What is the main difference between C3 Plants and C4 Plants?

The main difference between C3 Plants and C4 Plants is based on first co₂ fixation product: C3 Plants — 3-PGA (3-phosphoglyceric acid) — a 3C compound. C4 Plants — OAA (oxaloacetate) — a 4C compound. C3 pathway: CO₂ + RuBP → 2 molecules of 3-PGA (Calvin cycle in mesophyll cells) — NCERT Ch. 13

Which is more important for NEET — C3 Plants or C4 Plants?

Both C3 Plants and C4 Plants are equally important for NEET as NTA tests their comparison directly. This topic falls under Photosynthesis in Higher Plants. Key points to remember: C3 pathway: CO₂ + RuBP → 2 molecules of 3-PGA (Calvin cycle in mesophyll cells) — NCERT Ch. 13. C4 pathway: CO₂ + PEP → OAA in mesophyll → malate → transported to bundle sheath → CO₂ released → enters Calvin cycle. Photorespiration is a wasteful process in C3 plants — RuBisCO binds O₂ instead of CO₂.

Difference Between C3 Plants and C4 Plants — NEET Biology

The main difference between C3 and C4 plants is that C3 plants fix CO₂ into a 3-carbon compound (3-PGA) using RuBisCO, while C4 plants first fix CO₂ into a 4-carbon compound (OAA) using PEPcase and have Kranz anatomy. This is a high-yield NEET topic, with NTA testing the first stable product, photorespiration differences, and enzyme specificity.

Comparison Table: C3 Plants vs C4 Plants

Basis	C3 Plants	C4 Plants
First CO₂ fixation product	3-PGA (3-phosphoglyceric acid) — a 3C compound	OAA (oxaloacetate) — a 4C compound
CO₂ acceptor	RuBP (ribulose bisphosphate)	PEP (phosphoenolpyruvate) in mesophyll cells
Key enzyme	RuBisCO (in mesophyll cells)	PEPcase in mesophyll; RuBisCO in bundle sheath cells
Kranz anatomy	Absent	Present — distinct bundle sheath cells around vascular bundles
Photorespiration	High — RuBisCO has oxygenase activity	Negligible — CO₂ concentrated in bundle sheath cells
CO₂ compensation point	High (25–100 ppm)	Low (0–10 ppm)
Optimum temperature	20–25°C	30–40°C
Water use efficiency	Lower	Higher — stomata open for less time
Calvin cycle location	Mesophyll cells	Bundle sheath cells only
Examples	Rice, wheat, soybean, most trees	Sugarcane, maize, sorghum, Amaranthus

Key Points to Remember

C3 pathway: CO₂ + RuBP → 2 molecules of 3-PGA (Calvin cycle in mesophyll cells) — NCERT Ch. 13
C4 pathway: CO₂ + PEP → OAA in mesophyll → malate → transported to bundle sheath → CO₂ released → enters Calvin cycle
Photorespiration is a wasteful process in C3 plants — RuBisCO binds O₂ instead of CO₂
C4 plants have Kranz anatomy — large, agranal bundle sheath cells with thick walls
RuBisCO is the most abundant enzyme on Earth — present in both C3 and C4 plants

NEET Exam Tip

How NTA Tests ThisTop NEET question format: 'Which of the following is NOT a C4 plant?' — memorize that rice, wheat, and potato are C3. Also: 'Where does Calvin cycle occur in C4 plants?' — bundle sheath cells (NOT mesophyll). Assertion-reason on photorespiration is common: 'C4 plants show no photorespiration because PEPcase has no oxygenase activity' — both true, reason explains assertion.

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Difference Between C3 Plants and C4 Plants — NEET Biology

Comparison Table: C3 Plants vs C4 Plants

Key Points to Remember

NEET Exam Tip

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Photosynthesis in Higher Plants — PYQs

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