Prepare for NEET Biology Mineral Nutrition with MCQs & PYQs on NEET.GUIDE. Enjoy free practice, previous year questions, and expert solutions to understand nutrient uptake and deficiency.
The enzyme nitrogenase is highly sensitive to oxygen. How do root nodules maintain a low oxygen environment necessary for nitrogen fixation?
Active transport of oxygen out of the nodule
Anaerobic respiration within the bacteroids
Leghemoglobin binds oxygen, buffering its concentration
Thick cell walls of the nodule prevent oxygen diffusion
Which of the following is NOT a direct consequence of Nod factor signaling in the host plant during root nodule formation?
Root hair curling
Formation of infection threads
Cortical cell division leading to nodule primordia formation
Expression of nif genes in bacteroids
Certain mutant legumes exhibit excessive root hair curling in the presence of rhizobia, but infection threads fail to penetrate the cortex. This phenotype is MOST likely due to a defect in:
Flavonoid production by the root
Rhizobial nod gene expression
Nod factor receptor function
Signaling pathway downstream of Nod factor perception, affecting infection thread growth
A researcher isolates a mutant strain of Rhizobium that is unable to synthesize leghemoglobin. Which of the following is the MOST LIKELY consequence of this mutation on nitrogen fixation?
Enhanced nitrogenase activity due to increased oxygen availability
Reduced nitrogenase activity due to oxygen toxicity
No change in nitrogenase activity as leghemoglobin is not directly involved
Increased nitrogen fixation due to higher free oxygen levels
The free energy change () for nitrogen fixation is highly positive. Which of the following BEST explains how biological nitrogen fixation occurs despite this energetic barrier?
The reaction proceeds spontaneously at high temperatures found in root nodules
Nitrogenase acts as a catalyst, lowering the activation energy but not the
Hydrolysis of a large number of ATP molecules coupled to the reaction
The presence of leghemoglobin alters the thermodynamics, making negative
Which intermediate in nitrogen assimilation is directly responsible for the toxic effects of ammonia accumulation in plants?
Ammonia
Glutamine
Glutamate
Carbamoyl phosphate
Nitrifying bacteria play a crucial role in the nitrogen cycle by:
Converting atmospheric nitrogen into ammonia
Reducing nitrate to nitrite and then to nitrogen gas
Oxidizing ammonia to nitrite and then nitrate
Converting organic nitrogen into ammonia
A plant is grown in a hydroponic solution deficient in molybdenum. Which of the following processes related to nitrogen metabolism would be MOST directly affected?
Nitrogenase activity
Nitrate reductase activity
Glutamine synthetase activity
Aminotransferase activity
Which element is NOT essential for the synthesis of chlorophyll?
Magnesium
Nitrogen
Iron
Sodium
