seminar 5

• cytoplasm: cytosol, cytoskeleton
• cytosol structure: space between organelles, watery-fluid
• cytosol function:

  1. where biochemical processes occur
  2. biochemical intermediates shuttle & converted in transition.
  3. protein biosynthesis
• cytoskeleton structure:


  1.colletion of proteins in cytosol

  2.composed of proteins(not membrane)

  3.act as scaffolds & structural support

  4. composed of 3 types of molecular structures: microfilaments, intermediate filaments, microtubules
• cytoskeleton functions:


  organizes cell's activities, structures & anchors many organelles
• microfilaments:


  structure: actin

  function:

  -maintain shape(tension-bearing)

  -muscle concentration

  -changes in cell shape

  -cytoplasmic streaming

  -cleavage furrow formation during division

  -pseudopodia
• intermediate filaments

  structure: keratins

  function

  -maintain shape(tension-bearing)

  -anchor nucleus

  -anchor other organelles

  -formation of nuclear lamina
• microtubules


  structure: tubulin proteins

  function:

  -maintain shape(girders)

  -move chromosomes in mitosis

  -cilia, flagella

  -move organelles
• Endomembrane system ,fs


  structure: a system of compartments of all membrane-bound organelles in cell. Not include mitochondria, chloroplasts, microbodes

  function: make, pack, ship proteins, molecules by vesicles.
• endomembrane system origin


  may have formed by the invagination of ribosome-bearing plasma membrane around the early nucleus. Then have evolved to full endomembrane system.
• Endoplasmic reticulum (ER)


  • consist of membrane cisternae that ramify throughout the cytoplasm. Result in compartments, channels
  • dynamic structure: always changing function, structure
  • Rough ER: have ribosome / Smooth ER: not have ribosome
  • Rough ER: produces proteins, lipids / Smooth ER: produces majority of lipids. Both produce carbohydrates.
  • Surfaces for synthesizing: proteins, glycoproteins, lipids, carbohydrates.
• Golgi apparatus


  • polar, vesicles arrive at cis face, leave at trans face
  • make, pack, secrete molecule
  • molecules are transferred from ER in vesicles to be biochemically modified.
  • where polysaccharides formed
  • some molecules leave Golgi through secretory vesicles, and leave the cell by exocytosis
  • some molecules are packed into vesicles stay in the cell(lysosomes)
• Plant vacuoles


  -equivalent to lysosomes, surrounded by 1 membrane(tonoplast)

  -consist hydrolytic enzymes, act as degradative compartments

  -break down products, storage nutrients, pigments, maintain the turgor pressure
• lysosomes


  -surrounded by single membrane, recycle bin of animal cell

  -break down the molecules indigested by endocytosis, recycle old organelle

  -acidic interior (pH = 4.5), hydrolytic enzymes derived from ER, Golgi apparatus.

  -digest pathogens enter the cell
• Microbodies


  -same size with lysosome, surrounded by single membrane, recycle bin: animal and plant cell

  -neutral pH

  -hydrolytic enzymes not derived from ER so not a part of endomembrane system

  -2enzymes: peroxisome(breakdown aa), glyoxysome(fatty acids)