Which best describes the cytoplasm?

• A. A rigid outer layer of the cell.
• B. A water-based suspension containing organelles and metabolic substances.
• C. The site of DNA storage.
• D. The energy-producing center.

Answer: (B)

The cytoplasm is the jelly-like interior of the cell, the fluid space between the plasma membrane and the nucleus. It is mainly water (cytosol) that suspends organelles and dissolved nutrients, creating the environment where many metabolic activities take place. That’s why describing it as a water-based suspension containing organelles and metabolic substances fits best. The other descriptions point to things outside this definition: a rigid outer layer refers to the cell boundary or cell wall, the site of DNA storage is the nucleus (with some DNA in mitochondria), and the energy-producing center is mitochondria themselves, not the cytoplasm as a whole.