Ribosome Facts
| Type | Coefficient | Subunits | Location |
|---|---|---|---|
| 70S | 70 Svedberg | 50S + 30S | Prokaryotes, Mitochondria, Chloroplasts |
| 80S | 80 Svedberg | 60S + 40S | Eukaryotic cytoplasm |
Formula rule: S units are NOT additive (50+30 ≠ 80; this is because sedimentation rate depends on shape + density, not just mass).
Cell Size Formula
- Prokaryote: 1–10 µm (average ~2–5 µm)
- Eukaryote: 10–100 µm (average ~20–30 µm)
- Surface Area : Volume ratio decreases as cell size increases → limits maximum cell size
Key Dates (NEET-tested)
| Year | Event |
|---|---|
| 1665 | Robert Hooke coins term "cell" (cork cells) |
| 1838–39 | Schleiden (plants) & Schwann (animals) formulate Cell Theory |
| 1855 | Virchow adds "Omnis cellula e cellula" |
| 1972 | Singer & Nicolson propose Fluid Mosaic Model |
| 1967 | Lynn Margulis proposes Endosymbiotic Theory |
Organelle Quick Reference
| Organelle | Membrane | Key Function | NEET Nickname |
|---|---|---|---|
| Lysosome | Single | Intracellular digestion | "Suicide bags" |
| Mitochondria | Double | ATP production (oxidative phosphorylation) | "Powerhouse" |
| Golgi apparatus | Single | Package + modify proteins | "Post office" / "Traffic police" |
| Ribosome | None | Protein synthesis | "Protein factory" |
| Peroxisome | Single | breakdown (catalase) | — |
| Centriole | None | Spindle formation | — |
Structural Proteins
| Structure | Protein |
|---|---|
| Prokaryotic flagella | Flagellin |
| Eukaryotic cilia/flagella | Tubulin (9+2 arrangement) |
| Microfilaments | Actin |
| Intermediate filaments | Keratin, vimentin, desmin (cell-type specific) |
| Middle lamella (plant) | Calcium pectate |
| Bacterial cell wall | Peptidoglycan (murein) |
| Fungal cell wall | Chitin |
| Plant cell wall | Cellulose |