Animal, fungal and plant cells, and atypical cells

Cells (Unity and diversity) · Cell structure · note 6 of 7

Spec A2.2.8, A2.2.9Download all Cell structure notes (PDF)Download all notes (PDF)12 pages

Animal, fungal and plant cells, and atypical cellsSpec A2.2.8, A2.2.9

In short

Plant, fungal and animal cells differ in their cell walls, vacuoles, plastids, centrioles, cilia and flagella. Plants have cellulose walls, large permanent vacuoles and chloroplasts; fungi have chitin walls and no plastids; animals have no wall but have centrioles. Atypical cells include multinucleate aseptate fungal hyphae and skeletal muscle fibres, and red blood cells and sieve tubes without nuclei.

Differences in eukaryotic cell structure
Feature	Animal cells	Fungal cells	Plant cells
Cell wall	Absent	Present, made of chitin	Present, made of cellulose
Vacuoles	Small and temporary, such as food vacuoles and vesicles	Present; can be large in older hyphae	A large permanent central vacuole of cell sap; maintains turgor and stores substances
Chloroplasts and other plastids	Absent	Absent	Chloroplasts in green tissues; other plastids, such as amyloplasts, store starch
Centrioles	Present	Absent in most fungi	Absent in flowering plants
Cilia and flagella	Present in some cells, such as ciliated epithelium and the sperm flagellum	Absent in most fungi; only some produce spores with flagella	Absent in flowering plants; mosses and ferns have sperm with flagella

Common mistake:

Not every plant cell has chloroplasts: root cells have none. Write 'plant cells may have chloroplasts' when comparing cell types.

Atypical cell structure in eukaryotes

Cell theory pictures a cell as one unit with one nucleus. The numbers of nuclei show that some eukaryotic cells are atypical.

Atypical cells
Cell	Number of nuclei	Explanation
Aseptate fungal hyphae	Many	The long hyphae have no cross walls (septa), so many nuclei share one continuous cytoplasm
Skeletal muscle fibres	Many	Each fibre forms when many embryonic muscle cells fuse, and it can be several centimetres long
Red blood cells (mammals)	None	The nucleus is lost as the cell matures, leaving more space for haemoglobin; the cell cannot divide and lives about 120 days
Phloem sieve tube elements	None	The nucleus and most organelles break down so sap can flow freely; a companion cell with a nucleus keeps each element alive

Four atypical eukaryotic cells: an aseptate fungal hypha with no septa and many nuclei; a striated skeletal muscle fibre with many nuclei at the edge, formed by fusion of cells; a mammalian red blood cell, a biconcave disc with no nucleus; and a phloem sieve tube element with sieve plates and no nucleus beside a companion cell that has a nucleus. — Atypical cells: two with many nuclei and two with none

Written and checked against the IB Biology SL specification · Updated October 2026

Frequently asked questions

What is the difference between prokaryotic and eukaryotic cells?

Prokaryotic cells have no nucleus: their DNA is a naked loop in the cytoplasm, and they have 70S ribosomes and no membrane-bound organelles. Eukaryotic cells have a nucleus with a double membrane and pores, chromosomes of DNA bound to histones, 80S ribosomes, membrane-bound organelles and a cytoskeleton.

How do you calculate magnification in biology?

Magnification equals the size of the image divided by the actual size of the specimen. Measure the image with a ruler, convert both values to the same unit, usually micrometres (1 mm = 1000 µm), then divide. Rearranged, actual size equals image size divided by magnification, which is how cell sizes are found from micrographs.

How do you calculate magnification using a scale bar?

Measure the length of the scale bar on the image with a ruler, convert it to the same unit as the value written on the bar, then divide the measured length by that value. For example, a 20 mm bar labelled 0.5 µm gives 20 000 µm divided by 0.5 µm, a magnification of ×40 000.

All 4 questions on Cell structure