AQA Biology GCSE - Topic 1: Cell Biology - Cell structure and specialisation notes

Sep 5, 2026

Comprehensive AQA Biology GCSE notes for Topic 1: Cell Biology, covering the core differences between prokaryotic and eukaryotic cells, with detailed functions of key organelles such as nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, and plant-only structures including chloroplasts, permanent vacuole, and cell wall. Includes guidance on using powers of ten/prefixes for sub-cellular size calculations, plus how cells differentiate and examples of specialised animal and plant cells such as sperm, nerve, muscle, root hair, and xylem cells.

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Topic 1: Cell Biology

Cell Structure (1.1)

Cell Specialisation (1.1.3)

Examples of specialised cells in animals

Examples of specialised cells in plants

AQA Biology GCSE # Topic 1: Cell Biology NotesContent in bold is for higher tier only. Content is for both separate science and double award students unlessindicated in heading. ## Cell Structure (1.1) Eukaryotes and Prokaryotes (1.1.1) All living things are made of cells, which can either be prokaryotic or eukaryotic. Animal and plant cells are eukaryotic. They have a: ● Cell membrane ● Cytoplasm ● Nucleus containing DNA Bacterial cells are prokaryotic and are much smaller. They have a: ● Cell wall ● Cell membrane ● Cytoplasm ● Single circular strand of DNA and plasmids (small rings of DNA found in thecytoplasm) The structures mentioned above (e.g. cell membrane) are examples of organelles -structures in a cell that have different functions Cells are extremely small, and we can use orders of magnitude to understand how muchbigger or smaller one is from another: If an object is 10 times bigger than another then we say itis 101 times bigger. If an object is 1000 times bigger than another then we say itis 103 times bigger. If an object is 10 times smaller than another then we say itis 10-1 times smaller. Prefixes go before units of measurement (such as ‘metres’) to show the multiple of theunit. | Prefix | Multiply unit by. . . | | --- | --- | | Centi | 0.01 | | Milli | 0.001 | | Micro | 0.000, 001 | | Nano | 0.000, 000, 001 | Animals and Plants (1.1.2) The subcellular structures inside cells all have a specific function.In animal and plant cells. . . | Structure | Function | | --- | --- | | Nucleus | ● Contains DNA coding for a particular
● protein needed to build new cells.
Enclosed in a nuclear membrane. | | Cytoplasm | ● Liquid substance in which chemical
● reactions occur.
Contains enzymes (biological
catalysts, i.e. proteins that speed up
● the rate of reaction) .
Organelles are found in it | | Cell membrane | ● Controls what enters and leaves the
cell | | Mitochondria | ● Where aerobic respiration reactionsoccur, providing energy forthe cell | | Ribosomes | ●● Where protein synthesis occurs.
Found on a structure called the roughendoplasmic reticulum. | Only in plant cells … | Structure | Function | | --- | --- | | Chloroplasts | ● Where photosynthesis takes place,
● providing food forthe plant
Contains chlorophyll pigment (whichmakes it green) which harvests thelight needed for photosynthesis. | | Permanent vacuole | ●● Contains cell sap
● Found within the cytoplasm
Improves cell’s rigidity | | Cell wall (also present in algal cells) | ●● Made from cellulose
Provides strength to the cell | Bacterial cells are prokaryotic, so do not share as many similarities in the typeoforganelles as animal and plant cells do. In bacterial cells. . . | Structure | Function | | | --- | --- | --- | | Cytoplasm | | Above | | Cell membrane | | Above | | Cell wall | | Made of a different compound(peptidogylcan) | | Single circular strand of DNA | | As they have no nucleus, this floats in thecytoplasm | | Plasmids | | Small rings of DNA | To be able to calculate the size or area of sub-cellular structures, you should find a shapesuch as a circle or rectangle that resembles it. The rules that would normally be used tocalculate the size/area of that shape (e.g length x width for a rectangle) should be appliedto it. ## Cell Specialisation (1.1.3) Cells specialise by undergoing differentiation: a process that involves the cell gaining newsub-cellular structures in order for it to be suited to its role. Cells can either differentiateonce early on or have the ability to differentiate their whole life (these are called stemcells) . In animals, most cells only differentiate once, but in plants many cells retain theability. ## Examples of specialised cells in animals ### 1. Sperm cells: specialised to carry the male’s DNA to the eg

FAQs

What are the main differences between prokaryotic and eukaryotic cells?

Prokaryotic cells are much smaller and do not have a nucleus, while eukaryotic cells contain a nucleus holding DNA. Animal and plant cells are eukaryotic and share organelles such as nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes, whereas bacterial cells have cell wall differences and circular DNA plus plasmids.

What roles do the nucleus, cytoplasm, and cell membrane play?

The nucleus contains DNA and is enclosed by a nuclear membrane. Cytoplasm is where chemical reactions occur and contains enzymes, with organelles found within it. The cell membrane controls what enters and leaves the cell.

How does cell differentiation relate to specialised cells?

Cells specialise by undergoing differentiation, gaining new sub-cellular structures to suit their role. Differentiation may happen once early on or throughout life in stem cells, and specialised structures enable each cell type’s function.

Sep 5, 2026

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