Ques. 1AIPMT 2012 (Prelims)
Which one of the following is wrong statement?
- Anabaena and Nostoc are capable of fixing nitrogen in free-living state also.
- Root nodule forming nitrogen fixers live as aerobes under free-living conditions.
- Phosphorus is a constituent of cell membranes, certain nucleic acids and all proteins.
- Nitrosomonas and Nitrobacter are chemo-autotrophs.
Answer
(3) Phosphorus is a constituent of cell membranes, certain nucleic acids and all proteins.
Solution
Anabaena and Nostoc are free-living cyanobacteria that fix nitrogen, so this is correct.
As per NCERT, Rhizobium (root nodule former) lives as an aerobe under free-living conditions, so this is also correct.
Nitrosomonas and Nitrobacter get energy by oxidising ammonia / nitrite, so they are chemoautotrophs; correct.
As per NCERT, however, phosphorus is a constituent of cell membranes, certain proteins, all nucleic acids and nucleotides.
∴ Statement (3), which says “certain nucleic acids and all proteins”, is wrong.
Answer: (3)