4. Recognition and self-assembly of macromolecules. Cytoskeleton.
Covers how macromolecules spontaneously assemble into complexes through spatial affinity, shape compatibility, surface charge and non-covalent bonds, then classifies complexes as protein-protein, protein-nucleic acid and protein-lipid. It walks through nucleosomes, sperm chromatin, ribosome and viral assembly, lipoproteins and membrane structure, before moving to the three cytoskeletal filament types: microtubules with their centrioles and ciliary axoneme, actin microfilaments with myosin, and intermediate filaments by tissue type. Short mnemonics for the complex classes and cytoskeletal components close the note.
Topic 5 of 105 in the MU Sofia syllabus for Biology (Medicine, Year 1). The free AceMed note covers it in 15 sections, about 368 words (3 min of reading), with 25 flashcards.
In this note
🧬 Recognition and Self-Assembly of Macromolecules & Cytoskeleton
🔧 Self-Assembly of Macromolecules
📦 Classifications of Complexes
🧩 Protein × Protein Interactions (Quaternary Structures)
🧬 Protein × Nucleic Acid (Nucleoproteins)
🧴 Protein × Lipid (Lipoproteins)
🧱 Cytoskeleton Overview
🌐 Microtubules
🧬 PCD (Primary Ciliary Dyskinesia)
💪 Microfilaments (Actin Filaments)
🧵 Intermediate Filaments
✅ Summary Mnemonics
🧪 Cytoskeletal Components
🧠 Cilia Movement
🧬 Microtubule Motors
🔧 Self-Assembly of Macromolecules
Macromolecules spontaneously assemble into supramolecular complexes based on:
🔵 Spatial affinity
🟣 Shape compatibility
🟢 Surface charge
🟡 Non-covalent interactions:
Ionic bonds
Hydrogen bonds
Van der Waals forces
Hydrophobic forces
📦 Classifications of Complexes
Protein × Protein → Quaternary structures (e.g., Hemoglobin, CDK-Cyclin)
Protein × Nucleic Acid → Nucleoproteins (e.g., Nucleosome)
Protein × Lipid → Lipoproteins (e.g., HDL, LDL)
🧩 Protein × Protein Interactions (Quaternary Structures)
Small complexes: Hemoglobin (2α + 2β)
Large complexes: Cytoskeleton, ECM fibers, viral capsids
Example: Collagen – strong fiber protein
🧬 Protein × Nucleic Acid (Nucleoproteins)
🔹 Nucleosome
DNA wrapped around histone octamer (H2A, H2B, H3, H4)
Diameter: 10 nm
Connected via linker DNA
Basic unit of chromatin
🔹 Sperm Chromatin
Histones replaced by protamines → DNA tightly packed into toroids
🔹 Ribosome Assembly
3 rRNAs + ~50 proteins = functional ribosome
Multi-step: Synthesis → Folding → Binding
🔹 Tobacco Mosaic Virus
Assembly starts with protein disks → RNA enters → Helix formed
