Cell Structures (Edexcel IGCSE Biology (Modular)): Revision Note
Exam code: 4XBI1
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Cell Structures
Cells are surrounded by a cell membrane, which separates them from their external environment
Inside the cell membrane is the cytoplasm, a jelly-like substance of water with dissolved substances
Eukaryotic cells have organelles within the cytoplasm
Organelles are subcellular structures that carry out specific functions within the cell
Within the cytoplasm of eukaryotic cells the following organelles are present:
Nucleus
Ribosomes
Mitochondria
Watch out for the difference between the terms 'mitochondria' and 'mitochondrion'
Mitochondrion is used to refer to one organelle
Mitochondria is used to refer to more than one organelle eg. muscle cells contain many mitochondria
Plant cells contain the following additional structures:
Cell wall
Chloroplasts
Permanent vacuole
When viewed under a microscope the structures inside a plant cell are visible. Some cellular structures, like ribosomes and mitochondria, are too small to be viewed under a light microscope but are visible under an electron microscope.
Cell Structures & Functions
Cellular Structures & Functions Table
Structure | Function |
|---|---|
Nucleus | Contains genetic material (chromosomes) |
Cytoplasm | Site of many chemical reactions Contains water and many solutes |
Cell membrane | Controls substances entering and leaving the cell |
Cell wall | Gives the cell extra support and defines its shape, prevents bursting |
Mitochondria | Site of aerobic respiration |
Chloroplasts | Site of photosynthesis Contains chlorophyll to absorb light for photosynthesis |
Ribosomes | Site of protein synthesis |
Vacuole | Contains cell sap (water with dissolved solutes) |
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