Cellular respiration Free Essay Example, 1250 words

A nucleoside diphosphate and a free phosphate molecule are formed from the reaction. Therefore, this reaction can proceed in either direction and can be illustrated by the following chemical equation: ADP  +  Ã¢â€žâ€"  Ã¢â€ â€Ã‚  ATP  +  H2O The process of cellular respiration allows ATP molecules to be made. Therefore, living cells can access this energy by breaking up these bonds. This same energy is made available to other cells through the transportation of ATP molecules to the cells. Sometimes it is not possible to transfer the entire ATP molecule. Therefore, the phosphate group is conveyed to another molecule, which then becomes phosphorylated, and can liberate energy by releasing the phosphate molecule. It is important to be conversant with all the steps that lead to the generation of ATP in order to comprehend the effect of rotenone on cellular respiration. The Process of Cellular Respiration The initial step in cellular respiration is glycolysis where glucose, a six-carbon molecule, is changed into two three-carbon molecules known as pyruvic acid. The initial step involves the conversion of glucose into glucose-6-phosphate, which is catalyzed by the enzyme hexokinase. Glucose-6-phosphate is then converted to fructose-6-phosphate under the influence of phosphoglucoisomerase. We will write a custom essay sample on Cellular respiration or any topic specifically for you Only $17.96 $11.86/pageorder now The resultant fructose-6-phosphate is further phosphorylated to yield fructose-1,6-bisphosphate. Subsequently, aldolase catalyzes the breakdown of fructose-1,6-bisphosphate into dihydroxyacetone phosphate and glyceraldehydes phosphate. A series of five additional reactions lead to the formation of two molecules of phosphoenol pyruvate (PEP). Pyruvate kinase then catalyzes the transfer of the phosphate groups from PEP to ADP leading to the formation of pyruvate and two molecules of ATP in addition to two water molecules and two NADH molecules. Glycolysis does not require the availability of oxygen and takes place in the cell cytoplasm. The entire glycolytic pathway consumes two molecules of ATP and generates four ATP molecules. Therefore, the net amount of energy yielded is two molecules of ATP. The chemical equation that summarizes glycolysis is as follows: Glucose + 2NAD+ + 2Pi + 2ADP → 2Pyruvate + 2NADH + 2 ATP + 2 H+ + 2 H2O Figure 1: The glycolytic pathway (Garrett and Grisham 427). Pyruvic acid from glycolysis undergoes oxidative decarboxylation to form acetyl CoA, which enters the citric acid cycle. A molecule of carbon dioxide and NADH are also formed. The enzyme pyruvate dehydrogenase complex is responsible for this reaction, which may take place in the cytosol or the mitochondria (Garret and Grisham 428).