A physical model of cell metabolism

Cell metabolism is characterized by three fundamental energy demands: to sustain cell maintenance, to trigger aerobic fermentation and to achieve maximum metabolic rate. The transition to aerobic fermentation and the maximum metabolic rate are currently understood based on enzymatic cost constraints. Yet, we are lacking a theory explaining the maintenance energy demand. Here we report a physical model of cell metabolism that explains the origin of these three energy scales. Our key hypothesis is that the maintenance energy demand is rooted on the energy expended by molecular motors to fluidize the cytoplasm and counteract molecular crowding. Using this model and independent parameter estimates we make predictions for the three energy scales that are in quantitative agreement with experimental values. The model also recapitulates the dependencies of cell growth with extracellular osmolarity and temperature. This theory brings together biophysics and cell biology in a tractable model that can be applied to understand key principles of cell metabolism

Teleology, Causation and the Atlas Motif in Plato's Phaedo

In this paper, I propose a new reading of Phaedo 99b6-d2. My main thesis is that in 99c6-9, Socrates does not refer to the teleological αἰτία but to the αἰτία that will be provided by a stronger ‘Atlas’ (99c4-5). This means that the passage offers no evidence that Socrates abandons teleology or modifies his views about it. He acknowledges, instead, that he could not find or learn any αἰτία stronger than the teleological one. This, I suggest, allows an interpretation of the Phaedo in which Socrates offers a consistent account of the αἰτία of generation and destruction

Studies of Inclusive Jet Production in ep Interactions at HERA

Inclusive jet production in neutral and charged current deep inelastic scattering, in photoproduction and the transition region has been studied with the ZEUS and H1 detectors at HERA. The measurements have been compared to next-to-leading-order QCD calculations which are used to make determinations of the strong coupling constant.Comment: 3 pages, 5 figures, Conference Proceedings EPS200