Botany · Ch 6 — Cell: The Unit of Life
Cell Organelles
Cell Organelles
With the outer boundary and general contents of the cell established, the chapter now turns to the individual working parts inside it - the cell organelles. This is the longest and most detailed section of the chapter, moving systematically through the endomembrane system as a unifying concept, then the endoplasmic reticulum, Golgi body, mitochondria, the plastid family (including the chloroplast), ribosomes, lysosomes, and the smaller single-membrane organelles (peroxisomes, glyoxysomes, and the broader category of microbodies), sphaerosomes, the non-membranous centri …
Cell Inclusions
Cell inclusions are simply the non-living materials found suspended within a cell's cytoplasm - as opposed to the living organelles covered in the rest of this section, inclusions are metabolic products, storage reserves, or waste, made up of a mix of organic and inorganic compounds. In prokaryotes, common reserve-material inclusions include phosphate granules, cyanophycean granules, glycogen granules, poly-beta-hydroxy-butyrate granules, sulphur granules, carboxysomes, and gas vacuoles; among these, the inorganic inclusions specific to bacteria are polyphosphate granules (also called volutin granules) and sulphur granules, and both of these are additionally known collectively as metachromatic granules. In eukaryotes, cell inclusions fall into several recognisable categories. Reserve food materials include starch grains, glycogen granules, aleurone grains and fat droplets. Plant cell secretions include essential oils, resins, gums, latex and tannins. Inorganic crystals found in plant cells are built of calcium carbonate, calcium oxalate or silica, and several of these have their own specific names and plant examples: a cystolith is a calcium carbonate deposit found in the hypodermal leaf cells of Ficus bengalensis; sphaeraphides are star-shap …