Prokaryotes, such as bacteria, are generally smaller and simpler than eukaryotic cells. They are single-celled organisms that lack a nucleus or membrane-bound organelles. Instead, their DNA is located in a region of the cell called the nucleoid.

Surrounding the cell is the plasma membrane, which regulates what enters and leaves the cell. Outside of this is the cell wall, which provides shape, support, and protection, and helps prevent dehydration. Some bacteria also have a capsule (or slime layer), a sticky outer coating that helps them attach to surfaces and offers additional protection.

Inside the cell, ribosomes produce proteins that the cell needs to gather nutrients, grow, and reproduce. The cell’s DNA exists as a single chromosome, which is a long, continuous loop of DNA that contains most of the organism’s genetic information. In addition to this main chromosome, some bacteria contain plasmids, which are small, circular, double-stranded DNA molecules separate from the main chromosome. Plasmids often carry useful genes, such as those that provide resistance to antibiotics.

Some prokaryotes have structures that help with movement and attachment. Flagella are long, whip-like projections that allow the cell to move through its environment. Pili are short, hair-like extensions of the plasma membrane that help bacteria attach to surfaces. They can also act as bridges between cells, allowing bacteria to exchange genetic material.

Review:

1. Describe the purpose of the cell wall.
2. Where is DNA found inside a cell?
3. What is the role of the plasma membrane?