Question

Which one of the following statements is incorrect?

• A. Nitrogen is one of the top five elements found in plants and animals.
• B. Industrial and biological nitrogen fixation require the input of substantial amount of energy.
• C. Nitrogen in organisms is only found in nucleic acids, i.e. DNA and RNA.
• D. Nitrogen is plentiful in the earth's atmosphere in relatively inert forms.

Hint:

Remember the two main biological macromolecules containing nitrogen: Proteins (via amino acids) and Nucleic Acids (via nitrogenous bases). Any statement limiting nitrogen to just one of these is incorrect.

Answer 1

The Correct Option is C

Step 1: Analyze statement A.
The most abundant elements in living organisms are Oxygen, Carbon, Hydrogen, and Nitrogen. It is a key component, making this statement correct.

Step 2: Analyze statement B.
Breaking the strong triple bond in atmospheric nitrogen (N\(_2\)) is an extremely energy-intensive process. Both the industrial Haber-Bosch process and biological nitrogen fixation by bacteria require massive energy inputs. This statement is correct.

Step 3: Analyze statement C.
Nitrogen is a fundamental component of all amino acids, which are the building blocks of proteins. It is also a component of the nitrogenous bases in nucleic acids (DNA and RNA), as well as in other molecules like ATP and chlorophyll. The statement that it is only found in nucleic acids is incorrect.

Step 4: Analyze statement D.
The Earth's atmosphere is approximately 78% nitrogen gas (N\(_2\)). The triple bond in N\(_2\) makes it very stable and chemically inert, so it is not readily available for use by most organisms. This statement is correct. Conclusion: Statement C is the incorrect one.