3. Do prokaryotic cells have a nucleus? What features are common to all cells?

Prokaryotic cells do not have a nucleus. Instead, their genetic material is located in a region called the nucleoid, which is not membrane-bound. This is one of the key differences between prokaryotic cells (like bacteria and archaea) and eukaryotic cells (like plant and animal cells), which do have a true nucleus enclosed by a nuclear membrane. Common features of all cells, whether prokaryotic or eukaryotic, include: 1. **Cell Membrane**: A phospholipid bilayer that surrounds the cell, providing structure and regulating the movement of substances in and out of the cell. 2. **Cytoplasm**: The jelly-like substance within the cell membrane that contains all the cellular components and is the site of many metabolic processes. 3. **Genetic Material**: All cells contain DNA (or RNA in some viruses) that carries the genetic instructions necessary for growth, reproduction, and functioning. 4. **Ribosomes**: Structures that synthesize proteins by translating messenger RNA (mRNA). Ribosomes are found in both prokaryotic and eukaryotic cells. 5. **Metabolism**: All cells carry out metabolic processes to convert energy and matter to sustain life. These features highlight the fundamental similarities that define cells as the basic units of life.