Compartmentalization: Eukaryotes possess membrane-bound organelles like mitochondria, chloroplasts, and the Golgi apparatus, which allow different chemical reactions to occur simultaneously in isolated environments. Prokaryotes lack these structures entirely.
Ribosome Size: Both cell types contain ribosomes for protein synthesis, but they differ in sedimentation coefficient. Eukaryotes have larger 80S ribosomes, while prokaryotes (and eukaryotic mitochondria/chloroplasts) contain smaller 70S ribosomes.
Cell Division: Eukaryotic cells divide via mitosis or meiosis involving a spindle apparatus to separate chromosomes. Prokaryotes divide through binary fission, a simpler process where the circular DNA replicates and the cell splits in two without a spindle.
| Feature | Prokaryotes | Eukaryotes |
|---|---|---|
| Nucleus | Absent (Nucleoid region) | Present (Nuclear envelope) |
| DNA Structure | Circular and 'naked' | Linear and histone-bound |
| Organelles | None membrane-bound | Many (Mitochondria, ER, etc.) |
| Ribosomes | 70S | 80S (cytoplasm) |
| Cell Wall | Murein (Peptidoglycan) | Cellulose (Plants) or Chitin (Fungi) |
| Average Size |
Capsule: A protective outer layer (sometimes called a slime capsule) that prevents the cell from drying out and shields it from the host's immune system. This is a significant virulence factor in pathogenic bacteria.
Flagella: Long, tail-like appendages that rotate like a propeller to provide motility. Unlike eukaryotic cilia or flagella, prokaryotic flagella are made of the protein flagellin and lack a complex microtubule arrangement.
Pili: Hair-like structures on the surface used for attachment to other cells or surfaces. They play a crucial role in bacterial conjugation, where genetic material is transferred between cells.
Structure vs. Size: When asked for structural differences, do not list 'size' as a primary answer. Focus on the presence of a nucleus, the type of DNA, or the composition of the cell wall.
Universal Features: Remember that both cell types possess a cell surface membrane, cytoplasm, and ribosomes. Never claim prokaryotes lack ribosomes entirely.
Cell Wall Specificity: Be precise with terminology; bacterial walls are made of murein (peptidoglycan), while plant walls are cellulose. Using the generic term 'cell wall' is often insufficient for full marks.
Organelle Origins: Note that mitochondria and chloroplasts in eukaryotes contain 70S ribosomes and circular DNA, which is evidence for the endosymbiotic theory.
