Cellular respiration is a term used to describe a set of metabolic reactions that transform the cells’ biochemical energy into adenosine triphosphate (ATP). However, these reactions are catabolic since they break down large molecules of nutrients into small particles characterized by strong molecular bonds. Cellular respiration is one particular mechanism through which cells produce chemical energy important for cellular activities. Based on this assertion, cellular respiration is considered an exothermic redox reaction since it initiates the release of heat. In animal and plant cells, nutrients are normally stored in the form of fatty acids, sugar and amino acids. In this particular case, oxygen is used as the oxidizing agent capable of converting this chemical energy into ATP.
Mitochondria are organelles in the eukaryotic cells where cellular respiration metabolic reactions take place. They are the main elements responsible for the production of ATP. Mitochondria is an organelle characterized by two membranes constituted by proteins and phospholipids. In its structure, the outer membrane is thin and permeable for the free movement of ions and energy molecules. The outer membrane is primarily made up of porins responsible for the movement of particles ( Hill, 2014). Mitochondria also consist of the inner membrane which is made up of numerous folds called cristae. These numerous folds create a large surface area for the effectiveness of metabolic reactions. Also, the mitochondria consist of the matrix which is a fluid harboring DNA and ribosomes. Granules are also part of the mitochondria matrix responsible for controlling ion concentration.
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In the mitochondria, there exists a series of chemical reactions known as metabolic pathways. In this reactions, the product of one enzyme is used as a substrate in the next cycle of reaction. It is also important to note that the location of pathway execution determines its relevance in the cell. In cellular respiration, glycolysis, electronic transport, and citric acid cycle are three major pathways. Essentially, the first step of glycolysis occurs in the cytoplasm of the cell where pyruvate molecules and ATP are produced through the fermentation process. However, the other subsequent stages of glycolysis occur in the mitochondria matrix. The inputs of a glycolysis pathway include; ATP, NAD+, glucose and four molecules of ADP+P (Hill, 2014). Two molecules of pyruvate, NADH, water, and ATPs are the main outputs of the glycolysis pathway. After the glycolysis phase, the preparatory pathway is initiated through the input of two pyruvate molecules, CoA and NAD+ (Hill, 2014). This process results in the production of molecules of carbon dioxide, NADH ions, and CoA.
The Krebs cycle which is another main pathway of cellular respiration occurs in the matrix of the mitochondria. It is also known as the citric acid cycle. It is responsible for the production of NADH, ATP, FADH and carbon dioxide as the main outputs ( Hill, 2014). However, it is worth to note that the Krebs cycle is normally initiated by the input of FAD, ADP+P, oxaloacetate, CoA and NAD molecules (Hill, 2014). Lastly, the electronic transport pathway occurs in the cristae of the mitochondria. ETC and the process of chemiosmosis are achieved by having a series of electron carriers which require oxygen as the last acceptor for effective pumping of hydrogen ions from a high concentration gradient. The electronic transport pathway receives molecules of NADH and FADH2 which are the main products of the Krebs cycle. With these products, the electronic transport chain outputs 34 ATP, FAD and NAD molecules through its action in the cristae (Hill, 2014).
Cellular respiration is an important aspect for living organism since it provides them with energy to accomplish body functions. It also helps to cushion single-celled organism from depletion of resources since fermentation alone provides them with enough energy. For instance, anaerobic respiration is very instrumental in cases where intense muscle activity is required (Hill, 2014). Therefore, for athletes, the effectiveness of cellular respiration is very important since there is a need to limit oxygen utilization. Cellular respiration also provides a mechanism through which poisonous products such as carbon dioxide are exiled from the body. Even though cellular respiration is slow, it provides a means through which large unstable glucose molecules are broken down into small energy molecules that can easily be transported.
Reference
Hill, G. E. (2014). Cellular respiration: the nexus of stress, condition, and ornamentation. Integrative and comparative biology , 54 (4), 645-657 .
