Describe how the fluidity of the membrane and how this allows transport across it.

The fluidity of membranes allows it to invaginate and form vesicles. This is important for the process of endocytosis by which the cell is able to uptake materials from the extracellular environment. Vesicles move materials within cells. The fluidity of the membrane also allows vesicles containing materials targeted for secretion outside of the cell to fuse with the plasma membrane. This is important for the process of exocytosis by which the the cell can release materials.