Final answer:
The endoplasmic reticulum (ER) is involved in protein synthesis and intracellular transportation. It does not produce ATP.
Step-by-step explanation:
The endoplasmic reticulum (ER) has several functions, but it does not produce ATP.
One of the main functions of the ER is to synthesize proteins. The rough endoplasmic reticulum (RER), which is studded with ribosomes, is responsible for the production of proteins. The ribosomes attached to the RER make proteins that are then transported from the ER.
Additionally, the ER is involved in intracellular transportation. Molecules, such as proteins, can move from place to place inside the ER, similar to an intracellular highway. The ER also plays a role in lipid synthesis, where it produces lipids. However, the production of ATP is not a function of the ER.