TABLE Organelles and Cytoplasmic Inclusions: Functions and Pathologies 2.2 Organelle or Inclusion Function Examples of Associated Pathologies Nucleus Storage and use of genome Inherited genetic diseases; environmentally induced mutations Nucleolus Synthesis of rRNA and partial Werner syndrome (premature aging assembly of ribosomal subunits disease) Involved in regulation of cell cycle Malfunctions of cell cycle leading to cancerogenesis Plasmamembrane Ion and nutrient transport Cystic fbrosis Recognition of environmental signal Intestinal malabsorption syndromes Cell-to-cell and cell-to-extracellular Lactose intolerance matrix adhesions rER Binds ribosomes engaged in translating Pseudoachondroplasia mRNA for proteins destined for secretion Calcium phosphate dihydrate crystal or for membrane insertion deposition disease Also involved in chemical modifcations of proteins and membrane lipid synthesis sER Involved in lipid and steroid metabolism Hepatic endoplasmic reticular storage disease Golgi apparatus Chemical modifcation of proteins I-cell disease Sorting and packaging of molecules Polycystic kidney disease for secretion or transport to other organelles Secretory vesicles Transport and storage of secreted proteins Lewy bodies of Parkinson’s disease to plasma membrane Proinsulin diabetes Mitochondria Aerobic energy supply (oxidative Mitochondrial myopathies such as MERRFa , phosphorylation, ATP) MELASb, Kearns-Sayre syndromes, and Initiation of apoptosis Leber’s hereditary optic atrophy Endosomes Transport of endocytosed material M-6-P receptor defciency Biogenesis of lysosomes Lysosomes Digestion of macromolecules Lysosomal storage diseases (see  Folder 2.1, Clinical Correlation: Lysosomal Storage Diseases) Peroxisomes Oxidative digestion (e.g., fatty acids) Zellweger’s syndrome Cytoskeletal elements Various functions, including cell motility, Immotile cilia syndrome, Alzheimer’s cell adhesions, intracellular and disease, epidermolysis bullosa extracellular transport Maintenance of cellular skeleton Ribosomes Synthesis of protein by translating Ribosomal dysfunction in Alzheimer’s protein-coding sequence from disease; Diamond-Blackfan anemia mRNA Many antibiotics act selectively on bacterial ribosomes: e.g., tetracyclines, aminoglycosides (gentamicin, streptomycin) Glycogen Short-term storage of glucose in Several known glycogen-storage diseases, the form of branched polymer including major groups of hepatic-Found in liver, skeletal muscle, hypoglycemic and muscle-energy and adipose tissue pathophysiologies Lipiddroplets Storage of esterified forms of fatty acids Lipid storage diseases such as Gaucher’s as high-energy storage molecules and Niemann-Pick disease, liver cirrhosis aMyoclonic epilepsy and ragged red fibers syndrome. bMitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes syndrome.
FIGURE 2.2 • Electron micrograph of microvilli on the apical surface of an absorptive cell. This electron micrograph shows the apical portion of absorptive cells with microvilli. Note that at this magnifcation the plasma membrane displays its characteristic appearance, showing two electron-dense lines separated by an electron-lucent intermediate layer. The glycoproteins of the glycocalyx can be seen extending from the tips of the microvilli into the lumen. The relationship between the outer plasma-membrane leafet and the glycocalyx is particularly well demonstrated. Glycoproteins of the glycocalyx include terminal digestive enzymes such as dipeptidases and disaccharidases.