Month: September 2022

THE ISSUE OF PURPOSE. “Although living systems obey the laws of physics and chemistry, the notion of function or purpose differentiates biology from other natural sciences. Organisms exist to reproduce, whereas, outside religious belief, rocks and stars have no purpose.” https://www.nature.com/articles/35011540 View in LinkedIn

BYZANTINE SYSTEM. “Cells exist far from thermal equilibrium by harvesting energy from their environment. They are composed of thousands of different types of molecule. They contain information for their survival and reproduction, in the form of their DNA. Their interactions with the environment depend in a byzantine fashion on this information, and the information and the machinery that interprets it are replicated by reproducing the cell.” https://www.nature.com/articles/35011540 View in LinkedIn

COOPERATIVE EFFECTS. “Most biological functions arise from interactions among many components. For example, in the signal transduction system in yeast that converts the detection of a pheromone into the act of mating, there is no single protein responsible for amplifying the input signal provided by the pheromone molecule.” https://www.nature.com/articles/35011540 View in LinkedIn

FAILURE OF REDUCTIONISM. “We argue here for the recognition of functional ‘modules’ as a critical level of biological organization. Modules are composed of many types of molecule. They have discrete functions that arise from interactions among their components (proteins, DNA, RNA and small molecules), but these functions cannot easily be predicted by studying the properties of the isolated components.” https://www.nature.com/articles/35011540 View in LinkedIn

INTERACTIONS. “Modules can be insulated from or connected to each other. Insulation allows the cell to carry out many diverse reactions without cross-talk that would harm the cell, whereas connectivity allows one function to influence another. The higher-level properties of cells, such as their ability to integrate information from multiple sources, will be described by the pattern of connections among their functional modules.” https://www.nature.com/articles/35011540 View in LinkedIn

VALIDITY OF MODULES. “Some modules, such as those for protein synthesis, DNA replication, glycolysis, and even parts of the mitotic spindle (the cellular machinery that ensures the correct distribution of chromosomes at cell division), have been successfully reconstituted in vitro. Others are intrinsically more difficult to reconstruct from purified components and, for these, other methods have established the validity of the module.” https://www.nature.com/articles/35011540 View in LinkedIn

MODULAR HIERARCHIES. “The function of a module can be quantitatively regulated, or switched between qualitatively different functions, by chemical signals from other modules. Higher-level functions can be built by connecting modules together.” https://www.nature.com/articles/35011540 View in LinkedIn

THE MANY INPUTS PROBLEM. “One must also ask how a cell integrates information and instructions that come from the many different modules that monitor its internal and external environment. Neurobiology has an analogous problem, where the central nervous system integrates information from different senses and dictates the organism's behaviour.” https://www.nature.com/articles/35011540 View in LinkedIn

MASTER MODULE ISSUE. “Does cellular integration merely emerge from a web of pairwise connections between different sensory modules, or are there specific modules that act as a cellular equivalent of the central nervous system — integrating information and resolving conflicts?” https://www.nature.com/articles/35011540 View in LinkedIn

STABILITY WITH FLEXIBILITY. “Modular structures may facilitate evolutionary change. Embedding particular functions in discrete modules allows the core function of a module to be robust to change, but allows for changes in the properties and functions of a cell (its phenotype) by altering the connections between different modules.” https://www.nature.com/articles/35011540 View in LinkedIn