Module 4- Membrane bound organelles

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Module 4- Membrane bound organelles
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2015-10-23 02:49:51
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membrane bound organelles
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membrane bound organelles
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  1. what 2 contents in the cell make up most of the cell?
    • cytosol
    • mitochondria
  2. cytosol
    • intracellular fluid
    • makes up about 54% of the cell volume and is composed of water, salts, and organic molecule, protein filaments that make up the cytoskeleton, soluble proteins, ribosomes and proteasomes
  3. organelles
    sub-cellular structures outside the nucleus such as the Golgi, ER, lysosomes etc.
  4. what are part of the endomembrane system?
    endoplasmic reticulum, Golgi, endosomes, and lysosomes
  5. endoplasmic reticulum (3)
    • is a continuous network of flattened sacs, tubules and vesicles through the cytoplasm of a eukaryotic cell
    • ER cisternae: membrane-bound sacs
    • ER lumen: space inside them
  6. compare rough ER and smooth ER.
    • Rough ER: characterized by ribosomes on the cytosolic side of the membrane
    • Smooth ER: lacks ribosomes and has a membranous structure with more space in the lumen to accommodate special molecules
  7. what is the function of transitional elements (TEs)
    • subdomain of rough ER
    • play a role in the formation of transition vesicles that shuttle lipids and proteins from the ER to the Golgi complex
  8. list the 6 functions of the rough ER.
    • involved in the biosynthesis and processing of proteins
    • is the site for initial step of addition of carbohydrates to glycoproteins
    • folding of polypeptides
    • recognition and removal of mis-folded proteins
    • assembly of multi-meric protein complexes
    • role in quality control
  9. describe one of the functions of rough ER: rough ER is involved in biosynthesis and processing of proteins
    • ribosomes on the cytosolic side of the rough ER membrane synthesize both membrane bound and soluble proteins for the endomembrane system
    • newly synthesized proteins are inserted into the endomembrane system through a pore complex as they are synthesized
  10. describe one of the functions of rough ER: rough ER is involved in quality control
    In ER-associated degradation (ERAD), proteins that are incorrectly folded, modified, or assembled are exported for degradation
  11. list the 4 functions of the rough ER
    • drug detoxification
    • carbohydrate metabolism
    • calcium storage
    • steroid biosynthesis
  12. describe one of the functions of smooth ER: Drug detoxification
    • ex. hydroxylation
    • adding hydroxyl groups to hydrophobic drugs increase their solubility, making them easier to excrete from the body
    • hydroxylation catalyzed by a member of the cytochrome p-450 family of proteins called monooxygenases
  13. what happens to the smooth ER when there is a continuous exposure to a drug?
    continuous exposure to a drug can cause rapid increases in the detoxifying enzymes and a proliferation of smooth ER
  14. describe one of the functions of smooth ER: carbohydrate metabolism (2)
    • is involved in breakdown of stored glycogen
    • contains glucose-6-phosphatase, an enzyme unique to smooth ER
    • glucose-6-phosphatase hydrolyzes the phosphate from glucose-6-phosphate to form free glucose
  15. describe one of the functions of smooth ER: calcium storage (2)
    • calcium ions are pumped into the ER by ATP-dependent calcium ATPases and are released when needed for muscle contraction
    • ER lumen contains high concentrations of calcium-binding proteins  
  16. describe one of the functions of smooth ER: Steroid biosynthesis
    • smooth ER in some cells is the site of cholesterol and steroid hormone synthesis
    • large amounts of smooth ER are found in cells that synthesize these
    • smooth ER has also been found associated with plastids in some plants, maybe involved in phytohormone synthesis
  17. describe the process of membrane biosynthesis. (3)
    • fatty acids for membrane phospholipids are synthesized in the cytoplasm and incorporated into the ER membrane on the cytosolic side
    • transferred to the luminal side of the bilayer by enzymes called phospholipid translocators (flippases)
    • phospholipid exchange proteins convey specific phospholipids to mitochondria, chloroplasts or peroxisomes
  18. Golgi complex
    • is a series of flattened membrane-bounded cisternae
    • the Golgi complex lumen (intracisternal space) is part of the endomembrane system
    • series of cisternae usually 3-8 is called a Golgi stack
  19. describe the 2 faces of the Golgi stack.
    • cis face: oriented toward the ER, the Golgi compartment= cis-Golgi network (CGN)
    • medial cisternae: between the cis face and trans face
    • trans face: opposite side, the compartment= trans-Golgi network (TGN)
  20. where do transport vesicles form and are taken in?
    • incoming transport vesicles come to cis face
    • newly forming vesicles form in the trans face
  21. what are the 5 functions of the Golgi complex?
    • modifying, sorting, and packaging proteins for cell secretion (exocytosis) or use within the cell
    • transport of lipids
    • creation of lysosomes
    • production of carbohydrates and proteoglycans
    • possible role in apoptosis
  22. the structure of the Golgi, is it fixed or fluid? What are the 2 models that depict the flow of lipids and proteins through the Golgi complex?
    • The stationary cisternae model:
    • -each cisternae in the Golgi stack is stable structure 
    • -transport of materials from one cisternae to another is mediated by shuttle vesicles
    • -these bud off from one cisternae and fuse with the next cisternae in the cis to trans sequence
    • The cisternae maturation model:
    • -the Golgi cisternae are transient compartments
    • -these gradually change from from CGN through medial cisternae to TGN
    • -enzymes not needed in later compartments are returned to earlier compartments in vesicles
  23. anterograde transport (2)
    • movement of material towards the plasma membrane
    • as a secretory granule fuses with the plasma membrane and discharges its content, a bit of membrane from the ER becomes part of the PM
  24. retrograde transport (3)
    • flow of vesicles from Golgi cisternae back to the ER
    • allows the cell to balance the flow of lipids toward the PM
    • also ensures a supply of materials for forming new vesicles
  25. list the three ways proteins can move from one compartment to another.
    • gates transport
    • transmembrane transport
    • vesicular transport
  26. describe the process of vesicular transport. (4)
    • a membrane enclosed transport intermediate transfers proteins from one compartment to another
    • transport vesicles are loaded with cargo in one compartment (donor)
    • they pinch off
    • they discharge the cargo in another compartment (target)
  27. what are coat proteins?
    what are it's 3 principle functions?
    • coat proteins: proteins on the vesicle surface
    • function:
    • 1. it gathers membrane proteins in a specialized membrane patch, selecting appropriate molecules for transport
    • 2. assembles into a curved basket like a lattice, molding the formation of the vesicle
    • 3. may be involved in interactions with microtubules that help move the vesicle throughout the cell

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