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  • Created by: jo bill
  • Created on: 21-12-14 13:10

calcium ions

  • ca2+ binding can alter the local electrostatics within a protein bacause of its shape and charge
  • this can cause a conformational change in protein which can alter the surface/structure of the protein
  • therefore, ca2+ can mediate signaltransduction within a cell

calcium homeostasis

  • the concentration of free Ca2+ within the cytosol of the cell is tightly regulated
  1. extremely high levels are toxic and lead to cell death
  2. reduce background noise - so Ca2+ can act as a second messenger

a resting cell

  • the Ca2+ concentration is low in the cytosol
  • ca2+ pumps and Ca2+ exchangers
  • ca2+ pumps incude:
  1. plasma membrane Ca2+ATPase (PMCA)
  2. smooth endoplasmic Ca2+ATPase (SERCA)
  • Ca2+ exchangers include:
  1. Na+/Ca2+ exchanger (NCX)
  2. Na+/Ca2+/K+ (NCKX)

calcium entry

  1. volatge gated Ca2+ selective channels (CaV)

a change in voltage can cause each channel to conduct roughly a million Ca2+ ions per second down the 20,000-fold gradient

2.transient receptor potential (TRP) ion channels

  • located in the plasma membrane
  • permeable to cations
  • sensory tranduction

3. Ca2+ release activated calcium (CRAC) channels

  • located in the plasma membrane
  • a component of this channel - ORAII
  • ORAII is able to interact with a second protein - STIMI
  • STIM I is able to detect when ER Ca2+ is low
  • STIMs can also activate some TRPs

-so this pathway is used to replenish ER Ca2+…


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