The four elements that together make up about 99 per cent of the mass of living matter are
Correct answer: A. carbon, hydrogen, oxygen and nitrogen
- A. carbon, hydrogen, oxygen and nitrogen
- B. carbon, hydrogen, oxygen and sulphur
- C. sodium, potassium, calcium and chlorine
- D. carbon, nitrogen, phosphorus and sulphur
Explanation
Carbon, hydrogen, oxygen and nitrogen are the backbone of carbohydrates, lipids, proteins and nucleic acids, with phosphorus and sulphur adding roughly another one per cent. Sodium, potassium and calcium are essential but are needed only in small quantities as ions. Carbon is central because it forms four stable covalent bonds and so builds long chains and rings.
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About Classification of Biological Molecules
Biological molecules are classified as carbohydrates, lipids, proteins and nucleic acids, with water, minerals and vitamins also supporting cellular processes. The key distinctions involve their monomers, chemical bonds, structures and functions, including glucose and starch, fatty acids and triglycerides, amino acids and polypeptides, and nucleotides in DNA and RNA.
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