Carbon Fixation

A carbon fixation pathway found in low-latitude plants, such as grasses, that have adapted to withstand high temperatures and light intensity. The four-carbon chemical oxalo-acetate (OAA) is the first product formed when CO2 carboxylates an acceptor molecule called phosphoenolpyruvate (PEP). After that, the compounds are employed to store energy and provide structure for other biomolecules. Carbon is typically fixed by photosynthesis, however in the absence of sunshine, certain species employ a process called chemosynthesis. This process is vital for plants in our plants for their survival, as without all these processes it would be a disaster for them.

An Explanation About Carbon Fixation-

Now we will read more about carbon fixation, its types, the total amount of fixation in the atmosphere and lastly, we will read about total carbon fixation in the biosphere.

Carbon fixation-

Carbon fixation is the way to incorporate carbon dioxide into organic molecules (most often carbohydrates) in order to prevent it from escaping into the environment as a free gas. Energy is produced as a consequence. Carbon fixation, often known as CO2 assimilation, is the process through which photosynthetic organisms (such as plants) transform inorganic carbon into organic molecules (carbohydrates). 

CO2 fixation, for example, is a kind of carbon fixation in which carbon dioxide from the atmosphere is converted into carbohydrates. It is, in fact, the first critical step of the Calvin Cycle. Carbon fixation is critical in the photosynthesis process. Without the Calvin cycle, photosynthesis would be impossible, and plants would be unable to manufacture their own food.

Its types-

There are 3 types of carbon fixations- C3, C4 and CAM

C3 –

The Calvin cycle’s initial phase is the C3 carbon fixation pathway. It starts with the enzyme rubisco catalyses the carboxylation of Ribulose-1,5-bisphosphate by CO2, resulting in the highly unstable 6-carbon intermediate 3-keto-2-carboxyarabinitol 1,5-bisphosphate, which splits instantly into two molecules of the more stable 3-phosphoglycerate, a three-carbon organic compound.

C4 –

The enzyme PEP carboxylase adds CO2 to phosphoenolpyruvate, resulting in a four-carbon compound that is subsequently delivered to bundle sheath cells, where the CO2 is freed for use in the Calvin cycle.

Rather than direct carbon fixation as in the Calvin cycle, the C4 pathway involves mechanisms that convert pyruvate to phosphoenolpyruvate (PEP), which subsequently interacts with CO2 to form a four-carbon molecule (hence the name C4). As a consequence, photorespiration is avoided, and inefficient CO2 loss associated with the C3 carbon fixation pathway is reduced.

Plants that go through the C4 pathway first are more adapted to drought, high temperatures, and low nitrogen or CO2 concentrations than those that go through the C3 pathway first.

CAM-

A plant that adapts to dry circumstances by using the Crassulacean acid metabolism (CAM). When CO2 enters the stomata at night, it is transformed into organic acids, which then release CO2 for the Calvin Cycle during the day when the stomata are closed.

Xerophytic characteristics such as thick, decreased leaves with a low surface-area-to-volume ratio, thick cuticle, and stomata buried into pits are common in CAM plants.

Cam plants have a complex carbon fixation system in which the stomata open at night to let CO2 enter and be fixed as a four-carbon acid (i.e. malate).

The CO2 is then released throughout the day for utilisation in the Calvin cycle. The rubisco receives a high concentration of CO2, while the stomata remain closed during the warmest and driest portion of the day to avoid excessive water loss. As a result, CAM plants are well-suited to dry environments.

Orchids, cactus, jade plants, and other CAM plants are examples.

The total amount of fixation in the atmosphere-

Any natural or artificial activity that causes free nitrogen (N2), a relatively innocuous gas abundant in the atmosphere, to mix chemically with other elements to generate more reactive nitrogen compounds such as ammonia, nitrates, or nitrites, also total amount of nitrogen fixation in the atmosphere is 12.5%.

Nitrogen does not react with other elements under normal circumstances. Nitrogenous molecules, on the other hand, may be found in all fertile soils, all living organisms, many foodstuffs, coal and naturally occurring substances like sodium nitrate (saltpetre) and ammonia. Every live cell’s nucleus contains nitrogen which is one of the basic components of DNA.

Total carbon fixation in the biosphere-

First, let’s learn the meaning of biosphere-

The biosphere is a small layer of the Earth’s surface that supports life, spanning from a few kilometres into the sky to deep-sea vents. The biosphere is a worldwide ecosystem made up of living creatures (biota) and the non-living (abiotic) components that provide them with energy and nutrition.

Coming on to the total amount of carbon fixation in the biosphere is 4×1013 kgs.

Conclusion-

In this we learned about carbon fixation, its kinds, the overall quantity of fixation in the atmosphere, and finally, total carbon fixation in the biosphere. The carbon cycle is necessary for life on Earth to exist. Nature strives to maintain carbon balance, which means that the quantity of carbon naturally released from reservoirs equals the amount naturally absorbed by reservoirs. The world can stay friendly to life if this carbon balance is maintained. The existence of life on Earth as we know it would be jeopardised if the carbon cycle were to be disturbed, plants would struggle and maybe die if carbon dioxide was not there, posing a challenge for all organisms on the earth that rely on oxygen to survive.