VAna 104

• Telophase II involves the formation of the nuclear membrane and cytokinesis.
• Belt desmosomes or zonula adherens surround epithelial cell in belt-like fashion, with the two plasma membranes separated by a space 20 nm wide filled with filamentous intracellular material.
• The nuclear matrix is a fibrillar “nucleoskeletal” structure that appears to bind certain hormone receptors and newly synthesized DNA.
• Gap junction is classified as communicating junction where the intercellular spaces are narrowed to approximately 2 nm, bridged by connexons formed by six integral membrane proteins of the apposed membranes, allowing the passage of ions and small molecules from cell to cell, thus permitting the conduction of electrical impulses and possibly functional synchronization and metabolic cooperation of cell.
• Cilia are relatively short hair-like appendages capable of a vibratory beating or lashing movement, commonly found in respiratory system where they function in the movement of mucous film, and are also found in the male and female reproductive systems, where they promote the propulsion of spermatozoa and oocytes.
• Hemidesmosomes consist only one half of the desmosomes and are means for attaching epithelial cells to the basal lamina.
• Nucleoplasm is the matrix in which the other intranuclear components are embedded and is composed of enzymatic and non-enzymatic proteins, metabolites, ions and water.
• Spot desmosomes or macula adherens is a disc-like structure approximately 200-400 nm in diameter, characterized by an intercellular space that is about 20 nm wide and contain electron-dense fine filamentous material that often form an intermediate dense line.
• Newly synthesized rRNA appears third in the region of pars granulosa.
• Microvilli are found in cells whose principal function is absorption, for example, in the cells of the small intestine.
• Flagella are thin, filamentous appendages of cells responsible for swimming motility, with a single long cilium referred to as flagellum.
• Pars granulosa contain dense granules, 15-20 nm in diameter, which represent maturing ribosomal subunits during assembly for export to the cytoplasm.
• Tight junction or zonula occludens is the only impermeable junction in the mammalian organisms and seals neighboring cells together in a belt-like fashion, constraining the passage of substances from the lumen to the intercellular spaces and thus to the internal environment of the organism.
• In many cells, mitochondria are distributed randomly throughout the cytoplasm, but they accumulate in cell types and intracellular regions with higher energy requirements such as cardiac muscle cells, epithelial cells lining the convoluted tubules of the kidney where active transport of ions and water occurs.
• Mitochondria are the site of Kreb’s cycle, providing energy for chemical and mechanical work by storing energy generated from cellular metabolites in the high-energy bonds of ATP.
• Ribosomes are protein-synthesizing organelles, with two basic types: mitochondrial (like prokaryotic) ribosomes are smaller (20 nm) than the cytoplasmic ribosomes of eukaryotes (25 nm), composed of two subunits, and located in the cytoplasm.
• The matrix contains numerous enzymes involved in specialized mitochondrial functions such as the Krebs cycle, transport along the respiratory chain, produce acetyl CoA, β-oxidation of lipids and mitochondrial synthesis.
• The mitochondrial matrix contains water, solutes and large matrix granules believed to be concerned with mitochondrial calcium ion concentration, circular DNA and mitochondrial ribosomes similar to those of bacteria.
• Free polysomes synthesize structural proteins and enzymes for intracellular use, while polysomes of the rough endoplasmic reticulum synthesize proteins to be secreted or sequestered.
• Mitochondria synthesize their own DNA and RNA, possessing some genetic and protein-synthetic potential for the purpose of reproducing themselves.
• The ATP leaves the mitochondrion and releases its stored energy at a variety of intracellular sites.
• Cytoplasmic ribosomes occur in two forms: free ribosomes are individual ribosomes dispersed in the cytoplasm, and polyribosomes (Polysomes) are groups of ribosomes distributed along a single strand of mRNA, an arrangement that permits synthesis of multiple copies of protein from the same message.
• Ribosomes read (translate) the mRNA code and thus play a critical role in assembling amino acids into specific proteins.
• Mitochondria grow and reproduce by fission or budding and can undergo rapid movement and shape changes.
• The endoplasmic reticulum (ER) is a complex organelle involved in the synthesis, packaging and processing of various cell substances, a network of tubular and vesicular structures in the cytoplasm.
• The mitochondrial membranes create two membrane-limited spaces: the intermembrane space, located between the inner and outer membranes and continuous with the intracristal space, and the intercristal space or matrix space, enclosed by the inner membrane and containing the mitochondrial matrix.
• Mitochondria contain enzymes for oxidative phosphorylation and fatty acid oxidation.
• Euchromatins are uncoiled chromatin that stain poorly and are difficult to distinguish even with EM.
• In females, only one X chromosomes either of the two is used by each cell; the inactive X chromosome is often visible as clump of heterochromatin termed sex chromatin, or the Barr body.
• The beaded strand coils into a superhelix with 6 nucleosomes per turn to form the condensed form of chromatin, the heterochromatin.
• Preparing such a picture is called karyotyping that allows cataloging of chromosomes for detection of structural abnormalities and deleted or excess chromosomes.
• The distribution of nuclear chromatin is used to identify cell types, especially in cells with no characteristic cytoplasmic staining properties.
• Nuclear sap or karyolymph is the matrix of the nucleus and the soluble phase of nuclear material.
• A cell’s karyotype is its inventory or a picture of its chromosomes arranged by chromosome type.
• Chromosomes, the most highly condensed form of chromatin, are visible during mitosis.
• The envelope of a cell is perforated by many nuclear pores, each with a diameter of about 70 nm and bounded by eight globular subunits called annular proteins.
• In most euchromatic nuclei, a rim of heterochromatin is often found in the inner surface of the nuclear envelope in association with the fibrous lamina.
• Of the 46 chromosomes present in the human cells, 44 somatic chromosomes are in 22 pairs of structurally similar chromosomes.
• Nucleoli are the synthesis sites for most ribosomal RNA.
• Each nucleosome is composed of 166 base pairs of the DNA strand coiled around a core of 8 histones.