Cell Division & Cell Cycle
โญ Essential Cytogenetics Distinction
6 Parameters
Mitosis vs Meiosis I vs Meiosis II
Definitive comparative matrix of chromosomal behavior, recombination, kinetochore orientation, and ploidy outcomes across eukaryotic nuclear divisions.
| Feature | Mitosis | Meiosis I | Meiosis II |
|---|---|---|---|
| Biological Purpose | Growth, tissue repair, asexual reproduction | Reductional division, genetic diversity | Equational segregation of sister chromatids |
| Synapsis & Chiasmata Formation | Absent | Present (Zygotene/Pachytene of Prophase I) | Absent |
| Homologous Chromosome Pairing | No pairing; chromosomes align individually | Bivalents/tetrads align at Metaphase plate | No pairing; sister chromatids align individually |
| Metaphase Alignment | Individual chromosomes along equatorial plate | Homologous pairs align double-ranked at equator | Individual chromosomes align along equator |
| Anaphase Segregation Event | Sister chromatids separate (centromeres split) | Homologous pairs separate (centromeres DO NOT split) | Sister chromatids separate (centromeres split) |
| Final Ploidy & Daughter Cells | 2 Diploid (2n) genetically identical cells | 2 Haploid (1n, duplicated 2C) cells | 4 Haploid (1n, single-copy 1C) recombinant gametes |
Ploidy & Centromere Splitting
Mitosis
Centromeres Split: Yes (Anaphase)
Crossing Over: No
Outcome: 2n โ 2n (Identical)
Meiosis I
Centromeres Split: No (Anaphase I)
Crossing Over: Yes (Pachytene)
Outcome: 2n โ 1n (Reduction)
Meiosis II
Centromeres Split: Yes (Anaphase II)
Crossing Over: No
Outcome: 1n โ 1n (Equational)
Cytoskeleton & Motility
โญ Structural Cell Biology Benchmark
7 Parameters
Cytoskeleton: Microfilaments vs Intermediate Filaments vs Microtubules
Comparative diameter, protein subunits, structural polarity, nucleotide binding, and motor protein associations across cytoskeletal classes.
| Property | Microfilaments (Actin) | Intermediate Filaments (IF) | Microtubules |
|---|---|---|---|
| Diameter | ~7 nm (Thinnest) | ~10 nm (Intermediate) | ~25 nm outer, 15 nm lumen (Thickest) |
| Protein Monomer Subunits | G-actin (globular actin polymerizing to F-actin) | Heterogeneous (Keratins, Vimentin, Desmin, Lamin, Neurofilaments) | ฮฑ-tubulin and ฮฒ-tubulin heterodimers |
| Structural Polarity (+/- ends) | Polar (+ barbed end, - pointed end) | Non-polar (apolar antiparallel tetramers) | Polar (+ fast growing ฮฒ, - centrosome-anchored ฮฑ) |
| Nucleotide Triphosphate Bound | ATP (hydrolyzed to ADP during treadmilling) | None required (purely mechanical assembly) | GTP (GTP cap stabilizes, GDP promotes catastrophe) |
| Motor Proteins Associated | Myosins (Myosin I, II, V) | None (no known motor proteins) | Kinesins (plus-end directed) & Dyneins (minus-end directed) |
| Dynamic Instability / Treadmilling | Prominent treadmilling at steady state | Stable rope-like tensile elements; little treadmilling | Dynamic instability (alternating rescue and catastrophe) |
| Specific Inhibitors / Toxins | Cytochalasin (blocks + end), Phalloidin (freezes F-actin) | Acrylamide (disrupts neurofilaments) | Colchicine, Nocodazole, Paclitaxel (Taxol: stabilizes) |
Diameter & Motor Association
Microfilaments
Diameter: 7 nm
Nucleotide: ATP
Motors: Myosins
Intermediate Filaments
Diameter: 10 nm
Nucleotide: None
Motors: None
Microtubules
Diameter: 25 nm
Nucleotide: GTP
Motors: Kinesin / Dynein
Cell Death Pathways
โญ Pathology & Oncology High-Yield
6 Parameters
Cell Death: Apoptosis vs Necrosis vs Autophagy
Morphological, biochemical, and immunological comparison of programmed and unprogrammed cell death mechanisms.
| Feature | Apoptosis (Type I PCD) | Necrosis (Unregulated) | Autophagy (Type II PCD) |
|---|---|---|---|
| Physiological vs Pathological | Physiological & programmed (development, turnover) | Always pathological (severe acute trauma, ischemia) | Adaptive survival during starvation, or fatal self-clearance |
| Cell Volume & Plasma Membrane | Cell shrinkage; membrane blebbing intact | Cellular swelling, oncosis; membrane lysis & rupture | Cytoplasmic vacuolation; intact outer membrane |
| Inflammatory Response | None (apoptotic bodies engulfed quietly by phagocytes) | Severe acute inflammation (DAMPs and cellular leakage) | Generally anti-inflammatory or non-inflammatory |
| Energy (ATP) Requirement | Active process (ATP-dependent caspase activation) | Passive process (ATP depletion triggers lysis) | Active process (ATP-dependent autophagosome formation) |
| DNA Fragmentation Pattern | Internucleosomal 180-200 bp laddering (CAD nuclease) | Random, smeared non-specific enzymatic lysis | Partial degradation within lysosomes |
| Key Molecular Executioners | Caspase cascade (Caspases 3, 7, 8, 9), Cytochrome c | Calpains, cathepsins, reactive oxygen species (ROS) | Atg proteins, LC3-II (lipidated LC3), Beclin-1 |
Inflammation & Energy Profile
Apoptosis
Atp Required: Yes
Inflammation: None
Dna Pattern: Internucleosomal Ladder
Necrosis
Atp Required: No
Inflammation: Severe
Dna Pattern: Random Smear
Autophagy
Atp Required: Yes
Inflammation: Minimal
Dna Pattern: Lysosomal Cleavage
Membrane Transport & Junctions
โญ Foundational Biology Benchmark
6 Parameters
Prokaryotic vs Eukaryotic Cells (Ultrastructural Matrix)
Comprehensive comparative matrix covering genomic organization, organellar compartmentalization, ribosomes, flagellar motors, and division modes.
| Ultrastructural Feature | Prokaryotes (Bacteria / Archaea) | Eukaryotes (Protists, Fungi, Plants, Animals) |
|---|---|---|
| Nuclear Architecture | No true nucleus; naked DNA in non-membrane nucleoid | True double-membraned nucleus with nuclear pore complexes |
| Genome Structure & Histones | Single circular DNA; no true histones (polyamines & HU proteins in bacteria) | Multiple linear chromosomes packaged around octameric histone cores |
| Ribosomal Subunits | 70S (50S large subunit: 23S+5S rRNA; 30S small subunit: 16S rRNA) | 80S cytosolic (60S: 28S+5.8S+5S; 40S: 18S rRNA); 70S in organelles |
| Membrane-Bound Organelles | Completely absent (no ER, Golgi, lysosomes, peroxisomes, mitochondria) | Present (extensive endomembrane system, mitochondria, chloroplasts) |
| Coupled Transcription-Translation | Occurs concurrently in the same cytoplasmic space | Uncoupled: Transcription inside nucleus, Translation in cytoplasm |
| Locomotory Apparatus | Submicroscopic rotary flagellin filament driven by proton motive force | Complex 9+2 axoneme arrangement of microtubules driven by dynein/ATP |
Ribosome & DNA Topology
Prokaryotes
Ribosomes: 70S (50S+30S)
Dna Form: Circular Naked
Transcription Coupling: Coupled
Eukaryotes
Ribosomes: 80S (60S+40S)
Dna Form: Linear Chromatin
Transcription Coupling: Uncoupled
