Chapter 12.6

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  1. ·         Some bacteria only have __ and others have __
    o   The inner membrane is the __; and the outer membrane and cell wall provides __
    o   The outer membrane is quite permeable to small molecules, owing to the presence of __
    §  The region between the two layers = __
    • one membrane surrounded by a cell wall
    • two membranes separated by a cell wall between them
    • permeability barrier
    • additional protection
    • porins
    • periplasm
  2. ·         Eukaryotic cells don’t have __, and their cell membranes have a __
    ·         In plant cells, the cell wall is outside
    ·         Eukaryotic cells differ from prokaryotes due to presence of __
    • cell walls
    • single lipid bilayer
    • membranes inside cell that form internal compartments, like organelles
  3. o   The outer membrane, similar to bacterium, is quite __, whereas the inner membrane is not in __, which evolved from bacteria by endosymbiosis
    o   The nucleus is surrounded by a __; and, the ER is another example
    • permeable to small molecules
    • mitochondria
    • nuclear envelope
  4. ·         Thus, eukaryotic cell contains interacting compartments, and __ is essential to many biochemical processes
    ·         Membranes must be able to __so cells can take up, transport, and release molecules
    o   Many cells take up molecules through __, where a protein or larger complex initially __--> boundà specialized proteins act to cause membrane to invaginate
    • transport into and out of these compartments
    • separate or join together 
    • receptor-mediated endocytosis
    • binds to a receptor on the cell surfaceà
  5. §  One of these proteins is __, which polymerizes into a __ around the growing membrane bud, often referred to as a __
    o   The invaginated membrane __ to __
    o   The opposite reaction, __, is a key step in the release of neurotransmitters from a neuron into the synaptic cleft
    • clathrin
    • lattice network
    • clathrin-coated pit
    • breaks off to form a vesicle
    • fusion of the vesicle to the membrane
  6. ·         Ex: Iron is critical to proteins, but free iron ions are __ to cells owing to their ability to __
    o   So, transport of iron atoms from the digestive tract to cells where they are most needed must be tightly controlled
    o   In the blood, iron is __, which can bind two Fe3+ ions; and, cells that need __ to express the __ in their membranes
    • highly toxic
    • catalyze the formation of free radicals
    • bound tightly to transferrin
    • iron
    • transferrin receptor in their membranes
  7. ·         Formation of a complex between the __ and __ initiates __, internalizing these complexes within vesicles called __
    o   As the endosomes mature, proton pumps within the vesicle membrane __
    • transferrin receptor and iron bound transferrin
    • receptor-mediated endocytosis
    • endosomes
    • lower the luminal pH to about 5.5.
  8. §  Under these conditions, the affinity of iron ions for __ is __; these ions are __and are free to pass through channels in the __ into the cytoplasm.
    §  The __ is recycled to the plasma membrane, where __is __ and the __ can __
    • transferrin 
    • reduced
    • released 
    • endosomal membranes
    • iron-free transferrin complex
    • transferrin 
    • released back into the bloodstream
    • transferrin receptor
    • participate in another uptake cycle
  9. ·         Although budding and fusion seem simple, the structures of the intermediates are not
    o   Key membrane components called __ help draw appropriate membranes together to initiate the __.
    §  These proteins, encoded by gene families in all eukaryotic cells, largely determine the __
    §  The specificity of membrane fusion ensures the __
    • SNARE proteins
    • fusion process
    • compartment with which a vesicle will fuse
    • orderly trafficking of membrane vesicles and their cargos through eukaryotic cells
Card Set
Chapter 12.6
Test Three
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