Question

The four elements called "big-four" which make up 95% of all elements found in a living system are
A) C, H, N, O
B) C, H, O, P
C) C, H, O, S
D) C, N, O, P

Answer 1

Hint: The living cell is made up of several types of elements which are categorised as major and minor elements. The major elements are the constituents of carbohydrates, proteins and lipids which are essential for biological functions and build up our body. The major elements are termed as big four elements.

Complete answer:
The living organism is made up of elements which are present as major elements and also in traces. These elements form the framework of our body. The elements which are present in our body are carbon, nitrogen, hydrogen, oxygen, phosphorus, sulphur etc. Out of these 6 major elements, the most important element called the big four elements are C, H, N, O.

Significance of the Big-Four elements-
Carbon- It is the most important element required for the living body. It is the basic component of all forms of biomolecules. It is an important constituent of carbohydrate which is the instant source of energy.
Nitrogen- Nitrogen forms the framework of amino acids, proteins, DNA and RNA. The amino acids and proteins are required for carrying out metabolic processes. Hydrogen- Hydrogen along with carbon is the basic unit of biomolecules.
Oxygen- Oxygen is the only essential element which supports life. With the help of oxygen, organisms are able to break down food which in turn releases energy. The energy produced is in the form of ATP.
Phosphorous- It is the major constituent of bones, teeth, DNA, RNA. ATP or the energy molecule also contains phosphorus. It is essential in metabolic reactions.
Sulphur- It is an important component of certain amino acids. Sulphur plays a vital role in DNA repair, signalling and also in cell division.

Thus the correct answer is option ‘A’.

Note: Our body is made up of carbohydrates, proteins, lipids. The basic composition of this biomolecules are carbon, nitrogen and hydrogen. Oxygen is another important element which is needed by the living beings to carry out respiration.