Describe the bacterial internal and external cellular structures.

Bacterial cells have both internal and external structures that play important roles in their survival and function.

Internal structures:
1. Cytoplasm: The cytoplasm is a gel-like substance that fills the interior of the bacterial cell. It contains various organelles and structures that are essential for the cell's metabolism and growth.
2. Nucleoid: The nucleoid is a region within the cytoplasm that contains the bacterial chromosome, which carries the cell's genetic information.
3. Ribosomes: Ribosomes are the cellular machinery responsible for protein synthesis. Bacterial cells have smaller ribosomes compared to eukaryotic cells.
4. Plasmids: Plasmids are small, circular pieces of DNA that can replicate independently of the bacterial chromosome. They often carry genes that provide the cell with additional functions, such as antibiotic resistance.
5. Inclusions: Bacterial cells may contain inclusions, which are storage structures that store nutrients or other substances needed by the cell.

External structures:
1. Cell wall: The cell wall is a rigid structure that surrounds the bacterial cell and provides support and protection. The composition of the cell wall varies among different bacterial species, with some bacteria having a thick peptidoglycan layer, while others have a thinner layer or lack a cell wall altogether.
2. Capsule: Some bacteria have a capsule, which is a thick, gelatinous layer that surrounds the cell wall. The capsule helps protect the cell from desiccation, phagocytosis, and other environmental stresses.
3. Flagella: Flagella are long, whip-like appendages that extend from the cell surface and are involved in bacterial motility. They allow bacteria to move towards nutrients or away from harmful substances.
4. Pili: Pili are hair-like appendages that extend from the cell surface and are involved in attachment to surfaces or other cells. Some pili are involved in bacterial conjugation, a process by which bacteria exchange genetic material.
5. Outer membrane: Some bacteria have an outer membrane that surrounds the cell wall. The outer membrane contains lipopolysaccharides and serves as a barrier against certain substances, such as antibiotics.

Internal Cellular Structures:

- Cytoplasm: Gel-like substance that fills the cell and contains all the other cellular structures.
- Ribosomes: Small structures responsible for protein synthesis.
- Nucleoid: Region that contains the cell's genetic material (circular DNA chromosome).
- Mesosomes: Invaginations of the plasma membrane that increase the surface area for metabolic activities.
- Gas vesicles: Structures filled with gas that help the cell float.
- Magnetosomes: Structures that align with the Earth's magnetic field, helping the cell navigate.

External Cellular Structures:

- Cell wall: Rigid, protective layer outside the plasma membrane that provides shape and protection.
- Plasma membrane: Semipermeable membrane that surrounds the cell and regulates the passage of substances.
- Pili: Short, hair-like structures that aid in attachment to surfaces or other cells.
- Fimbriae: Smaller, more numerous pili-like structures that also aid in attachment.
- Flagella: Long, whip-like structures that provide motility.
- Spores: Dormant, resistant structures formed under unfavorable conditions that allow the cell to survive and revive when conditions improve.
- Capsule: Mucopolysaccharide layer outside the cell wall that provides additional protection and adherence.
- S-layer: A protein surface layer that protects the cell from environmental damage and allows for attachment to various surfaces.