27/06/2026
MDCAT-2026 Most important key points that every candidate should know for entry test
1. Microvilli increase surface area, NOT motility.
2. Cilia have 9+2 microtubule arrangement and are motile.
3. Stereocilia are modified microvilli (inner ear).
4. Nucleolus is the site of rRNA synthesis (no membrane).
5. Mitochondrial cristae increase surface area for ATP synthase.
6. Smooth ER is abundant in steroid-secreting cells (Leydig cells).
7. Rough ER has ribosomes → synthesizes secretory proteins.
8. Golgi apparatus modifies, sorts, and packages proteins.
9. Lysosomes contain acid hydrolases; primary = inactive, secondary = active.
10. Peroxisomes perform β-oxidation of fatty acids and detoxify H₂O₂.
11. Free ribosomes make cytosolic proteins; bound ribosomes make membrane/secretory proteins.
12. Tight junctions seal epithelial layers (prevent paracellular leak).
13. Desmosomes provide mechanical strength (link intermediate filaments).
14. Gap junctions allow intercellular communication (ions & small molecules).
15. Hemidesmosomes anchor cells to basement membrane.
16. Nuclear pores regulate transport of mRNA and proteins (bidirectional).
17. Euchromatin = active (transcription); heterochromatin = inactive (condensed).
18. Cell cycle: G₁ (growth), S (DNA replication), G₂ (prep), M (mitosis).
19. Mitosis → 2 diploid cells; Meiosis → 4 haploid cells (gametes).
20. Membrane receptors: GPCR, RTK; intracellular receptors: steroid hormones.
21. Second messengers: cAMP, cGMP, IP₃, Ca²⁺.
22. Mitochondria have maternal inheritance (mtDNA).
23. Lipofuscin = "wear-and-tear" aging pigment (non-degradable).
24. Glycogen and lipid droplets are cell inclusions (no membrane).
25. Peroxisomes self-replicate (not from Golgi/ER).
26. Fluid mosaic model describes cell membrane (Singer-Nicolson).
27. Membrane lipids: phospholipids, cholesterol, glycolipids.
28. Integral proteins = transmembrane; peripheral = loosely attached.
29. Glycocalyx = carbohydrate coat for cell recognition.
30. Passive transport: diffusion, osmosis, facilitated diffusion.
31. Active transport: pumps (e.g., Na⁺/K⁺ ATPase), endocytosis, exocytosis.
32. Cytoskeleton: microtubules (25 nm), microfilaments (7 nm), intermediate filaments (10 nm).
33. Microtubules = tubulin; form cilia, flagella, mitotic spindle.
34. Microfilaments = actin; involved in muscle contraction, microvilli.
35. Intermediate filaments = keratin, vimentin, desmin; structural support.
36. Nuclear envelope = double membrane with pores.
37. Nucleoplasm contains chromatin and nucleolus.
38. Smooth ER also stores Ca²⁺ in skeletal muscle (sarcoplasmic reticulum).
39. Rough ER performs N-linked glycosylation of proteins.
40. Golgi: cis (receiving) → medial → trans (shipping).
41. Golgi also adds sugars (glycosylation) and sulfates (sulfation).
42. Lysosomal enzymes are tagged with mannose-6-phosphate (M6P) in Golgi.
43. Lysosomes are involved in autophagy (self) and heterophagy (foreign).
44. Lysosomal storage diseases = enzyme deficiency (e.g., Tay-Sachs).
45. Peroxisomal disorders = Zellweger syndrome (failure to import enzymes).
46. Mitochondrial inner membrane is impermeable; outer is permeable via porins.
47. Mitochondrial matrix contains Krebs cycle enzymes.
48. ATP synthesis occurs via oxidative phosphorylation (OXPHOS).
49. Ribosomes are 80S in eukaryotes (60S + 40S subunits).
50. 70S ribosomes in prokaryotes (50S + 30S) — not in human cells.
51. Translation occurs on ribosomes (mRNA → polypeptide).
52. Cell inclusions: glycogen, lipid, melanin, lipofuscin.
53. Melanin = pigment in skin, hair, retina.
54. Lipofuscin accumulates in aging neurons and cardiac muscle.
55. Tight junctions = zonula occludens; seal intercellular spaces.
56. Desmosomes = macula adherens; link cells via cadherins.
57. Gap junctions = nexus; allow passage of ions up to 1.5–2 nm.
58. Hemidesmosomes attach to basement membrane via integrins.
59. Interphase = G₁, S, G₂ (DNA replication in S phase).
60. Mitosis: prophase → metaphase → anaphase → telophase.
61. Cytokinesis = division of cytoplasm (after telophase).
62. Meiosis I = reductional division (homologous chromosomes separate).
63. Meiosis II = equational division (sister chromatids separate).
64. Crossing over occurs in prophase I of meiosis (genetic variation).
65. GPCR = G protein-coupled receptors (7-transmembrane).
66. RTK = receptor tyrosine kinases (growth factor receptors).
67. Steroid hormones bind intracellular receptors (e.g., cortisol, testosterone).
68. cAMP pathway: activated by Gs; inhibited by Gi.
69. IP₃ pathway releases Ca²⁺ from ER.
70. Ca²⁺ acts as a second messenger in muscle contraction.
71. Cell signaling involves ligand → receptor → cascade → response.
72. Phosphorylation is a common mechanism for signal amplification.
73. Cytosol = site of glycolysis and protein synthesis.
74. Glycosylation occurs in ER and Golgi.
75. Proteolytic cleavage of proteins occurs in Golgi and lysosomes.
76. Autophagosomes engulf damaged organelles → fuse with lysosomes.
77. Phagocytosis = ingestion of large particles (e.g., bacteria).
78. Pinocytosis = ingestion of fluids (small vesicles).
79. Receptor-mediated endocytosis = specific uptake (e.g., LDL via clathrin).
80. Exocytosis = secretion of vesicles (e.g., neurotransmitters, hormones).
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