Cell Biology and Cytology
Core concepts
A candidate must know the cell theory, the prokaryote/eukaryote divide, and the structure–function pairing of every organelle: nucleus (chromatin, nucleolus, nuclear envelope with pores), rough and smooth ER, Golgi apparatus, mitochondria, plastids, lysosomes, peroxisomes, ribosomes, cytoskeleton (microfilaments, intermediate filaments, microtubules), and the cell-surface and cell-wall structures. Know the fluid-mosaic membrane model and the transport categories: simple diffusion, facilitated diffusion, osmosis, primary and secondary active transport, endocytosis and exocytosis. Compare plant and animal cells: cellulose wall, large central vacuole, and plastids versus centrioles and lysosomes. Know the phases of mitosis and meiosis at the level of chromosome behaviour.
Traps
Questions love the exceptions. Ribosomes are not membrane-bound; the Golgi is the sorting hub, not the site of lipid synthesis; the nucleolus makes rRNA, not ribosomes for export. Prokaryotes lack a nuclear envelope but do have ribosomes. Osmosis is water movement across a semipermeable membrane down its own potential, not solute movement. Distinguish the cell plate (plants) from the cleavage furrow (animals) in cytokinesis. Do not confuse chromatin with chromosomes: same material, different condensation state.
Worked example / rule of thumb
Rule of thumb: "membrane-bound means eukaryotic compartment; no membrane means ribosome, nucleoid, or inclusion." Worked example: a cell with a cellulose wall, a large vacuole, chloroplasts, and no centrioles is a plant cell; a cell with centrioles, lysosomes, and no wall is an animal cell. If a question asks where a secreted protein is finished and sorted, the answer is the Golgi apparatus after rough ER.