∞ generated and posted on 2016.08.24 ∞
Chemical substance that organisms need but cannot synthesize on their own.
All organisms require nutrients of various sorts, though those organisms that consume other organisms for their carbon and/or energy – carbon source and energy source, respectively – the major nutrients are energy-rich carbon-containing molecules such as carbohydrates and lipids as well as proteins.
All nutrients must have some means by which they cross lipid bilayers because they must enter cells. Since most nutrients are polar substances, passage into cells requires specific transport proteins to effect such movement.