

  • Identify
  • Discuss
  • State

Scoring notes

Common mistake
Treating an atypical cell as evidence that the entire cell theory is false.

Recent exam appearances

November 2025Paper2 ["SL"] · TZ13(d)[ 1 ]A2.2.9—Atypical cell structure
May 2024Paper1 ["SL"] · TZ21[ 1 ]A2.2.9—Atypical cell structure
November 2018Paper2 ["SL"] · TZ05(c)[ 7 ]A2.2.9—Atypical cell structure
May 2018Paper1 ["SL"] · TZ11[ 1 ]A2.2.9—Atypical cell structure
May 2017Paper1 ["SL"] · TZ21[ 1 ]A2.2.9—Atypical cell structure
Practice this objective

Coverage 2017–2025 · Updated 15 Jul 2026

Atypical Cell Structures Need a Careful Definition

Atypical eukaryotic cells show that one cell does not always contain exactly one nucleus.

Example Nuclear arrangement Functional consequence
Aseptate fungal hypha Many nuclei share continuous cytoplasm Cytoplasm and materials move along the hypha
Skeletal muscle fibre Multinucleate after cell fusion Supports a very large contractile cell
Mammalian red blood cell Loses nucleus at maturity More space for haemoglobin but no division
Phloem sieve tube element Loses nucleus at maturity More open transport pathway; depends on companion cells

A skeletal muscle fibre is one long multinucleate cell, whereas an aseptate fungal hypha contains many nuclei in a cytoplasm not divided by complete cross-walls.

Atypical does not mean non-cellular. Identify the continuous membrane boundary and explain the altered nuclear arrangement.

Atypical cell structure

Assessment in practice

1 marks
How it is assessed

This objective is assessed through essay response, commonly using Identify / Discuss / State.

Command terms

Identify / Discuss / State

What earns marks

Build the answer around this relationship: Striated muscle fibres contain many nuclei in a shared cytoplasm.

Watch for

Treating an atypical cell as evidence that the entire cell theory is false.

Representative question

Question 1

[Maximum number: 7]

Discuss the cell theory and its limitations.

SL Retrieval: Read, Identify, Draw

The SL core is a practical chain. First, understand cells as structural and functional units. Then use microscopes correctly: prepare, stain, calibrate, measure, and choose a method based on resolution and the detail needed. Finally, identify cell types from visible evidence and draw only what the micrograph shows. This is how the topic turns from definitions into exam performance.

  • Cell theory: cells are structural and functional units.
  • Microscopy: resolution, calibration, magnification, actual size, and scale bars.
  • Cell identity: universal parts, prokaryote/eukaryote differences, and plant/animal/fungal evidence.
  • Micrograph work: justify from visible structures, scale, and context.
  • Drawing: clear lines, no shading, visible labels only, scale/magnification included.

Concept essentials

  • Striated muscle fibres contain many nuclei in a shared cytoplasm.
  • Aseptate fungal hyphae can extend without complete cellular cross-walls.
  • Mature mammalian red blood cells lack nuclei.
  • Atypical cells qualify simplified cell models while retaining a cellular origin.