Which of the following is NOT a component of bacterial cells?

In bacterial cells, the structure known as the nucleus that is found in eukaryotic cells is absent. Instead, bacteria possess a nucleoid region where their genetic material, usually a single circular strand of DNA, is located. This is significantly different from eukaryotic cells, which have a distinct and membrane-bound nucleus.

Bacterial cells do have other essential components such as the cell membrane, ribosomes, and cytoplasm. The cell membrane serves as a barrier that controls the entry and exit of substances, ribosomes are crucial for protein synthesis, and cytoplasm is the gel-like substance that contains all the cellular components and where many metabolic reactions occur. Thus, the presence of a nucleus is not characteristic of bacterial cells, making that the correct answer to the question.