Membrane sacs, known as vesicles, play a crucial role in the transportation of molecules within cells. These small, membrane-bound compartments are essential for moving materials between different organelles, as well as to and from the cell membrane.
Vesicles are formed by the budding off of membranes from larger organelles, such as the endoplasmic reticulum or the Golgi apparatus. They can transport proteins, lipids, and other molecules to their intended destinations, ensuring that cellular processes function smoothly.
For instance, when proteins are synthesized in the rough endoplasmic reticulum, they are packaged into vesicles that then move to the Golgi apparatus for further processing and sorting. After modifications, the proteins are placed into new vesicles that transport them to various locations, including secretion outside the cell or delivery to other organelles.
In summary, vesicles are the key organelles involved in the transport of molecules in cells, facilitating communication and functions among different cellular compartments.