Fundamentals 1- Membranes and Cytoplasm

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Fundamentals 1- Membranes and Cytoplasm
2012-01-09 19:21:17
Cell Bio

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  1. Explain the difference between integral and peripheral proteins
    • Integral proteins:
    • 1. span the entire length of the membrane completely (20AA)
    • 2. Removed by Detergent

    • Periphral Proteins:
    • 1.Ionicly bind to lipids or other proteins and do not penetrate the bilayer
    • 2. Removed with high salt (1mol NaCl)
    • 3. located on both extracellular(made in ER and secreted) and intracellular (made in cytoplasm)
  2. What are the 3 types of integral proteins and explain. What makes them integral proteins?
    1. Transmembrane proteins- a-helix domain completly spans the membrane and can make a single pass or multiple passes

    • 2. Partially penetrating proteins- all the protein is on the same side of the membrane
    • ex: Caveolin caveolae

    3. Covalently tethered proteins- are covalently linked to the membrane through glycolipids or phospholipids

    All are integral proteins because all of them are removed using detergent.
  3. What are the 3 types of inclusions? What makes them inclusions?
    1. Fat droplet- found in adipocytes, adrenal cortex cells, liver cells.

    2. Glycogen granules- storage sites for glucose found mainly in the liver cells

    3. Lipofucin granules- in aged, non-dividing cells like neurons and muscle cells. usually golden brown in colors and can be membrane bound because they start as lysosomes but cannot break down any more.

    An inclusion is something in the cell usually non-membrane bound with the exception of lipofuscin granules that have no function in the cell and are accumulated metabolites.
  4. Why do antiboitics kill bacteria but not our cells?
    • The Bacteral have a different structures that are unique to it and not found in eukayotic cells
    • 1. Ribosomes-the 30S and 50S units are targets for certain antibiotics and inhibiting these they inhibit the protien synthesis and kill the bacteria

    2. Cell wall- eukayotes do no have a cell wall so targeting this will kill the bacteria because it has no barriers ex- vancomycin and penicillin
  5. What is an antibotic?
    Antibiotic- a soluble substance that is derived from a mold or bacterium that inhibits the growth of other microorganisms
  6. Why do we feel sick after taking some antibiotics
    • The Mitochondrial Origin Theory
    • Mitochondria were bacteria that were engulfed by the cell in the very beginning. Mitochondria were aerobic and used the O2 of the cell to make ATP so it adapted to living with the cell.

    The mitochondria encodes for its own ribosomes of 30S and 50S the same as the bacteria.

    The antibiotics that target these in bacteria can leak through the double membrane in small quantities and destroy our own ATP making mitochondria which can make us feel unwell and out of energy.
  7. What composes the Plasma Membrane of the eukaryotic cell?
    1. Phospholipids- polar head (hydophilic) and non-polar tails (hydrophobic) create a bilayer for protection and regulation of what goes in and out of the cell

    2. Cholesterol- Helps maintain the fluidity of the membrane. Increased colesterol --> less fluid the membrane and harder for things to get in and out of the cell

    3. Proteins- integral and peripheral proteins that are in a mass ratio of 1:1 to phospholipids
  8. what composes the phospholipid?
    • 1.Glycerol backbone
    • 2. 2 non-polar fatty acid hydrocarbon chains
    • 3.the phosphate containing polar group
  9. what do you call a phospholipid that has a head group of:
    1. choline 2. serine 3. Ethanolamine 4. inositol
    which of these is charged and where is it located?
    • 1. phosphatidylcholine
    • 2. phosphatidylserine
    • 3. phosphatidylethanolamine
    • 4. phosphatidylinositol

    Phosphatidylethanolamine is neg charged and is found on the inner membrane of the cell
  10. what are some characteristics and functions of choloesterol
    • steriod
    • lipid-soluble
    • found in both leaflets of the membrane
    • amphiphilis- OH forms the polar head
    • synthesized in the ER
    • Can flip easily in the membrane unlike phospholipids because of its small polar head group

    • Functions:
    • 1. they keep the structure of the hydrocarbons of the phospholipids so a cell wall is not needed

    2. they make the membrane less soluble to small water molecules

    3. they prevent crystalization of hydrocarbons when lowering the temp which doesnt happen in the body
  11. what movements can phospholipids and cholesterol do in the membrane?
    Phospholipids can move laterally and can rotate in a circular motion, flex, but cannot flip to the other leaflet because their polar heads are large. Therefore they are asymetrical in the leaflets of the membrane. what is on one leaflet is not on the other

    Cholesterol flips easy because it has a small polar head group. Therefore the cholesterol is 50/50 on inner and outer membrane leaflets
  12. how long does it take a lipid molecule to diffuse into the membrane of a Eukaryotic cell?
    about 10 seconds to diffuse throughout the membrane
  13. saturated vs unsaturated fatty acids tails of phospholipids membrane
    If the tails are saturated that means there are no double bonds in the hydrocarbons and that they are closely packed together and are ridgid

    If the tails are unsaturated that means there are double bonds are there are kinks in the hydrocarbons making the membrane more fluid.
  14. In a transmembrane protien, if something binds to one end of the protein (intracellular or extracellular) what happens to it?
    • It can elicit a conformational change in the protein on the opposite end of the binding.
    • ex: if insulin binds to the receptor on the extracelular side of the protein, it can then have a conformational change in the protein on the intracellular side to elicit a responce

    This is called the 2nd messenger pathway
  15. What are glycoproteins and glycolipids? how are they synthesized? where are they found?
    • glycoprotein= carbohydrate+protein
    • glycolipid= carbodydrate + lipid

    when lipids and proteins are being sythesized in the ER sometimes carbohydrates can attach to them during the process

    carbohydrates are always located on the extracellular leaflet of the bilayer
  16. What is the membranes function? why does the cell need a membrane? why do organelles have a membrane?
    The membrane functions as not only structure but protection and a regulatory site.

    It gives the cell a way to monitor what comes in and out of the cell

    The cell can also create its own microenvironments and compartmentalize its functions (organelles)

    each of the organelles has a specific function and only specific molecules need to be involved to make the cell more efficent.
  17. What is a cells resting membrane potential? What composes this? Are the ions in the extracellular/intracellular the same? amounts?
    The resting membrane potential of a cell is usually around -60mV.

    It is negitive because of the ion concentrations on both sides of the membrane

    Na, K, Cl and Ca are the 4 main ions that contribute to this negitive charge inside the cell

    Both inside and outside the membrane has the same ions but in different concentrations
  18. because phospholipids are fluid throughout the membrane, how can this lateral movement be restricted?
    Bacteria- forms large aggregates

    Humans- they are hooked on the something outside the cell : Extracellular matrix, inside the cell: cytoplasmic matrix, or they can be hooked on proteins of other cells around it.
  19. what is a lipid raft?
    an area of the membrane in which it has thickend and more sphingomyelin and cholesterol and some proteins have concentrated

    only specific and longer transmembrane protiens can accumulate here.

    they also can form plasma membrane organelles called caveolae
  20. what are the only 2 organelles that have a double membrane?
    nucleus, mitochondria