Festus

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Cards (27)

  • Lysosomes are membranous vesicles that are formed in the Golgi complex
  • Lysosomes are filled with digestive enzymes and pump in H+ ions until the internal pH reaches 5.0
  • Functions of lysosomes include:
    • Digest foreign substances
    • Recycle own organelles through autolysis
  • Lysosomal damage can occur after death
  • Primary lysosomes, derived from coated vesicles released from the Golgi apparatus, contain about 60 hydrolytic enzymes
  • Coated vesicles from receptor-mediated endocytosis deliver their contents to a vesicle called an endosome, which fuses with a primary lysosome to form a secondary lysosome
  • H+ - ATPase in the lysosome membrane pumps protons into the intralysosomal space, producing a pH of about 5.0 which activates the lysosomal enzymes
  • Phagocytic vesicles (phagosomes) also fuse with primary lysosomes to form secondary lysosomes for digestion of ingested material
  • Residual bodies containing non-degradable material may remain after digestive activity, and they are retained within the cell and may accumulate
  • Lysosomes are involved in heterophagy, the digestion of extracellular material, and autophagy, the degradation of material of intracellular origin such as mitochondria and ribosomes
  • The lysosomal membrane is resistant to digestion by lysosomal enzymes and impermeable to enzymes and their substrates, but permeable to low molecular weight products of hydrolysis
  • Lysosomes play important roles in clinical and medical aspects of biochemistry, such as in phagocytic cells in lung and liver tissues for digesting foreign materials
  • Silicosis is a condition caused by the inhalation of silica particles into the lungs, leading to reactions between silica and lysosomal membranes, rupture of the membrane, release of lysosomal enzymes, and death of phagocytes
  • Silicosis, asbestosis, and black lung disease are conditions caused by inhaling silica particles, asbestos fibers, and coal dust respectively, leading to fibroblasts depositing collagen fibers, decreasing lung elasticity, impairing breathing, and contributing to the pathology of the diseases
  • The absence of specific hydrolase enzymes from lysosomes can lead to the accumulation of substrate for that enzyme within the lysosomes, resulting in severe medical consequences
  • Nucleus:
    • Large organelle with double membrane nuclear envelope
    • Outer membrane continuous with rough ER
    • Perforated by water-filled nuclear pores
    • Contains nucleolus, which is a spherical, dark body within the nucleus and the site of ribosome assembly
  • Function of Nucleus:
    • Contains 46 human DNA chromosomes with genes that direct synthesis for specific proteins
    • Non-dividing cells contain nuclear chromatin (loosely packed DNA)
    • Dividing cells contain chromosomes (tightly packed DNA that doubles copies itself before condensing)
  • Protein synthesis:
    • Instructions for making specific proteins are found in the DNA
    • Transcribe information onto a messenger RNA molecule
    • Translate the "message" into a sequence of amino acids to build a protein molecule
  • In eukaryotic organisms, DNA is protected in the nucleus with a surrounding envelope consisting of a double membrane separated by a perinuclear space
    • Nuclear envelope interrupted by pores surrounded by highly organized annulus
    • Molecules bigger than nuclear pores can pass through, while smaller molecules are prevented from entering
    • Nuclear proteins are produced in the cytosol but must accumulate in the nucleus for functional reasons
  • Nucleolus:
    • Membrane-less organelle within the nucleus that manufactures ribosomes
    • Looks like a large dark spot within the nucleus
    • Nucleoli are sites of synthesis of rRNA molecules and assembly of ribosomal subunits
    • Some studies suggest the nucleolus may be involved in cellular aging and affect organism senescence