A level Biology B · Edexcel 9BI0 · Topic 2A
Eukaryotic and prokaryotic cells
Key points
- Eukaryotic cells contain a nucleus (with nucleolus and nuclear envelope), mitochondria (aerobic respiration), rough ER (protein synthesis with 80S ribosomes), smooth ER (lipid synthesis), Golgi apparatus (modifies and packages proteins into vesicles) and lysosomes (digestive enzymes).
- Plant cells also have a cellulose cell wall, chloroplasts and a large permanent vacuole.
- Secreted proteins follow the route: rough ER → vesicle → Golgi → secretory vesicle → exocytosis at the membrane.
- Prokaryotic cells are smaller, with circular DNA free in the cytoplasm, plasmids, 70S ribosomes, a peptidoglycan (murein) cell wall, and sometimes a capsule, pili and flagella.
- Prokaryotes have no membrane-bound organelles.
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All living things are made of cells, and cells arise only from existing cells: this is the cell theory. Cells come in two basic designs, and knowing what each structure does lets you explain how specialised cells carry out their roles.
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