Question

The plasma membrane of all animal cells contain the Na+/K+ pump. If you consider the clathrin-coated vesicles that are bringing this protein from the Trans-Golgi Network to the plasma membrane:

1 Where did the lipids in the membrane of this vesicle first become part of a membrane?

2 Why is the membrane of this vesicle asymmetric, and where was this asymmetry established?

3 What motor protein would you expect these vesicles to interact with? Why?

4 If there are no other proteins in the plasma membrane of the cell yet (this is a very new cell!), could the pump operate right away, or would it need other proteins in the membrane before it could operate? Explain.

Answer 1

1) The lipids in the membrane always from the donor membrane of the organelle .Therefore in this case it is the Gologi apparatus where the lipids in the membrane of the vessicle become part of the membrane .

3) Microtubules help in the movement and transport of vessicle . Mostly dyenin and kinesin are motor protein of microtubules which are responsible for to and fro movement of the vessicle. Here, as it is moving from golgi to plasma membrane, i.e, the movement is occuring from centre to periphery, motor protein dyenin interact will interact with the vesscile for its transportation.

4) For functioning of the Na+/K+ pump , there must be a gradient of ions on both side of the pump. The flow of ions across a membrane is driven by both the concentration and voltage components of an electrochemical
gradient. The new cell has no other protein other than the pump, which mean there is no ion channel for K+ and Na+ for influx of K+ inside the cytoplasm and Na + efflux into extracellular fuild respectively. If this process will not occur , there will be no concentration gradient in response to cellular needs and therefore the pump will not function. So, in order to operate the pump ot required other proteins in the membrane.