Membrane flow per unit area - 1st Fick's eqn
J = −D∇C
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| Term | Definition |
|---|---|
| Membrane flow per unit area - 1st Fick's eqn | J = −D∇C |
| Membrane evolution of concentration - 2nd Fick's equation | ∂C/∂t = D∇^2C = D∆C |
| single-cell vs multicellular organisms | - single-cell = limited functions - multicellular = specialization and multitasking |
| another example of cellular components that can be measured | - membrane shell mechanics - shear stress - two-dimensional liquid (rearrangement) |
| membrane biaxial tension and area expansion modulus are measured via | area strain equations A = L^2 Ka = Eh/2 (1 − ν) 0.1 − 10 N/m |
| under biaxial tension and/or area expansion modulus the membrane is ____ | effectively inextensible (up to 4-6%) |
| membrane bending stiffness can be measured with | Kb = Eh^3/12*(1 − ν^2) 10^-19 N/m |
| mitochondri | - provide energy to the cell via glucose and oxygen - protein synthesis, division, motility |
| nucleus | - 95% of DNA - stiffest component |
| cilia | - short - hundreds per cell - rotational movement |
| flagella | - long - less than 10 per cell - wave like and sinusoidal movement |
| cytoskeleton composed of | - microfilaments (actin): thinnest, 6 nm diameter - microtubules: hollow cylinders, very dynamic, 10 nm diameter - intermediate filaments: more stable, 20 nm diameter |
| cell migration occurs | - in response to external cues - to find nutriments - positive or negative migration |
| external cues | - chemotaxis - electrotaxis - thermotaxis - phototaxis - positive or negative migration - mechanotaxis - durotaxis - geotaxis |
| an example of electrotaxis is | wound healing |
| an example of thermo and phototaxis is | sperm guidance and plant growth |
| an example of mechanotaxis is | fluid shear stress |
| an example of durotaxis is | stiffness gradient |
| an example of geotaxis is | - microstructured substrates - cellular confinement |
| migration requirements | motility polarity adhesion |
| motility | intrinsic ability to move (motility phenotype) |
| polarity | ability to orient towards an external cue |
| adhesion | ability to adhere to fibers, substrate or neighbors |
| migration steps | 1. protrusion 2. focal adhesion at the front 3. contraction 4. focal adhesion at the back |
| examples of protrusion | - lamellipodia - filipodia - pseudopodia - actin polymerization |
| lamellipodia | projection of frontal edge of the cell |
| filipodia | rodlike, thin protrusions with rounded ends |
| pseudopodia | broad and flat appendages |
| actin polymerization | brownian movement |
| brownian movement | fluctuation of membrane = fluctuation in actin filament |
| brownian fluctuation of membrane | 2 scenarios if the membrane fluctuates leftward = nothing happens. actin is not polymerized if the membrane fluctuates rightward = F-actin is polymerized and extended |
| examples of adhesion | cell-cell cell-matrix cell-substrate focal adhesions |
| cell-cell adhesion | - maintain epithelial tissues - facilitate directed collective migration |
| cellular automata models | - discrete - each point of the lattice occupied or not by the cell - probability of occupation depending on external factors |
| semi-discrete models | - no mesh of the domain, but of the membrane - all points on the membrane are connected to the nucleus by springs - external signals |
| continuum models | - partial differential equations describing mechanical equilibrium - constitutive laws - stress-strain field influencing cell shape |