Question

When the transport vesicle shown below fuses with the plasma membrane, which monolayer will face the cell cytosol?

orange outside ring
blue inside ring
light blue inside

-half the time the orange monolayer will face the cytosol, and half the time the blue monolayer will face the cytosol
-the orange monolayer will face the cytosol
-the blue monolayer will face the cytosol
-it depends on whether the vesicle is coming from the endoplasmic reticulum or the Golgi apparatus
-it depends on the vesicle is carrying

Answer 1

The monolayer of the transport vesicle that was facing the cytosol as it formed will face the cytosol when it fuses with the plasma membrane. If the 'orange' monolayer represents this inner layer during formation, then the orange monolayer will be the one facing the cytosol.

Step-by-step explanation:

When a transport vesicle fuses with the plasma membrane, the monolayer that will face the cell cytosol is the monolayer that was facing the cytosol when the vesicle was formed at the endoplasmic reticulum (ER) and then the Golgi apparatus. As the vesicle moves through the endomembrane system, it maintains the same orientation. Therefore, the outer layer of the vesicle (the one facing the cytosol) will fuse with the plasma membrane's cytosolic side, becoming part of the inner leaflet of the plasma membrane. Consequently, if we consider the 'orange' monolayer as the one facing the cytosol during vesicle formation, the orange monolayer will face the cytosol when the vesicle fuses with the plasma membrane.