CELL STRUCTURES / PARTS

Now that we have settled the cell types, we can now focus on the actual structure of cells.

Prokaryotic Cell Structures

Part	Role
Pili (Pilus)	Hair-like structures used for movement and attachment to surfaces.
Plasmid	Small circular DNA separate from chromosomal DNA.
Ribosome	Synthesizes proteins for the cell.
Cytoplasm	Jelly-like substance where most cellular processes occur.
Cell Membrane	Selectively permeable membrane that controls movement in and out of the cell.
Cell Wall	Provides structure and protection to the cell.
Capsule	Protects bacteria from drying out (present in some bacteria).
Nucleoid	Region containing DNA and controls cell activities.
Flagellum	Enables movement and sensing of the environment.

Figure 2: Bacterial Structures
This is how a bacteria usually looks. Prokaryotic cells do not have a nucleus or membrane-bound organelles.

Eukaryotic Cell Organelles

Organelle	Function
Nucleus	Contains genetic material and controls cell activities.
Endoplasmic Reticulum	Transports materials within the cell.
Rough ER	Produces proteins using attached ribosomes.
Smooth ER	Produces lipids and detoxifies harmful substances.
Ribosome	Produces proteins for use inside or outside the cell.
Golgi Apparatus	Packages and transports substances out of the cell.
Mitochondria	Produces energy (ATP) for the cell.
Vacuole (Animal)	Stores food, water, and waste.
Lysosome (Animal)	Breaks down waste and worn-out cell parts.
Centrioles (Animal)	Helps in cell division.
Cytoskeleton (Animal)	Maintains cell shape and movement.
Cell Wall (Plant)	Provides protection and support to plant cells.
Chloroplast (Plant)	Site of photosynthesis.
Central Vacuole (Plant)	Stores water and maintains cell structure.