Plasma Membrane

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sweetz2go
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44730
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Plasma Membrane
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2010-10-25 03:53:13
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Biology
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Plasma Membrane
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  1. What are the components of the plasma membrane?
    Plasma Membrane = Lipid ( cholesterol, phospholipid, glycolipids ) + Protein ( ID, enzymes, receptors, channels, carriers, cytoskeleton )

  2. Explain how the amphipathic nature of the phospholipid molecules results in the formation of the plasma membrane.
    • each molecule consists of a hydrophilic (water-loving) portion and a hydrophobic
    • (water-hating) portion. Due to the amphipathic nature and insolubility
    • in water, phospholipids are ideal compounds for forming the biological
    • membrane.
    • The fatty acid part minimize interaction with the water because it is
    • hydrophobic which is non polar. While the Hyrdophilic head (polar) is
    • faced outward because it loves water.
  3. Define selective permeability.
    Allows some things to go in/out depending on phosphilipid properties.
  4. Define Fluidity
    Sideways motion of proteins/fats across plasma membrane.
  5. Explain how the phospholipid bilayer affects the selective permeability and fluidity of the plasma membrance.
    • For selective permeability, Small, uncharged and non-polar molecules can get across.Large polar molecules and ions can't get across.
    • Reduced fluidity= making all fatty acids saturated .Increase Fluidity= fatty acids have to be unsaturated
  6. Explain why the fluidity is an important property of the plasma membrane.
    • - cell division ex. cytokinesis
    • - medicine ex. artifical fertilization
  7. Explain how plant cells cope with temperature changes in thier environment.
    • They change the fat content of the plasma membranes.
    • Increase fluidity= increase the amount of saturated fatty acids, reduces fluidity, make fat saturated ( hot summer )
    • Decrease fluidity= ( membrane can freeze ) -> increases the amount of unsaturated fatty acids ( cold winter )
  8. How does cholesterol act as a " temperate buffer " for the plasma membrane?
    • 20% of plasma membrane.
    • - it resist chanes in fluidity
    • - it strengthens plasma membrane
    • At warm temperatures, cholesterol restrains the movement of phospholipidsand reduces fluidity
    • .• At cool temperatures, cholesterol maintains fluidity by preventing tight packing.
  9. Explain why Glycolipids are an essential component of the plasma membrane.
    • " nametags" of the cell, identiflies cells, cell identity markers
    • ex. organ transplant ( liver, heart,lungs,lens of eye,skin) why is it rejected sometimes?
    • Its because of the differences in glycolipid
  10. Explain some of the important roles of proteins in the plasma membrane.
    • Transport proteins: movement of specific substances into or out of cells-
    • Enzymes, sometimes catalyzing one of a number of steps of a metabolic pathway-
    • Receptors, which relay hormonal messages to the cell
    • Cytoskeleton anchors
    • Identity markers
  11. What are the cause and consequences of diabetes mellitus?
    • Cause: affects plasma protein, pancreas doesnt produce enough insulin, # of glucose carriers drops, blood sugar levels go up
    • Cosequences: cells starve, can't get sugars in cell, high sugar levels in urine
  12. Explain how the shape of red blood cells is maintained by plasma membrane proteins.
    • The position of the proteins along the plasma membrane serves a purpose
    • as they function in anchoring the cytoskeleton within the cell. The
    • cytoskeleton gives the specific structural shape to the cells, which
    • ranges from the simple disc shaped red blood cells to the complex
    • structure of neurons.
  13. What is tight junction? function?
    • web like arrangement of membrane proteins that encircle the cell
    • Function : prevents leakages of fluids btwn cells
  14. what is plasmodesmata? function?
    • " cytoplasmic " connections btwn plant cells.
    • it allows communication btwn cells
  15. What are Desmosomes? function?
    • localized, protein linkages that are reinforced by intermediate fibers.
    • it anchors and prevents cells from falling apart
  16. what are gap junctions? function?
    • are open protein channels btwn cells.
    • They allow for cells to communicate.
    • Important for food to be moved down to stomach
    • ex. peristalisis
  17. Difference btwn Passive and active process.
    • Passive: High to low conc. requires no energy(ATP), concentration gradient
    • Active: Low to high conc. Requires ATP, protein->pump, against conc. gradient
  18. Difference btwn diffusion and faciliate diffusion.
    • DIFFUSION:the process
    • by which molecules spread from areas of high concentratiion, to areas
    • of low concentration

    facilitated diffusion:"needs help" needs an ion pump or a protein channel
  19. Plasma membrane transport= Passive ( diffusion, facilitated diffusion, osmosis ) + Active ( primary, secondary, bulk )
  20. Define osmosis.
    • form of diffusion.
    • passage of free water from low solute to high solute conc. across a selected permeable membrane.

  21. Explain how solutes affect osmosis.
    • inverse relationship
    • The more solute, the more it reduces the # of free water molecules.
  22. what is kwashiorkor?
    • a form of malnutrition caused by inadequate protein intake
    • - rejected ones, mother stopes breast feeding them
    • - stops taking in milk, stops taking in protein(solute)
  23. How does hypotonic, isotonic, and hypertonic solutions affect animal and plant cells?
    • hypotonic: high solute conc around cell than inside cell ( free water comes out, inside cell will swivle )
    • Isotonic: same solute conc. inside and outside cell ( animal cells do well )
    • Hypertonic: lower solute conc. compared to within cell ( plant cells do well )

  24. How would u expect prokaryotes to become affected in hypotonic, isotonic, and hypertonic solutions?
    • Animal cell=
    • Hypotonic: Lysis, bursts/destruction
    • Isotonic: normal
    • Hypertonic: Crenation

    • Plant cell=
  25. what are active processes?
    • all use energy in form of ATP, use membrane protein, moving things against
    • conc, gradient, low to high conc.
  26. What is primary transport?
    • also called direct active transport, directly uses energy to transport molecules across a membrane
    • It expends ATP energy to move sodium ions out of the cell and replace them with potassium ions.
    • outside= more positive , inside= more negative
    • every 3NA+ pumped out for 2K+ pumped in
  27. what is secondary transport?
    • -use of ATP indirectly
    • -cotransporter=moving H+ and sucrose at the same time b/c we are using hydrogen ion conc. difference
    • -Exchangers move two or more molecules in opposite directions. ( Na and H )

  28. Why is the action of the sodium-potassium ATPase pump essential for life?
    • it is most inportant pump in body, its how electrical signals happens in brain and nerves
    • - for nerve impulses
  29. Explain how cyanide poisoning causes death.
    • -cant find cyanide in blood, only through hair folicles
    • -The cyanide shuts off the power generater of cell
    • -pumps shut off (Na+ dont go out and K+ dont go in anymore )
    • - charge difference dissapears and then heart muscles and brain stops
  30. Define Bulk transport.
    movements of large amount of substance in/out of cell all at once; using vesicles
  31. Difference btwn endocytosis and exocytosis.
    • endocytosis: , the cell engulfs some of its extracellular fluid (ECF) including material dissolved or suspended in it.
    • exocytosis: is a cellular process where cells eject waste products or chemical
    • transmitters (such as hormones) from the interior of the cell

  32. Difference btwn Phagacytosis, Pinocytosis, and recptor-mediated endocytosis.
    Phagocytosis: selective Cell eats(ingulfs) large particles ex. backteria, food particle

    Pinocytosis: non-selective, no receptors, cell bringing in fluids with dissolved particles inwards

    Receptor-mediated endocytosis: selective, receptor involed, bulges inwards, brings in dissolved fluids and vitamins

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