Which cell organelle is responsible for storing materials such as water, salts, proteins, and carbohydrates?

The vacuole is the organelle responsible for storing a variety of materials, including water, salts, proteins, and carbohydrates. In plant cells, vacuoles are typically large and can occupy a significant portion of the cell's volume, serving not only as storage compartments but also helping to maintain turgor pressure, which is crucial for maintaining cell structure and function.

In contrast, ribosomes are involved in protein synthesis, converting messenger RNA into polypeptide chains, while the nucleus houses the cell's genetic material and is the center for controlling cellular activities. The endoplasmic reticulum (ER) plays a key role in the synthesis of proteins and lipids but is not primarily involved in storage. Thus, the distinct function of the vacuole in storage differentiates it from these other organelles, making it the correct choice for this question.