What is the primary reason that plants and animals require nitrogen?

• A. To synthesize proteins and nucleic acids
• B. To form cell membranes from nitrogen-rich lipids
• C. To produce glucose during photosynthesis
• D. To generate ATP directly from nitrogen gas

Answer: (A)

Verified step by step guidance

1. Understand the role of nitrogen in biological systems: Nitrogen is a key element required for the synthesis of essential biomolecules such as proteins and nucleic acids. Proteins are made up of amino acids, which contain nitrogen, and nucleic acids (DNA and RNA) have nitrogenous bases.
2. Eliminate incorrect options: Nitrogen is not directly involved in forming cell membranes, as lipids do not typically contain nitrogen. Similarly, nitrogen is not used to produce glucose during photosynthesis, as glucose synthesis primarily involves carbon, hydrogen, and oxygen.
3. Clarify the role of nitrogen in ATP production: Nitrogen gas (N₂) is not directly used to generate ATP. ATP is synthesized through cellular respiration or photosynthesis, processes that do not involve nitrogen gas directly.
4. Focus on the correct biological function: Nitrogen is essential for synthesizing proteins and nucleic acids, which are fundamental for cell structure, function, and genetic information.
5. Conclude with the correct answer: The primary reason plants and animals require nitrogen is to synthesize proteins and nucleic acids, as these molecules are vital for growth, repair, and reproduction.