Editing Nutrient sensing (section)

==Nutrient sensing in mammalian cells==

A rapid and efficient response to disturbances in nutrient levels is crucial for the survival of organisms from bacteria to humans. Cells have therefore evolved a host of molecular pathways that can sense nutrient concentrations and quickly regulate gene expression and protein modification to respond to any changes.<ref>Zagorski, Nick. "Nutrient Sensing, Signaling, & Regulation." Journal of Biological Chemistry. (2010): n. page. Web. 9 Apr. 2013. http://www.jbc.org/site/meeting2010/nutrient</ref>

Cell growth is regulated by coordination of both extracellular nutrients and intracellular metabolite concentrations. [[AMP-activated protein kinase|AMP-activated kinase (AMPK)]] and [[MTORC1|mammalian target of rapamycin complex 1]] serve as key molecules that sense cellular energy and nutrients levels, respectively.
*The interplay among nutrients, metabolites, gene expression, and protein modification are involved in the coordination of cell growth with extracellular and intracellular conditions.<ref>Molecular Cell, Volume 49, Issue 3, 379-387, 7 February 2013</ref>

Living cells use [[Adenosine triphosphate|ATP]] as the most important direct energy source. Hydrolysis of ATP to [[Adenosine diphosphate|ADP]] and [[phosphate]] (or [[Adenosine monophosphate|AMP]] and [[pyrophosphate]]) provides energy for most biological processes. The ratio of ATP to ADP and AMP is a barometer of cellular energy status and is therefore tightly monitored by the cell. In eukaryotic cells, AMPK serves as a key cellular energy sensor and a master regulator of metabolism to maintain energy homeostasis.<ref>{{cite journal|author=Yuan, Hai-Xin|title=Nutrient Sensing, Metabolism, and Cell Growth Control|journal= Molecular Cell|year=2013|volume=49|issue=3|pages=379–387|doi=10.1016/j.molcel.2013.01.019|pmid=23395268|pmc=3587157|access-date=2 April 2013|url=http://www.stanford.edu/class/cbio101/coursework/yuan2013.pdf}}</ref>