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Light Microscopic Features

Largest organelle within the cell with distinct boundary; often visible nucleoli and chromatin pattern regions

Roughly circular, basophilic region within the nucleus; visible in living cells throughout interphase with Interference microscopy

Not visible

Often observed as a basophilic region of cytoplasm referred as "ergastoplasm"

Not visible; cytoplasm in region of sER may exhibit distinct eosinophilia

Sometimes observed as "negative-staining" region; appears as network in heavy-metal-stained preparations; visible in living cells with interference microscopy

Observed only when vesicles are very large (e.g., zymogen granules in pancreas)

Sometimes observed in favorable situations (e.g., liver or nerve cells) as very small, dark dots; visible in living cells stained with vital dyes, e.g., Janus green

Not visible

Visible only after special enzyme histo-chemical staining

Visible only after special enzyme histo-chemical staining

Only observed when organized into large structures (e.g., muscle fibrils)

Not visible

Observed as a "purple haze" region of cytoplasm (metachromasia) with tolul-dine blue-stained specimen

Readily visible when very large (e.g., in adipocytes); appear as large empty holes in section (lipid itself is usually removed by embedding solvents)

Electron Microscopic Features

Surrounded by two membranes (nuclear envelope) containing nuclear pore complexes and perinuclear cisternal space; regions with condensed and diffuse chromatin pattern (hete-rochromatin and euchromatin)

Dense, nonmembranous structure containing fibrillar and granular material

The external membrane and membranes surrounding membranous organelles of the cell; two inner and outer electron-dense layers separated by an intermediate electron-lucent layer

Flattened sheets, sacs, and tubes of membranes with attached ribosomes

Flattened sheets, sacs, and tubes of membranes without attached ribosomes

Stack of flattened membrane sheets, often adjacent to one side of the nucleus

Many relatively small, membrane-bounded vesicles of uniform diameter; often polarized on one side of cell

Two-membrane system: outer membrane and inner membrane arranged in numerous folds (cristae); in steroid-producing cells inner membrane arranged in tubular cristae

Tubolovesicular structures with subdivided lumen containing electron-lucent material or other smaller vesicles

Membrane-bounded vesicles, often electron dense

Membrane-bounded vesicles, often with electron-dense crystalloid inclusions Long, linear staining pattern with width and features characteristic of each filament type

Very small dark dots, often associated with the rER

Nonmembranous, very dense grape-like inclusions

Nonmembranous inclusions; generally appear as a void in the section table 2.4. Organelles and Cytoplasmic Inclusions: Functions and Pathologies

Organelle or

Inclusion

Function

Examples of Associated Pathologies

Nucleus Nucleolus Plasma membrane rER sER

Golgi apparatus

Secretory vesicles Mitochondria

Endosomes Lysosomes

Peroxisomes Cytoskeletal element

Ribosomes Glycogen

Lipid droplets

Storage and use of genome

Synthesis of rRNA and partial assembly of ribosomal subunits

Ion and nutrient transport; recognition of environmental signals; cell-to-cell and cell-to-extracellular matrix adhesions

Binds ribosomes engaged in translating mRNA for proteins destined for secretion or for membrane insertion; also involved in chemical modifications of proteins and membrane lipid synthesis

Similar to the rER but lacks the ribosome-binding function; involved in lipid and steroid metabolism

Chemical modification of proteins: sorting and packaging of molecules for secretion or transport to other organelles

Transport and storage of secreted proteins to plasma membrane

Aerobic energy supply (oxidative phosphorylation, ATP); initiation of apoptosis

Transport of endocytosed material; biogenesis of lysosomes

Digestion of macromolecules

Oxidative digestion, e.g., fatty acids

Various functions including cell motility, intracellular and extracellular transport; maintenance of cellular skeleton

Synthesize protein by translating protein-coding sequence from mRNA

Short-term storage of glucose in the form of branched polymer; found In liver, skeletal muscle, and adipose tissue

Storage of esterified forms of fatty acids as high-energy storage molecules

Inherited genetic diseases; environmentally induced mutations

Cystic fibrosis

Intestinal malabsorption syndromes Lactose intolerance

Pseudoachondroplasia

Calcium phosphate dihydrate crystal deposition disease

Hepatic endoplasmic reticular storage disease l-cell disease

Polycystic kidney disease

Lewy bodies of Parkinson's disease Proinsulin diabetes

Mitochondrial myopathies such as MERRF/ MELAS,8 Kearns-Sayre syndromes, and Laber's hereditary optic atrophy

M-6-P receptor deficiency

Glycogen storage disease type II Tay-Sachs disease Metachromatic leukodystrophy

Zellweger's syndrome

Immotile cilia syndrome, Alzheimer's disease, epidermolysis bullosa

Many antibiotics act selectively on bacterial ribosomes, e.g., tetracyclines, aminoglycosides (gentamicin, streptomycin)

There are several known glycogen storage diseases, including major groups of hepatic-hypoglycemic and muscle-en-ergy pathophysiologies

Lipid storage diseases such as Gaucher's and Niemann-Pick disease, liver cirrhosis

^Myoclonic epilepsy and ragged red fibers syndrome.

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes syndrome.

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