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Latest: NEET 2024 Paper Analysis
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Photosynthesis is the process through which plants use the principal photosynthetic enzyme Rubisco to convert light, carbon dioxide and water into sugars that drive plant development.C3 photosynthesis, in which the first carbon compound created contains three carbon atoms, is used by the majority of plant species on Earth. Carbon dioxide enters a plant through its stomata (microscopic pores on plant leaves), where the enzyme Rubisco fixes carbon into sugar via the Calvin-Benson cycle, which involves a series of complications.
However, photosynthesis is slowed by two major constraints.Plants, on the other hand, have evolved a different type of photosynthesis to assist lessen these losses in hot, dry climates. Unique leaf structures permit carbon dioxide to be concentrated in ‘bundle sheath’ cells and near Rubisco during C4 photosynthesis, which produces four-carbon molecules. This arrangement successfully eliminates Rubisco’s interface with the oxygen and the necessity for photorespiration by delivering carbon dioxide directly to .Furthermore, this adaptation permits plants to retain water by allowing them to fix carbon even while their stomata are closed.
C4 plants, such as maize, sugarcane and sorghum prevent photorespiration by utilising PEP during the initial step of carbon fixation. This process occurs in the mesophyll cells.
Difference between c3 c4 and CAM Pathway
| S.NO | C3 | C4 | CAM Pathway |
| 1 | The most common kind of The Calvin cycle creates three carbon compounds during photosynthesis. | Photosynthesis yields an intermediate four-carbon molecule that is divided into three carbon compounds for the Calvin cycle. | Photosynthesis that collects sunlight during the day and fixes carbon dioxide at night. |
| 2 | This only happens in mesophyll cells. | This occurs in mesophyll and bundle sheath cells. | This occurs in mesophylls. |
| 3 | This occurs in all plants. | It occurs in around 3% of vascular plants. | Occurs in plants that are suited to arid settings, such as cactus and pineapples. |
| 4 | There are no specific features to counteract photorespiration. | Reduces photorespiration by carrying out carbon dioxide fixation and the Calvin cycle in separate cells. | Reduces photorespiration by executing carbon dioxide fixation and the Calvin cycle at different periods. |
C3, C4 and CAM Pathway of carbon fixation
Global food poverty is already a major issue, so continuing to rely on inefficient food and energy sources is a risky course to take, especially since we don’t know how plant cycles will be altered as our atmosphere becomes more carbon-rich.
The evolution of C4 and CAM is assumed to have been aided by a decrease in atmospheric CO2 and a drying of the Earth’s climate, raising the worrying potential that increased CO2 will reverse the conditions that favoured these alternatives to C3 photosynthesis.Hominids can adapt their food to climatic change, according to evidence from our predecessors.
Both Ardipithecus ramidus and Ar anamensis relied on C3 plants, but as eastern Africa’s forests gave way to savannah around four million years ago, the species that survived—Australopithecus afarensis and Kenyanthropus platyops—were mixed C3/C4 consumers. Two new species had emerged by 2.5 million years ago: Paranthropus, which moved its focus to C4/CAM food sources, and early Homo sapiens, who ate both C3 and C4 plant kinds.
In the last 35 million years, the evolutionary process that transformed C3 plants into C4 species has occurred at least 66 times. This evolutionary advance resulted in improved photosynthetic effectiveness as well as more efficient water and nitrogen usage.
Significance of C3, C4 and CAM Pathway
- In the Calvin cycle, C3 photosynthesis is the most common type of photosynthesis that creates a three-carbon molecule. It can be found in all photosynthetic plants
- Photorespiration, on the other hand, occurs at a higher rate in C3 plants. C4 photosynthesis, on the other hand, is a kind of photosynthesis seen in tropical plants. It also produces a four-carbon intermediate that breaks into a three-carbon molecule for the Calvin cycle
- Because it accomplishes carbon fixation and the Calvin cycle in distinct cells, it reduces photorespiration. CAM photosynthesis, on the other hand, is a kind of photosynthesis that occurs in semi-arid environments
- Carbon dioxide fixing takes place at night in this location. Furthermore, by executing carbon dioxide fixation and the Calvin cycle at different periods, it reduces photorespiration
Conclusion
Photosynthesis is the process through which plants use the principal photosynthetic enzyme Rubisco to convert light, carbon dioxide, and water into sugars that drive plant development. C3 photosynthesis, in which the first carbon compound created contains three carbon atoms, is used by the majority of plant species on Earth. Unique leaf structures permit carbon dioxide to concentrate in ‘bundle sheath’ cells and near Rubisco during C4 photosynthesis, which produces four-carbon molecules. In the dark process, on the other hand, these two energy-dense molecules are employed to fix carbon dioxide and produce carbohydrates. As a result, carbon dioxide fixation in C3 is the first step in the Calvin cycle. CAM photosynthesis is the third type of photosynthesis that occurs in semi-arid plants.
