The Question is from neet-botany mineral-nutrition n2-metab0lism, and it was created by the author K SURESH KUMAR

Question

Which intermediate in nitrogen assimilation is directly responsible for the toxic effects of ammonia accumulation in plants?

K SURESH KUMAR · Accepted Answer

## CORE INFORMATION
✓ **Answer**: A
## CONCEPT FRAMEWORK
	**Primary Concept**: Nitrogen assimilation and toxicity in plants
	**Related Topics**: Ammonia detoxification, Glutamine synthetase, Glutamate synthase, Nitrogen cycle
	**Prerequisites**: Basic plant physiology, Nitrogen metabolism
## SOLUTION PATHWAY
**Given Information**:
	The question asks about the direct cause of toxicity from excess nitrogen.
**Method & Steps**:
	1. **Understanding Nitrogen Assimilation**: Plants take up nitrogen, primarily as nitrate ($NO_3^-$), which is then reduced to nitrite ($NO_2^-$) and finally to ammonia ($NH_3$). Ammonia is then incorporated into organic compounds.
	Reasoning: This process is essential for creating amino acids and other nitrogen-containing biomolecules.
	2. **Ammonia Toxicity**: While crucial for amino acid synthesis, free ammonia is highly reactive and can disrupt cellular processes at high concentrations.
	Working:  Ammonia interferes with pH gradients and membrane potential, uncouples photophosphorylation, and inhibits other key enzymes.
	Key Point: The other options represent ways plants detoxify ammonia, not the direct cause of toxicity.
	3. **Detoxification Mechanisms**: Plants have evolved mechanisms to rapidly convert ammonia into less toxic forms, primarily glutamine and glutamate.
	Result: Ammonia itself is the toxic agent.
	Verification: Scientific literature and plant physiology textbooks confirm ammonia's direct toxicity.
## OPTION ANALYSIS
[A] ✓: Ammonia is the directly toxic molecule that accumulates when nitrogen assimilation surpasses detoxification capacity.
[B] :x: Glutamine is a product of ammonia detoxification, formed by the enzyme glutamine synthetase. It is a less toxic storage and transport form of nitrogen.
[C] :x: Glutamate is another product of ammonia detoxification, formed from glutamine by glutamate synthase. It also serves as a precursor for other amino acids.
[D] :x: Carbamoyl phosphate is involved in other nitrogen metabolic pathways, like arginine and pyrimidine biosynthesis, but it's not directly involved in the primary ammonia detoxification pathway related to nitrogen assimilation and is not the primary toxic agent.
## LEARNING AIDS
	**Common Mistakes**:
		1. Confusing ammonia detoxification products with the toxic agent: Remember that glutamine and glutamate are formed *from* ammonia to *reduce* toxicity.
		2. Overlooking the reactivity of ammonia: Its chemical properties make it disruptive to cellular processes at high concentrations.
	**Quick Tips**:
		1.  Think of ammonia as a necessary but potentially harmful intermediate in nitrogen assimilation.
		2. Remember the key enzymes: Glutamine synthetase (GS) and Glutamate synthase (GOGAT) are essential for detoxifying ammonia.

K SURESH KUMAR · Answer

The correct Option is "Ammonia"

K SURESH KUMAR · Answer

Glutamine

K SURESH KUMAR · Answer

Glutamate

K SURESH KUMAR · Answer

Carbamoyl phosphate

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