🔬 Cell: The Unit of Life (Sizes, Shapes & Structures)
| Category | NCERT Examples | Key Data / Exception |
|---|---|---|
| Smallest Cell | Mycoplasma | 0.3 µm in length (lacks cell wall) |
| Largest Isolated Single Cell | Egg of an Ostrich | Macroscopic cell |
| Human Red Blood Cells (RBCs) | Circular and biconcave | About 7.0 µm in diameter |
| Longest Cells | Nerve cells (Neurons) | Branched and long |
| Bacteria Size | Typical bacteria | 1 to 2 µm (Mycoplasma is smaller) |
| Organelle Sizes | Chloroplast, Mitochondria | Chloroplast: 2-4 µm (w), 5-10 µm (l) Mitochondria: 0.2-1.0 µm (diameter) |
| Inclusion Bodies | Phosphate granules, Cyanophycean granules, Glyco_gen granules | Non-membrane bound storage in prokaryotes |
| Gas Vacuoles | Blue-green, Purple, and Green photosynthetic bacteria | Found in aquatic prokaryotes for buoyancy |
| Cilia & Flagella Arrangement | Eukaryotic core (Axonema) | 9 + 2 arrangement of microtubules |
| Centriole Arrangement | Centrosome core | 9 + 0 arrangement (triplet peripheral fibrils) |
| Chromosomes (Centromere position) | Metacentric, Sub-metacentric, Acrocentric, Telocentric | Telocentric: Terminal centromere (i-shaped) |
🧪 Biomolecules (Chemical Composition & Metabolites)
| Category | NCERT Examples | Key Significance / Sub-types |
|---|---|---|
| Biomacromolecules | Proteins, Nucleic acids, Polysaccharides | Molecular weight > 10,000 Daltons (except Lipids) |
| Acid-Soluble Pool Exception | Lipids | Molecular weight < 800 Da but forms vesicles |
| Most Abundant Protein | RUBISCO (Biosphere), Collagen (Animal world) | Crucial for photosynthesis / Intercellular ground substance |
| Pigments | Carotenoids, Anthocyanins | Secondary metabolites |
| Alkaloids | Morphine, Codeine | Secondary metabolites |
| Terpenoids | Monoterpenes, Diterpenes | Secondary metabolites |
| Essential Oils | Lemon grass oil | Secondary metabolites |
| Toxins | Abrin, Ricin | Secondary metabolites |
| Lectins | Concanavalin A | Secondary metabolites |
| Drugs | Vinblastine, Curcumin | Secondary metabolites (Anti-cancer / Anti-inflammatory) |
| Polymeric Substances | Rubber, Gums, Cellulose | Secondary metabolites |
| Homopolysaccharides | Cellulose, Starch, Glycogen, Inulin | Inulin is a polymer of fructose |
| Heteropolysaccharides | Chitin | Polymer of N-acetyl glucosamine (Exoskeleton of arthropods) |
🔄 Cell Cycle & Cell Division (Duration & Specific Phases)
| Category | NCERT Examples / Phases | Key Timing / Feature |
|---|---|---|
| Human Cell Cycle Duration | 24 Hours | Interphase lasts for 95% of the duration (~23 hours) |
| Yeast Cell Cycle Duration | 90 Minutes | Rapidly dividing eukaryotic cell |
| Quiescent Stage (\(G_{0}\)) | Heart cells, adult animal nerve cells | Metabolically active but no longer proliferating |
| Mitosis in Animals | Diploid somatic cells | Exception: Male social insects (drones) have haploid mitosis |
| Mitosis in Plants | Both Haploid and Diploid cells | Seen in bryophytes, pteridophytes, etc. |
| Leptotene Stage | Chromosomes become gradually visible | First stage of Prophase-I |
| Zygotene Stage | Synapsis of homologous chromosomes | Forms Synaptonemal complex |
| Pachytene Stage | Crossing over, Recombination nodules | Mediated by the enzyme Recombinase |
| Diplotene Stage | Dissolution of synaptonemal complex | Chiasmata formation (lasts months/years in oocytes) |
| Diakinesis Stage | Terminalisation of chiasmata | Nucleolus disappears, nuclear envelope breaks down |