The Many Processes Involved In Cellular Metabolism

Cellular metabolism encompasses the many processes that work together to keep the cells in dynamic equilibrium. Cellular metabolism is responsible for providing energy to the cell and is an essential element of life. There are several complex, involved processes involved in cellular metabolism including glycolysis, Krebs’s cycle, and electron transport. Metabolism itself can be broken down into two different categories: catabolic and anabolic. Catabolic metabolism involves the breakdown of large molecules such as polysaccharides, lipids, nucleic acids, and proteins into the smaller molecules of monosaccharides, fatty acids, nucleotides, and amino acids in order to obtain energy. On the other hand, anabolic reactions are when simple substances come together in order to produce complex molecules. Cellular respiration is an example of a catabolic reaction while protein synthesis is an example of an anabolic reaction. As mentioned, cellular respiration is a type of catabolic reaction in which cells produce ATP and remove waste products. Cellular respiration contains multiple steps including glycolysis, pyruvate oxidation, the Kreb’s Cycle, and the electron transport chain. Each of these complex steps are performed in order to produce
energy for the cell in the form of ATP and to help cells carry on their normal functions. The first step of cellular respiration is glycolysis. Glycolysis is a 10 step anaerobic process that produces two net ATP and takes place in the cytosol of the cell. The molecules that enter glycolysis are 2 glucose molecules, 2 NAD+, and 1 ADP+P. Glycolysis first goes through sugar activation in which glucose is converted to fructose-6-phosphate and then phosphorylated. The result of the sugar activation step is fructose-1 and 6-diphosphate, this step uses two ATP molecules. Next comes sugar cleavage phase where the fructose-1 and 6-diphosphate from the sugar activation are split into two 3-Carbon fragments. Finally comes oxidation and ATP formation. The 3-Carbon fragments are oxidized and are picked up by NAD+, then inorganic phosphate attached to the oxidized fragments and are later cleaved off. This process results in two net ATP (four total are produced, but two are used in the sugar activation phase), two pyruvate, and two NADH+H. The two pyruvate molecules produced in glycolysis lead to the step of pyruvate oxidation which takes place in the mitochondrial matrix of the cell.
The 2 pyruvate molecules from glycolysis enter as well as 2 NAD+ and 2 NADH+H+, 2 CO2, 2 Acetyle CoA are produced. In the Kreb’s cycle, which occurs in the matrix, the Acetyle CoA from pyruvate oxidation bring in 2-Carbon acetic acid is combine with 4-Carbon acetic acid to produce 6-Carbon citric acid which is the first substrate of the Kreb’s cycle. This acetic acid gets broken apart and oxidized throughout the cycle and generates NADH + H+ and FADH2. Due to the decarboxylation and oxidation processes 6CO2, three NADH + H+, and one FADH2 molecules are produced throughout the Kreb’s
cycle. The electron transport chain is the final catabolic step of cellular respiration and the most bountiful in terms of ATP production with a total of 34 ATP molecules being produced at the end of the process. This process takes place on a series of enzymes on the inner mitochondrial membrane of a cell. In the electron transport chain electrons are released from NADH and FADH2 which are passed along through enzymes and give up energy along the way. The energy these electrons produce fuels the process of chemiosmosis where H+ ions are from the inner mitochondrial membrane through active transport. In the electron transport chain, hydrogens are combined with molecular oxygen. The energy released during this reaction attaches an inorganic phosphate group to ADP producing ATP. Cellular metabolism encompasses three main steps consisting of glycolysis, the Kreb’s cycle, and the electron transport chain. In total the process yields 38 ATP molecules that the cell uses to perform its normal functions and keep the body up and running. To summarize the process of cellular metabolism, “it is the enzymatic breakdown of glucose (C6H12O6) in the presence of oxygen (O2) to produce cellular energy (ATP): C8H12O6 + 6CO2 + 6H2O + 38 ATP”