29 March 19

Molybdenum’s Role in Nitrogen Fixing

Molybdenum role has been renowned to many scientists to be one of the most unique nutrients required for the development of life, as its key role in breaking the strongest molecule within the atmosphere, turning the most abundant element within the atmosphere nitrogen gas (78%) to 31st within the crust (0.002%). Why Molybdenum, due to its key role in the mechanism within an organism turning Nitrogen gas (N2) into ammonia (NH3) with a specialized enzyme named Nitrogenase that facilitates breaking this bond through the capabilities of Molybdenum’s elemental characteristics derived from Its overall weight/size that both correlates to how it acts as an element but more importantly in its rarity/deficiency within the soil.

The Limitation…

The weight of the element Molybdenum greatly eclipses those weights of naturally utilised elements, weighing 98 atomic mass units as compared to Phosphorous being 31 and Potassium 39 and the rest of naturally utilised elements having substantially less mass giving Molybdenum the ambiguous title of heaviest element to be frequently found deficient in the soil. The fact of its rarity is suggestive from its corresponding weight and this is known as the rough rule in chemistry that with weight of an element comes more rarity. Interestingly due to this rule and the importance of fixed nitrogen needed for life, the scarcity of Molybdenum in the Earth has resulted into being the limiting factor to nearly 2 billion years of evolution of life (more than 50% of life on earth). These defining limitations of the dependence of life to Molybdenum’s use within Nitrogenase suggests the complexity of the development of this mechanism of converting nitrogen gas to ammonia and later fixed nitrogen which in comparison comes effortlessly for all organisms.

The Complexity…

Molybdenum’s capabilities to facilitate this highly unique and demanding conversion for usable Nitrogen comes with its limitation within organisms or more specially the organisms that have adapted for this limitation/restriction. These organisms are known as Diazotrophs that create anaerobic conditions within heterocyst’s organelles that allow Molybdenum to transition unimpeded through its oxidation states… what does this all mean? Well, the main point from this is the requirement of anaerobic conditions meaning absence of oxygen in a biotic (living) environment which cannot be easily achieved within life therefore the adaptation/development of specialized organisms (Diazotrophs) that have formed unique cell-structures (organelles) that differentiate with multiple walls (heterocyst) the oxygen rich exterior to the anaerobic interior allowing this mechanism to be unimpeded.

The Mechanism…

Oxidation states and “abundance” are the factors that define the importance of Molybdenum into the use within this mechanism, where definition of oxidation states is roughly factored into how much it weighs therefore reaching a point of limited abundance with ideal oxidation states that being Molybdenum. What is oxidation states and its importance… that question becomes very hard to describe needing the understanding of elements that being protons, electrons and pairing of electron shells, so to put it simply (hopefully) oxidation states is the capability of holding and letting go more electricity (electrons), meaning it can store lots of electrons to than transfer to nitrogen gas which results in these specialized conditions to transform it into ammonia then later fixed nitrogen.

Life Finds A Way

Author: Barclay Rohrlach, AgroBest, 2018