Final answer:
Microtubules (MTs) involved in transport between the endoplasmic reticulum (ER) and the Golgi apparatus are oriented with the minus end toward the ER, option b. This directional orientation is crucial for the transportation of vesicles carrying proteins and lipids from the ER to the Golgi for processing and sorting.
Step-by-step explanation:
The question pertains to the orientation of microtubules (MTs) that facilitate the transportation between the endoplasmic reticulum (ER) and the Golgi apparatus. The correct answer to the question of how MTs between the ER and the Golgi are oriented is that the minus end is toward the ER; therefore, option b. Minus end toward ER is the correct choice.
Vesicles carrying proteins and lipids pinch off from the ER and move towards the Golgi apparatus, fusing with the cis face, also known as the receiving side, of the Golgi. Here, the contents undergo processing and modification before being sorted and directed to their final destinations. Microtubules play a crucial role in the transportation of these vesicles, and their orientation, with the minus end anchored at the ER and the plus end extending towards the Golgi, is essential for the directional movement of the vesicles.