细胞生物.7 | Cytoskeleton
Microfilaments vs. Microtubules – Full Bilingual Comparison + Microvilli & Cilia
| Feature | Microfilaments (Actin Filaments) | Microtubules |
|---|---|---|
| Basic unit | G-actin monomer (球状肌动蛋白单体) | α/β-tubulin heterodimer (α/β 微管蛋白二聚体) |
| Structure | Two twisted protofilaments forming a thin flexible helix 双股螺旋，柔软细丝结构 | Hollow tube of 13 protofilaments 13 条原丝围成的中空管状结构 |
| Diameter | ~7 nm | ~25 nm |
| Polarity | Yes: barbed (+) and pointed (−) ends 有极性：快端与慢端 | Yes: plus (+) and minus (−) ends 同样具有极性 |
| Nucleotide used | ATP | GTP |
| Hydrolysis | Actin hydrolyzes ATP → ADP (自身水解 ATP) | Only β-tubulin hydrolyzes GTP → GDP (β 微管蛋白水解 GTP) |
| Assembly dynamics | Treadmilling: polymerize at +, depolymerize at − 像跑步机一样：前面加，后面掉 | Dynamic instability: GTP cap controls growth/shrink 突变性行为：GTP帽调节生长与收缩 |
| Nucleation site | Near membrane; no clear MTOC 靠近膜聚合；无明确中心 | MTOC/centrosome via γ-tubulin ring 中心体起始，由 γ-微管蛋白控制 |
| Associated motors | Myosin (moves toward + end) 肌球蛋白，短距离运输 | Kinesin (+ end), Dynein (− end) 驱动蛋白，长距离运输 |
| Functions | - Cell shape & cortex tension - Cell crawling (lamellipodia, filopodia) - Cytokinesis (contractile ring) - Microvilli support 🦠 Microvilli: • Shape: short, dense, finger-like • Function: increase surface area for absorption (esp. intestines) 细胞形状、皮层张力、细胞爬行、胞质分裂、支持微绒毛 🔍 微绒毛：短小致密，指状；功能是扩大吸收面积，常见于小肠等部位 | - Organelle transport & positioning - Mitotic spindle/chromosome movement - Cilia and flagella movement (axoneme) 🧹 Cilia: • Shape: longer, fewer, motile • Function: move fluid/mucus across surface (e.g. trachea) 长距离运输、纺锤体、染色体分离、纤毛/鞭毛运动 🔍 纤毛：较长，有节律摆动，少量但可动；功能是推动黏液或液体流动，常见于呼吸道 |
| Stability factors | Regulated by ABPs (e.g. formin, cofilin) 肌动蛋白结合蛋白调控 | Regulated by MAPs (e.g. Tau, +TIPs) 微管结合蛋白调控 |
| Disruption drugs | Cytochalasin, Latrunculin 抑制聚合或诱导解聚 | Taxol, Colchicine, Vinblastine 抑制聚合或稳定微管，常用于抗癌 |