Which of the following is NOT a component found in all cells?

The nuclear envelope is not a component found in all cells because it is a structure specifically associated with eukaryotic cells. Eukaryotic cells, such as those in plants, animals, fungi, and protists, have a distinct nucleus enclosed by a nuclear envelope, which protects the genetic material inside.

However, prokaryotic cells, which include bacteria and archaea, lack a true nucleus and consequently do not possess a nuclear envelope. Instead, their genetic material is typically found in a region called the nucleoid, which is not separated from the rest of the cell by a membrane.

In contrast, ribosomes, cytosol, and the nucleus (when talking about eukaryotic cells specifically) are components found in all cells. Ribosomes are essential for protein synthesis and are present in both prokaryotic and eukaryotic cells. Cytosol, the fluid portion of the cytoplasm, is also universal across all cell types, serving as a medium for organelles and biochemical processes. The nucleus is a defining feature of eukaryotic cells, emphasizing that not all cells can be categorized the same way when discussing cellular components.