Final answer:
The statement that transport vesicles move from the ER to the medial Golgi network, then through the cis-cisternae before exiting through the trans-Golgi network is false. Transport vesicles actually move from the ER first to the cis face of the Golgi, then through the medial Golgi, and finally, leave through the trans-Golgi network after processing.
Step-by-step explanation:
The statement provided is false. When transport vesicles depart from the endoplasmic reticulum (ER), they first arrive at the cis face of the Golgi apparatus, not the medial Golgi network as suggested by the question. Here, these vesicles fuse with the Golgi membrane and release their contents into the lumen of the Golgi apparatus for processing. Then, the proteins and lipids move through the Golgi apparatus, starting with the cis-Golgi network, progressing through the medial-Golgi region, and finally reaching the trans-Golgi network. During this progression, their contents undergo a series of modifications, such as glycosylation and phosphorylation.
One of the most common modifications is the addition of short chains of sugar molecules, which helps in sorting and tagging the molecules for their final destination. For instance, the addition of mannose-6-phosphate signals proteins to be transported to lysosomes. After the modification process is complete, these proteins and lipids are packaged into vesicles that bud off from the trans face of the Golgi apparatus. These vesicles then either become secretory vesicles that release their contents outside the cell or transport vesicles that deliver their contents to various subcellular locations such as lysosomes, the plasma membrane, or other organelles.