C3 And C4 Pathways - Steps, Differences And FAQ

What Is Photosynthesis?

Photosynthesis is the process through which plants convert light energy to chemical energy in the form of glucose. This can happen through different pathways, mainly the C3 and C4 pathways. Knowing what makes the two different plays a key role in the NEET exam, as these adaptations by plants to different environmental conditions are brought out. difference between C3 and C4 Plants

C3 and C4 plants are fundamentally very different in photosynthetic pathways, adaptations, and environmental preferences. Differences between C3 and C4 Plants are explained herein in detail.

What Are C3 and C4 Plants?

The C3 and C4 plants are described below:

C3 Plants

• These plants perform photosynthesis via the Calvin cycle/

• The first stable product is 3-phosphoglycerate (3-PGA), a 3-carbon compound.

• Occur mainly in cool, moist environments.

• Example: Wheat, rice, potato, soybean, barley

C4 Plants

• These plants follow the Hatch-Slack pathway (C4 cycle) before the Calvin cycle.

• The first stable product is oxaloacetic acid (OAA), a 4-carbon compound.

• Occur in hot, dry environments.

• Example: Maize, sugarcane

Major Differences Between C3 and C4 Plants

The major difference between C3 and C4 plants include:

Kranz Anatomy in C4 Plants

In leaves of C4 plants, each vascular bundle or rib is enclosed with a bundle sheath composed of larger parenchymatous cells. The bundle sheath cells have larger chloroplasts, lacking inter granal lamellae, and starch grains, while the mesophyll cells have small chloroplasts with grana. The anatomy is thus especially suited to increase carbon fixation efficiency due to the arrangement, so it is called Kranz anatomy from the German for "wreath".

Adaptive and Ecological Significance

The adaptations and ecological significance of the C3 and C4 plants include:

C3 vs C4 Pathway NEET MCQs (With Answers & Explanations)

Important topics for NEET are:

• C3 vs C4 Pathway

• Kranz Anatomy

Practice Questions for NEET

Q1. Phosphoenol pyruvate (PEP) is the primary CO2 acceptor in:

1. C3 plants

2. C4 plants

3. C2 plants

4. C3 and C4 plants

Correct answer: 2) C4 Plants

Explanation:

Phosphoenolpyruvate (PEP), a three-carbon chemical found in mesophyll cells, is the main CO2 acceptor.
Bicarbonate ions are the form in which the CO2 is received.
Bicarbonate is created when carbonic anhydrase hydrates CO2.
The PEP carboxylase or PEPcase enzyme is in charge of this fixing.
It is crucial to note that the RuBisCO enzyme is absent from mesophyll cells.
The mesophyll cells produce the C4 acid OAA.
Other 4-carbon compounds, such as aspartic acid or malic acid, are subsequently formed in the mesophyll cells and transferred to the bundle sheath cells.

Hence, the correct answer is option (2) C4 plants

Q2. Which of the following enzymes catalyses primary CO2 fixation in the C4 pathway?

1. Alsolase

2. PEP carboxylase

3. RuBP carboxylase

4. Isomerase

Correct answer: 2) PEP carboxylase

Explanation:

During the C4 pathway, CO2 combines with 3 the carbon compound phosphoenol pyruvate to form 4 the carbon compound oxaloacetic acid. This reaction is catalysed by PEP carboxylase. The formation of oxaloacetic acid occurs in the mesophyll cells and helps minimize photorespiration. Oxaloacetic acid is then converted into malate or aspartate, which is transported to bundle sheath cells for further processing. This adaptation allows C4 plants, such as maize and sugarcane, to maintain high photosynthetic efficiency in arid environments.

Hence, the correct answer is option 2) PEP carboxylase

Q3. Identify the incorrect statement in relation to C4 photosynthesis

1. Kranz anatomy is an essential feature for c4 plants

2. C4 plants have higher water use efficiency than C3 plants

3. Photorespiration can be minimized when C4 the pathway is in operation

4. Conversion of oxaloacetate to malate occurs in the bundle sheath cells

Correct answer: 4) Conversion of oxaloacetate to malate occurs in the bundle sheath cells

Explanation:

The mesophyll cells, not the bundle sheath cells, in C4 plants are where oxaloacetate is converted to malate. After that, malate is sent to the bundle sheath cells, which release CO₂ in preparation for the Calvin cycle. C4 plants have Kranz anatomy, which aids in the fixation of CO2. Compared to C3 plants, C4 plants use water more efficiently. Photorespiration is reduced via the C4 pathway.

Hence, the correct answer is option 4) Conversion of oxaloacetate to malate occurs in the bundle sheath cells.

Also Read:

• MCQs on C4 Pathway

• Difference between C3 and C4 Pathway

• Cyclic Photophosphorylation