Cellular Respiration and Photosynthesis

On a regular basis, the cells of living organisms need the energy to carry out the vital activity. The universal source of this energy is the ATP that is produced due to the process of reactions in the energetic exchange. The majority of vivid organisms mainly produce ATP with the help of cellular respiration. The paper investigates the stages of cellular respiration and photosynthesis and their interaction and interdependence together with their connection with specific organelles.

Cellular respiration is a complex process that includes the division of the organic matter. The released energy of their chemical connections is stored and used by the cell. The majority of living organisms (including all plants, most animals, fungi, etc.) use oxygen in the process of cellular respiration. This kind of organisms is called aerobic. and their type of breathing is named the aerobic respiration.

There exist different stages of cellular respiration. The preparatory stage is the split of large organic molecules into more plain compounds. This process usually occurs in the digestive system and the cytoplasm of cells without the implementation of oxygen. Under the influence of digestive enzymes, polysaccharides are transmitted to monosaccharides, fats are divided into glycerol and higher carboxylic acids, proteins turn into amino acids, and the nucleic acids turn into nucleotides. Due to these processes, it is possible to release little energy that is not stored in the form of ATP and is mostly utilized as heat. Moreover, the splitting reactions require certain amounts of energy to be carried out. The substances that are formed as a result of the preparatory stage may be used by a cell both in the plastic exchange reactions and the further division designed to produce energy.

According to Scoville, the second stage of the energy exchange is named anoxic or anaerobic. It is the enzymatic division of the organic matter that earlier had been produced in the process of the preparatory stage. The oxygen is not involved at this period of cellular respiration. Moreover, the anaerobic stage may also take place without any access to oxygen. In this situation, the primary source of energy is the cellular glucose. Thus, it is necessary to take into consideration another process of glucose division that is named glycolysis. It is a multi-stage process of oxygen-free division of glucose to pyruvic acid. This reaction is caused in by specific enzymes and takes places in the cytoplasm of cells. In the process of glycolysis, each molecule of glucose is divided into two molecules of pyruvic acid. When the energy is released, the bigger part of it is used for heating, while the remaining part is carried out for the production of two molecules of ATP.

Glycolysis causes the release of only about 5% of the energy that is contained in the chemical connections of a glucose molecule. A bigger part of the energy is contained in the product of glycolysis – the pyruvic acid. Thus, according to Scoville, in the process of aerobic respiration, the aerobic stage is the final one. The pyruvic acid that is formed with the help of glycolysis is transferred to the mitochondrial matrix, where it is completely divided, and oxidized to the final product that is C02 and H20.

The article “A Primer on Photosynthesis and the Functioning of Cells” states that photosynthesis is a complex process that involves two stages: the light one that always takes place only with the help of the light and the dark one that does not have any light requirements. All the processes occur in the chloroplast. During the light stage, chlorophylls absorb the quantum of light, that results in the formation of the molecules of ATP. Meanwhile, the water is divided into hydrogen ions and molecules of oxygen.

The chloroplasts contain the chlorophyll molecules that are able to absorb the sunlight. At the same time, the light is absorbed by the other pigments that are unable to carry out the process of photosynthesis. The process of photosynthesis takes place in the restricted number of the molecules of chlorophyll. The other chlorophyll molecules, carotenoids, and other substances create special antennae that serve for capturing the light. They are able to absorb the photons of light and transmit them to the special reaction centers.

The dark phase of photosynthesis requires carbon dioxide as the primary component. Thus, the plant should constantly absorb it from the atmosphere. For this purpose, on the surface of a leaf, there are located the structures named stomata. In the process of their opening, CO2 is transmitted into a leaf, where it is dissolved in water and creates a reaction with the light stage of photosynthesis.

In the process of the light stage, the majority of plants connect CO2 with a five-carbon organic compound that results in the formation of two molecules of the three-carbon compound.

The further synthesis takes place in chloroplasts. It is a complex process that results if the formation of the six-carbon compound that may be used for the synthesis of glucose, sucrose, or starch. These forms of the organic matter serve for the accumulation of the energy of plants. Only a small part of this organic matter may remain in the leaf and serve for its vital activity. The remaining carbohydrates are transferred throughout the plant used in the places where the energy is necessary, for example, it may be the zones of growth.

It is necessary to understand that the appearance of the photosynthesis and the accumulation of the oxygen in the atmosphere has caused the appearance of cellular respiration. In the comparison with bacteria that are able only to perform the photo reduction, algae are in a much better position as they are able to carry out the process of cellular respiration. They manage to satisfy the requirements for energy and metabolites that are necessary to carry out the process of biosynthesis with the help of photosynthesis when there is enough light; in the darkness this process if replaced by the cellular respiration. The development of this feature made such organisms is completely independent of the light and able to function when there are insufficient light resources.

It is difficult to overestimate the importance of the appearance of cellular respiration that allowed the organisms to release and to store more energy. Not a single organism that was functioning only due to the process of fermentation could show the same results shown by the organisms that utilized both photosynthesis and cellular respiration. Even after the appearance of photosynthesis only, an organism was limited by the resources provided with the help of this process. Of course, such organisms were able to create the organic matter; however, this production was sufficient only for the existence, not for the storage. Photosynthesis was unable to produce sufficient energy for fermentation, so the organism did not have additional resources for its development. Cellular respiration together with photosynthesis provided the organisms with the ability not only to produce energy but also to store it for the future growth that accelerated the evolutional process.

Cellular respiration is a complex activity directed towards the division of the organic matter into the substances that provide a certain organism with the necessary nutritive products. This process is divided into several stages: the preparatory one, the anaerobic, and the aerobic stage. At the same time, photosynthesis is divided into two stages: the light and the dark ones. Together with cellular respiration, photosynthesis is able to provide an organism with energy sufficient not only for the vital activity but also for the storage. This combination accelerated the evolutionary process.