QUESTION 1 10
ncards
ictor
In cell structure and function you learned that calcium ions (Ca2+) are stored in the smooth ER. Some signaling
pathways in the cell cause the ER to release the calcium ions into the cytoplasm, which causes the calcium ion
concentration in the cytoplasm to increase and at the same time the calcium ion concentration in the ER to
decrease. Once the signaling pathway is turned off, the calcium is returned to the ER so that the concentration of
calcium in the ER is very high and the concentration in the cytoplasm is almost zero.
• What membrane transport mechanism would you propose is used to return the calcium ions to the ER and
why?
• Your answer must include:
• What type of membrane protein would be used.
The location of the membrane protein.
• A description of how the membrane protein would be used.
Τ Τ Τ
Arial
• 3 (12pt)
• T-S-E->.is
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Membrane Transport by ion channels.

Explanation:

Stromal interaction molecules STIM1 and STIM2 are membrane proteins localized in the Endoplasmic Reticulum (ER). It has been shown that these proteins play important cellular functions. For example, STIM1 and STIM2 ion channels are involved in the activation of cell surface receptors, being it a specific signaling pathway associated with the store‐operated calcium entry. Calcium ions (Ca2+) in the cytoplasm are released from the ER by STIM1 and STIM2, and this protein activity is required for initiating different cellular processes including apoptosis, migration and cell proliferation.  

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