Minerals and Nutrients

In the human body, the major elements by mass are oxygen (~65%), carbon (~18.5%), hydrogen (~9.5%), and nitrogen (~3.2%). Iron, while essential for hemoglobin and oxygen transport, is a trace element present in only about 0.006% of body mass. Among the given options (oxygen, hydrogen, carbon, iron), iron is present in the smallest quantity.

The magnesium ion required for the activation of RuBisCo is released from the thylakoid lumen when the inner pH drops due to the active pumping of protons from the electron flow.

Nitrogen is required by plants in the largest quantity among these options. It's essential for chlorophyll production, protein synthesis, and overall plant growth. Plants absorb nitrogen primarily as nitrates or ammonium from soil.

The human body is primarily composed of oxygen (about 65%), carbon (about 18.5%), hydrogen (about 9.5%), nitrogen (about 3.2%), calcium (about 1.5%), and phosphorus (about 1.0%). Iron, while essential for hemoglobin, constitutes only about 0.006% of body mass, making it the least abundant among these options.

Oxygen is the most abundant element in the Earth's crust, constituting approximately 46.6% by weight. It's found in silicate minerals, oxides, and water. Silicon is the second most abundant (about 27.7%), followed by aluminum (about 8.1%), and iron (about 5.0%). Carbon, hydrogen, and nitrogen are much less abundant in the crust.

Phosphorus present in an organic compound is estimated by Carius method. A known mass of the organic compound is heated with fuming nitric acid in a Carius tube for about 2 hours when P present in the compound is oxidised to phosphoric acid. It is precipitated as magnesium ammonium phosphate (Mg(NH₄) PO₄) by adding magnesia mixture (MgCl₂, NH₄Cl and a little aqueous NH₃). The precipitate is filtered, washed, dried and then ignited to give magnesium pyrophosphate (Mg₂P₂O₇). It is then weighed. From the masses of organic compound and magnesium pyrophosphate obtained, the percentage of P in the organic compound can be calculated.

Siderophilin has Fe strongly bound by proteins. It is an important metalloprotein and constitutes about 30% of plasma protein. It facilitates iron transport.

Insulin is stored in the pancreas as zinc-insulin hexamer crystals. Zinc ions stabilize insulin's structure and are essential for its storage and release. This trace metal is crucial for insulin's biological activity.

Aconitase is an iron-containing enzyme, catalysing the interonversion of citrate and isocitrate in the citric acid cycle.

Magnesium behaves antagonistically to fluoride absorption. Magnesium competes with fluoride and decreases the absorption of that mineral when taken at the same time. This protects the body from harmful effects of fluorine.

Copper is necessary for iron absorption, and its deficiency can lead to low iron levels.

Phosphorus is important in plant bioenergetics. As a component of ATP, phosphorus is needed for the conversion of light energy to chemical energy (ATP) during photosynthesis. It is a primary macronutrient of the plants.

Iron is essential for forming haemoglobin in the blood.

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