BIOL 112 Lecture 8: cells
31 Jan 2019
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Cells have a nucleus, microtubules, actin and a cell membrane. Estimation at 4 x 1013 cells (and there is about same number of bacterial cells) Because most chemical (metabolic) reactions in cells require diffusion (or the reactants to encounter each other"s by chance or the enzymes that catalyze the reaction): Diffusing molecules don"t travel long distances because of their random walk . The distance that is traveled by a molecule is proportional to the square root of time: Big molecule (like a protein) travels 10 m in 1s (distance=10 x 1) Example: small cell with a 1 mm side length has a surface area to volume ratio of 6/1 = 6. But a 10 mm cell have a surface area to volume ratio of 600/1000 = 6/10 = 1/1. 7 (it is inverted) There is no diffusion because the egg cell is just a storage device (nothing is going on), as long as it is not fertilized.
