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Physics of biological systems – PH 419
LECTURE 16:
Biological dynamics and rate equations
mithun@phy.iitb.ac.in Office: Physics 303
Gene expression during cell cycle of caulobacter
Physics of biological systems PH 419 LECTURE 16: Biological - - PowerPoint PPT Presentation
Physics of biological systems PH 419 LECTURE 16: Biological - - PowerPoint PPT Presentation
Physics of biological systems PH 419 LECTURE 16: Biological dynamics and rate equations mithun@phy.iitb.ac.in Office: Physics 303 CELLS ARE IN CONSTANT FLUX Gene expression during cell cycle of caulobacter The living cytoskeleton Dynamic
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The living cytoskeleton
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Dynamic instability of microtubules
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Dynamic instability of microtubules
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Actin polymerization
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Actin TREADMILLING
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Actin polymerization
Kalman Lab, Emory Cossart Lab, Institut Pasteur
Mechanobio.info
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Actin polymerization
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CHEMICAL REACTIONS
➢Changes in numbers of reacting molecules ➢Changes in time as well as changes in space ➢Concentration, c(r,t) ➢If species numbers are very small, fluctuations can be as important ➢Local vs global concentrations
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RATE EQUATIONS
Assume, no spatial variations
𝑒𝑑𝑗 𝑒𝑢 = 𝑔 𝑑
𝑘}, {𝑙𝑗
= 𝑔 𝑑1,𝑑2,. . . , 𝑑𝑜; 𝑙1,𝑙2,. . . , 𝑙𝑛
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Retinal: Conformational change
𝑒𝑑 𝑒𝑢 = −𝑙𝑑 𝑑 = 𝑑0𝑓
−𝑢 τ τ =
1 𝑙
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The trajectory picture
σ𝑗 𝑢 = 1, if𝑢 < 𝑢𝑗 0, otherwise 𝑞 𝑢 Δ𝑢 = 1 τ 𝑓
−𝑢 τΔ𝑢
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Decay and growth
𝐵 → 𝐶
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Bimolecular reactions
𝐵 + 𝐶 ⇔ 𝐵𝐶
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𝑒𝑞𝑝 𝑒𝑢 = −𝑙+𝑞𝑝 + 𝑙−𝑞𝑑 𝑞𝑝 = 𝑙− 𝑙+ + 𝑙− + 𝑙+ 𝑙+ + 𝑙− 𝑓− 𝑙++𝑙− 𝑢
ION CHANNEL gating
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RAPID EQUILIBRIUM
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ENZYME KINETICS
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