Question

Which of the following is not one of the four most common elements found in living organisms?
(a) Hydrogen
(b) Carbon
(c) Sulphur
(d) Nitrogen

Answer 1

Hint: Nutrients are required by living organisms to carry out metabolic reactions in the body. Nutrients are further classified into macronutrients and micronutrients based on the quantity required by the body. The four most common elements of the body are the ones that make up the structure of cells.

Complete Answer:
The four most common elements are oxygen, carbon, hydrogen and nitrogen. Along with calcium and phosphorus, they make up $99\%$ of the mass of living organisms. Sulphur is the element that is not one of the four most common elements. Sulphur belongs to the category of macronutrients and it is absorbed by plants in the form of sulphate ions ${ { SO }_{ 4 } }^{ 2- }$. Sulphur is part of two amino acids known as cysteine and methionine as well as it is the main constituent of many coenzymes, vitamins (thiamine, biotin, coenzyme A) etc.

Additional information: If we consider a human being of mass 80 Kgs, then the most common elements would comprise as follows:
Oxygen: Oxygen will make up to 52 Kg of that human being and is it the most abundant element present in our bodies.
Carbon: Carbon will make up to 14.5 Kg and it is the second most abundant element in the body. It is the structural element of all our compounds and thus we are known as carbon-based life forms.
Hydrogen: Hydrogen will make up 8 Kg and it along with carbon makes up hydrocarbon which makes up our body.
Nitrogen: Nitrogen is very important as well because it is a major constituent of proteins, nucleic acids, vitamins and hormones.
So, the correct option is ‘(c) Sulphur’.

Note: Macronutrients are nutrients that are required in larger amounts such as more than 10 mmole ${ Kg }^{ -1 }$.
Micronutrients are nutrients that are required in smaller amounts such as less than 10 mmole ${ Kg }^{ -1 }$.
Macronutrients and micronutrients together have 17 essential elements.