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Chapter 6B

Chapter 6B. A Tour of the Cell. Other Membranous Organelles, I. Mitochondria - quantity in cell correlated with metabolic activity (the more active, the more mitochondria) Site of cellular respiration Double membranes (phospholipid); cristae/matrix Intermembrane space contain own DNA.

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Chapter 6B

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  1. Chapter 6B A Tour of the Cell

  2. Other Membranous Organelles, I • Mitochondria - quantity in cell correlated with metabolic activity (the more active, the more mitochondria) • Site of cellular respiration • Double membranes (phospholipid); cristae/matrix • Intermembrane space • contain own DNA

  3. Other Membranous Organelles, II • Chloroplast - type of plastid • Double membranous • Thylakoids (flattened disks) • Grana (stacked thylakoids) • Stroma – gel like material around grana • Photosynthesis • Own DNA

  4. Peroxisomes • Single membrane • Produce hydrogen peroxide in cells • Metabolism of fatty acids; detoxification of alcohol (liver) • Hydrogen peroxide then converted to water by catalase

  5. The Cytoskeleton • Fibrous network in cytoplasm • Support, cell motility, biochemical regulation • Microtubules - thickest; tubulin protein; give shape, support, transport, chromosome separation • Microfilaments - thinnest; actin protein filaments; motility, cell division, shape • Intermediate filaments - middle diameter; made of keratin protein; shape, nucleus anchorage

  6. Centrosomes/Centrioles • Centrosome - region near nucleus containing the centrioles • Centrioles - nine sets of triplet microtubules in a ring; used in cell replication; only in animal cells

  7. Cilia/flagella • Locomotive appendages • Ultrastructure: • “9+2” • 9 doublets of microtubules in a ring with 2 single microtubules in center • Connected by radial spokes • Anchored by basal body • Made of dynein protein

  8. Cell surfaces & junctions • Cell wall – in plant, not animal cells • Protection, shape, regulation • Plant cell: • Primary cell wall produced first • Middle lamella of pectin (polysaccharide); holds cells together • In some plants, a secondary cell wall forms; strong durable matrix; wood (between plasma membrane and primary cell wall)

  9. Extracellular matrix (ECM) • Glycoproteins - proteins covalently bonded to carbohydrate • Collagen (50% of protein in human body); embedded in proteoglycan (another glycoprotein-95% carbohydrate) • Fibronectins - bind to receptor proteins in plasma membrane called integrins (cell communication)

  10. Intracellular junctions • PLANTS: • Plasmodesmata: cell wall perforations; water and solute passage in plants • ANIMALS: • Tight junctions: fusion of neighboring cells; prevents leakage between cells • Desmosomes: riveted, anchoring junction; strong sheets of cells • Gap junctions: cytoplasmic channels; allows passage of materials or current between cells

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