Eukaryotic and prokaryotic cell structure, the roles of organelles, the protein-secretion pathway, and microscopy and magnification calculations.
Cells are the basic unit of life. Eukaryotic cells (animal, plant, fungal) have a membrane-bound nucleus and organelles; prokaryotic cells (bacteria) are smaller and lack a true nucleus and membrane-bound organelles.
Organelles and their functions
| Organelle | Function | |---|---| | Nucleus | holds DNA; controls the cell; nucleolus makes ribosomes | | Mitochondrion | aerobic respiration → ATP; double membrane, folded cristae | | Ribosome (80S/70S) | site of protein synthesis (translation) | | Rough ER | ribosomes on surface; transports proteins | | Smooth ER | synthesises lipids | | Golgi apparatus | modifies, packages and secretes proteins (in vesicles) | | Lysosome | contains hydrolytic enzymes; digests material | | Centriole | forms spindle fibres in cell division | | Cell wall (plant) | cellulose; support and shape | | Chloroplast (plant) | photosynthesis | | Vacuole (plant) | turgor/support; stores sap |
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