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C4 Pathway

C3 Pathway

Difference Between C3 and C4 Pathway

The plants exhibiting the C4 pathway are called C4 plants and comprise 3% of flowering plants, which include maize, sorghum, sugarcane, and some other dicot plants. This pathway is also known as Hatch and Slack cycle because four carbon molecules (oxaloacetate) form as the first product of carbon fixation in plants. The C4 carbon fixation is evolved in such a way that it adapts to high light intensities, high temperatures, and dryness.

Photorespiration is not energy demanding, but leads to a net loss of CO2. Plants have developed different ways to cope with this problem of photorespiration. C4 photosynthesis is one of the successful ways evolved by plants to reduce photorespiration. C4 plants use PEP carboxylase to capture CO2 in the mesophyll cells. Instead of using CO2 in mesophyll cells, PEP carboxylase utilizes bicarbonate.

In Mesophyll Cell

  • The CO2 entering the mesophyll cells from the atmosphere will be converted to bicarbonate by hydrating CO2 using carbonic anhydrase. This bicarbonate will bind with Phosphoenol Pyruvate (PEP) in presence of PEP carboxylase to form oxaloacetate.
  • Oxaloacetate is the first stable compound having four carbons, so the pathway is C4 pathway. Then OAA is reduced to malate or aspartate which are four carbon compounds.

In Bundle Sheath Cell

  • The malate/aspartate enters bundle sheath cells and releases CO2 inside bundle sheath through decarboxylation.
  • The released CO2 is immediately fixed by RuBisCO which will be followed by a normal Calvin cycle.
  • The remaining 3 carbon compounds Pyruvate formed after decarboxylation of malate will return to the mesophyll cell for next C4 cycle using energy in the form of ATP.
  • Photorespiration is a major problem for plants in hot climates as it consumes O2 and releases CO2. During hot conditions, the plants close the stomata to conserve water but this leads to a drop in the CO2 concentration within the leaf, favoring photorespiration.

C3 and C4 Pathways

C3 and C4 are photosynthetic pathways present in terrestrial plants. C3 plants use the C3 pathway or Calvin cycle, and C4 plants use the C4 pathway, or Hatch-Slack pathway, for the dark reaction of photosynthesis. Photosynthesis is the process in which different bacteria like cyanobacteria and eukaryotes like green plants, and algae can convert solar energy to chemical energy. In this process, solar energy is absorbed and used to synthesize carbohydrates from carbon dioxide and water.

Table of Content

  • What are C3 and C4 Pathways?
  • C3 Pathway
  • C4 Pathway
  • Difference Between C3 and C4 Pathway
  • FAQs on C3 And C4 Pathways

Similar Reads

What are C3 and C4 Pathways?

C3 and C4 are photosynthetic processes found in terrestrial plants. The alternative pathway to the Calvin cycle is C4, and C3 is also referred to as the Calvin cycle. As the initial byproduct of carbon dioxide fixation, most plants generate 3-phosphoglyceric acid (PGA), a 3-carbon acid. This kind of process is referred to as the Calvin cycle or C3 pathway. A C4 plant begins the Calvin-Benson cycle of photosynthesis by fixing CO2 into a molecule with four carbon atoms. The Hatch-Slack route is another name for the C4 pathway....

C3 Pathway

C3 carbon fixation is one of the three metabolic pathways involved in carbon fixation in photosynthesis; the others are C4 and CAM. The plants that contain C3 photosynthesis are called C3 plants, and they include 95% of all plants on earth. Plants that exhibit this process depend on those areas where sunlight intensity is moderate, temperature is moderate, and CO2 is around 200 ppm or higher....

C4 Pathway

The plants exhibiting the C4 pathway are called C4 plants and comprise 3% of flowering plants, which include maize, sorghum, sugarcane, and some other dicot plants. This pathway is also known as Hatch and Slack cycle because four carbon molecules (oxaloacetate) form as the first product of carbon fixation in plants. The C4 carbon fixation is evolved in such a way that it adapts to high light intensities, high temperatures, and dryness....

Difference Between C3 and C4 Pathway

The differences between C3 and C4 Pathways are stated below:...

Conclusion – C3 and C4 Pathways

Most of the plants show the C3 mechanism for carbon fixation during photosynthesis. However, one of the important enzymes involved in carbon fixation RuBisCO has both carboxylase and oxygenase activity. And during certain conditions, instead of acting as carboxylase, RuBisCO acts as oxygenase leading to photorespirations that will result in loss of huge energy. To avoid additional loss of energy through photorespiration, plants have evolved a C4 mechanism which will avoid the losses during photosynthesis. Although C3 plants are more common in nature than C4 plants, C4 plants are found to have more photosynthetic activity due to more efficient use of CO2 and light. Understanding the mechanisms of C3 and C4 mechanisms will help in the increase in productivity of plants....

FAQs on C3 And C4 Pathways

1. Difference Between C3 and C4 Pathway?...

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C3 Pathway

Difference Between C3 and C4 Pathway