Cell structure and specialised cells — Edexcel GCSE Combined Science
Sub-cellular structures in animal, plant and bacterial cells, and how sperm, egg and ciliated cells are adapted to their jobs.
Revision notes
3 short notes, in the order of the specification. Each one in short:
Animal and plant cells are eukaryotic cells, which means their genetic material is enclosed in a nucleus. Both have a nucleus, cell membrane, mitochondria and ribosomes. Plant cells also have a cellulose cell wall that strengthens the cell, chloroplasts that absorb light for photosynthesis, and a vacuole containing cell sap that helps keep the cell firm.
Bacteria are prokaryotic cells, so they do not have a nucleus. Their chromosomal DNA is a single loop found free in the cytoplasm, and they often have small rings of extra DNA called plasmids. Unlike animal and plant cells, bacteria have no mitochondria, and some have a flagellum that moves to make the bacterium swim.
A specialised cell has adaptations that help it do its job. A sperm cell has an acrosome of digestive enzymes, a haploid nucleus, many mitochondria and a tail to swim to the egg. An egg cell has nutrients in its cytoplasm and a haploid nucleus. Ciliated epithelial cells have cilia that beat to move mucus away from the lungs.
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Quick check questions
Name the three structures found in plant cells but not in animal cells.
Show answer
Cell wall, chloroplasts and vacuole.
Where is the DNA in a bacterial cell?
Show answer
Free in the cytoplasm, as chromosomal DNA and plasmid DNA. There is no nucleus.
What is the function of the acrosome?
Show answer
It contains enzymes that digest the outer layers of the egg.
Why does a sperm cell have a haploid nucleus?
Show answer
It has half the chromosomes, so fusing with the egg nucleus gives the full number.
What do the cilia on ciliated epithelial cells do?
Show answer
They move mucus containing trapped dust and microorganisms away from the lungs.
Frequently asked questions
What is the difference between prokaryotic and eukaryotic cells?
Eukaryotic cells, such as animal and plant cells, have their genetic material enclosed in a nucleus, while prokaryotic cells, such as bacteria, do not. In bacteria the chromosomal DNA is a single loop free in the cytoplasm, often with plasmids. Prokaryotic cells also have no mitochondria, and some have flagella.
Why do plant cells have a cell wall?
Plant cells have a cell wall because it strengthens the cell and supports it. The cell wall is made of cellulose and surrounds the cell membrane. Animal cells do not have a cell wall. Plant cells also have chloroplasts for photosynthesis and a vacuole of cell sap that helps keep the cell firm.
How is a sperm cell adapted to its function?
A sperm cell is adapted to reach an egg cell and fuse with it. Its tail moves from side to side so it can swim, and many mitochondria release energy by aerobic respiration for the tail. The acrosome contains digestive enzymes to break into the egg, and the haploid nucleus has half the chromosomes.
What do mitochondria do in a cell?
Mitochondria are where aerobic respiration takes place, releasing energy for the cell. They are found in animal and plant cells but not in bacteria. In exams, write that mitochondria release energy, never that they 'make energy'. Cells that need a lot of energy, such as sperm cells, have many mitochondria.
Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026