the human body blueprint

biologists had pinpointed certain microscopic factors that managed organelle fluctuations. Recent studies have revealed new insights into quantitative concepts emphasizing organelle size control. Organelles grow in random bursts to supply the cell with a widespread biophysical mechanism which then allows it to maintain reliable organelle sizes The list of organelles includes lipid droplets that store fat, and mitochondrias that generate chemical energy

As the size of an organelle strongly affects how molecules circulate across its barrier, eukaryotic cells must accurately regulate the size and number of organelles. To support the theory of organelles growing in random bursts, Shankar Mukherji and his colleagues at Washington University in St Louis constructed a “limiting-pool model” simulation, along with two alternative models to demonstrate how organelles grow by the joining of basic components. In the simulations, organelles could increase in number through the fusion of a new organelle or through the splitting of one or two existing organelles. For each model, a relation was identified between the average size and number of organelles The two alternative models focused on predicting the constant organelle size, while the limiting-pool model focused on predicting how the size should slowly lessen with increasing numbers of organelles. Mukherji and his colleagues then compared these model results with real life measurements of organelles, while using a fluorescent protein to mark the organelle membranes While inspecting the images of three different organelles, it was found that the limiting pool model worked best in predicting the relation between average size and number of organelles. However, with a closer inspection of these models, a disagreement between the theory and their experiment over organelle size variation was revealed In the measurements of the real cells, researchers found that alterations were constant, which was always around 50% of the average organelle size. This result conflicted with the limiting-pool model, which predicted that the correspondent size of variations should be greater in cells with smaller organelles

To account for the inconsistency, the team adjusted the limiting-pool model using inspiration from earlier work Their new model assumed that organelles grow from a pool of building blocks in occasional bursts rather than at a steady rate. With a series of new simulations of the edited model, it was still found that the average size of an organelle decreased with increased numbers, which takes into consideration the limiting-pool growth It was also found that the growth dynamics led to smaller versions in organelle size, also seen in real cells. Therefore, this new model can explain how cells maintain organelle sizes and numbers while also regulating size fluctuations.