The Question is from neet-botany photosynthesis-in-higher-plants , and it was created by the author Mr. NARESH KUMAR K

Question

PEP carboxylase
I. is involved in atleast some $C{O_2}$ fixation in both ${C_3}$ and ${C_4} - $ plants
II. Catalyses the reaction of fixing $C{O_2}$ into pyruvic acid in bundle sheath cells
III. is capable of fixing $C{O_2}$ more efficiently at lower atmospheric $C{O_2}$ concentration than RuBP carboxylase
Select the correct option

Mr. NARESH KUMAR K · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
	**Primary Concept**: Photosynthesis (${C_3}$ and ${C_4}$ pathways)
	**Related Topics**: Carbon fixation, RuBisCO, PEP carboxylase, Photorespiration
	**Prerequisites**: Basic understanding of plant physiology and biochemistry.
## SOLUTION PATHWAY
**Given Information**:
	Statements about PEP carboxylase and its role in carbon fixation.
**Method & Steps**:
	1. **Analyze Statement I**: PEP carboxylase is involved in $C{O_2}$ fixation in both ${C_3}$ and ${C_4}$ plants. In ${C_4}$ plants, it is the primary carboxylase, while in ${C_3}$ plants, it plays a role in other metabolic processes, including $C{O_2}$ fixation in some cases.
		Reasoning: This statement is true.
	2. **Analyze Statement II**: PEP carboxylase fixes $C{O_2}$ into oxaloacetic acid (OAA), a four-carbon compound, not pyruvic acid (a three-carbon compound). This occurs in the mesophyll cells of ${C_4}$ plants, not bundle sheath cells.
		Working: PEP + $C{O_2}$ → OAA
		Key Point: The product is OAA, and the location is mesophyll cells.
	3. **Analyze Statement III**: PEP carboxylase has a higher affinity for $C{O_2}$ than RuBisCO and doesn't suffer from photorespiration, making it more efficient at lower $C{O_2}$ concentrations.
		Result: This statement is true.
		Verification: This is a key difference between ${C_3}$ and ${C_4}$ plants.
## OPTION ANALYSIS
[A] :x: Statement II is incorrect.
[B] ✓: Statements I and III are correct.
[C] :x: Statement II is incorrect.
[D] :x: Statement II is incorrect.
## LEARNING AIDS
	**Common Mistakes**:
		1. Confusing the products of PEP carboxylase and RuBisCO: PEP carboxylase produces OAA, while RuBisCO produces a six-carbon unstable compound that quickly breaks down into two molecules of 3-PGA.
			How to avoid: Remember 'P' for PEP and 'O' for OAA.
		2. Confusing the location of PEP carboxylase activity in ${C_4}$ plants: It occurs in mesophyll cells, not bundle sheath cells.
			How to avoid: Remember 'M' for Mesophyll and 'PEP'.
	**Quick Tips**:
		1. PEP carboxylase is key for ${C_4}$ photosynthesis and helps minimize photorespiration.
		2. RuBisCO is the primary carboxylase in ${C_3}$ photosynthesis and is susceptible to photorespiration.

Mr. NARESH KUMAR K · Answer

I and II

Mr. NARESH KUMAR K · Answer

The correct Option is "I and III"

Mr. NARESH KUMAR K · Answer

II and III

Mr. NARESH KUMAR K · Answer

I, II and III

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