In human body percentage of which element is highest?

Question

UnlockIAS · Accepted Answer

Correct — D, oxygen. By mass, oxygen makes up about 65% of the human body. This is because the body is roughly two-thirds water (H2O), in which the heavy atom is oxygen, and oxygen is also abundant in proteins, carbohydrates and fats. The usual mass order is Oxygen (~65%) > Carbon (~18%) > Hydrogen (~10%) > Nitrogen (~3%).

Why the other options are wrong — (a) Hydrogen is the most abundant element by NUMBER of atoms (light atoms in water), but because each atom is so light it is only about 10% by mass — the question asks by percentage (mass).  (b) Nitrogen (in proteins and nucleic acids) is only about 3% of body mass — far below oxygen.  (c) Carbon is the backbone of all organic molecules and is second by mass (~18%), but still well below oxygen.

Concept: Almost the entire human body (~96% by mass) is made of just four elements — oxygen, carbon, hydrogen and nitrogen — because it is largely water plus organic macromolecules. Oxygen leads by mass mainly through water and organic compounds.

State PCS 2019 Q84 — Science & Technology PYQ with Answer

State PCS 2019 Q84 — Science & Technology PYQ with Answer