2010 CELL II complete +lab - Cell Structure II Diane L.M....

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Cell Structure II Diane L.M. Hickson-Bick, Ph.D. Reading : Gartner and Hiatt Chapter 1; Junquiera Basic Histology, Chapter 3; Klein and McKenzie pp 47-58 and look at first 3 chapters too Objectives : Understand the arrangement and function of the components of the cell’s nucleus. Understand the elements of cell division and the cell cycle. Describe the multiple forms of cell death. Describe the function and composition of cell surface specializations Describe composition and function of different intercellular junctions. Key Words : Nucleus, chromatin, cell division, cell death, cell cycle, microvilli, intercellular junctions, basement membrane, basal lamina. THE CELL NUCLEUS The nucleus houses the genetic machinery. It does not synthesize protein. Usually a round or elongated structure, often at the center of the cell. Main components are: nuclear envelope , chromatin , the nucleolus , and nuclear matrix. A. Nuclear Envelope 2 parallel unit membranes separated by a space called the perinuclear cisterna. Impermeable to ions and proteins of all sizes. Internal membrane associated with the fibrous lamina = 3 main proteins, lamins A, B and C. In non-dividing cells chromosomes are associated with the fibrous lamina. Polyribosomes attached to outer membrane. Inner and outer membranes fuse at nuclear pore. Nuclear pores provide pathways between nucleus and cytoplasm. Complex protein structures ~150nm in diameter; >100 proteins. B. Chromatin Coiled strands of DNA bound to basic proteins (histones) Two types of chromatin distinguishable in non-dividing cells. Rat Pituitary Cell EM n = nucleolus NE = nuclear envelope N = Nucleoplasm GA = Golgi apparatus rER = rough endoplasmic reticulum.
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Heterochromatin = electron dense and appears as coarse clumps in electron microscope or basophilic clumps by light microscopy. Composed of unexpressed DNA Euchromatin = Less coiled portions of chromosomes and visible as finely dispersed granular material. Site of active transcription. In dividing cells chromosomes become supercoiled and densely staining Human cell has 22 pairs of chromosomes grouped by size and position of the centromere and 2 sex chromosomes = diploid state. In female cells one X chromosome remains euchromatic while other remains condensed and inactive. C. Nucleolus Spherical structure up to 1mm in diameter. Rich in rRNA and protein All protein components synthesized in the cytoplasm and imported. 3 basic components seen by EM: Nucleolar organizer DNA: Base sequences coding for rRNA Pars Fibrosa: Densely packed ribonucleoprotein fibers, primary transcripts of rRNA genes Pars Granulosa: 15-20nm granules representing maturing ribosomes. CELL DIVISION (MITOSIS)
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This note was uploaded on 12/25/2010 for the course MSI 1 taught by Professor Rogerj.bick during the Spring '10 term at University of Texas Health Science Center at San Antonio.

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2010 CELL II complete +lab - Cell Structure II Diane L.M....

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