In lab you are studying the lipid components of cell membranes. You discover two
ID: 166154 • Letter: I
Question
In lab you are studying the lipid components of cell membranes. You discover two novel, uncharacterized phospholipids, which you call PX and PZ. You decide to Investigate the behavior of PX and PZ by labeling the head group of each phospholipid. This label is stable when the lipid resides in the outer leaflet but is degraded when the lipid resides in the inner leaflet. You incorporate labeled versions of PX and PZ specifically into either the inside or the outside of the cell and monitor the change in signal Intensity of these lipids in the plasma membrane. Your data is shown in the figures below. A. In 1-2 sentences, explain what happened in the PZ experiment that did not happen for PX? How did this occur? B. From only this data, can you determine in which leaflet PX and PZ most probably reside in a native cell? Why or why not? If so, what is your determination? Please limit your response to 2-3 sentences.Explanation / Answer
(A) The signal intensity of the labeled lipids incorporated outside the cell and inside the cell is almost equal. It might mean two things
1. The labelled PZ did not get incorporated in to the plasma membrane
2. PZ lipid is exclusively an outer leaflet phospholipid ( since the intensity decreases if goes to the inner leaflet)
(B) PX- is an inner leaflet phospholipid; We can deduce this by the way the signal intensity is slowly reducing with time, which might mean that the phospholipid PX is getting integrated in the inner leaflet
PZ- might be an outer leaflet phospholipid; There is no change in the signal intensity with time. We have to be bit careful with this deduction, since the non-inclusion of PZ into the plasma membrane will also give the same data. We might have to reconfirm by lebelling with another marker that has similar properties ( ie signal when in outer leaflet, but no signal in inner leaflet) or with reverse properties (signal in inner leaflet, but no signal in outer leaflet).
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