O Levels Biology (5090)•5090/12/M/J/24
Explanation
Nitrogen in Biomolecules
Steps:
- Recall that food molecules include proteins, lipids, and carbohydrates, each with distinct elemental compositions.
- Proteins are built from amino acids, which contain carbon, hydrogen, oxygen, and nitrogen.
- Lipids consist of fatty acids and glycerol, primarily carbon, hydrogen, and oxygen.
- Carbohydrates like glucose contain only carbon, hydrogen, and oxygen.
Why A is correct:
- Amino acids have the general formula R-CH(NH2)-COOH, where the amine group (NH2) includes nitrogen.
Why the others are wrong:
- B. Fatty acids have the formula R-COOH, lacking nitrogen.
- C. Glucose is a carbohydrate with formula C6H12O6, no nitrogen.
- D. Glycerol has formula C3H8O3, composed of carbon, hydrogen, and oxygen only.
Final answer: A
Topic: Biological molecules
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