The metabolic rate essay .docx

Regulates breathing which kick starts the aerobic

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regulates breathing which kick starts the aerobic respiration pathway, where through the process of oxidative decarboxylation, the enzyme pyruvate dehydrogenase converts pyruvate into acetyl CoA. The carboxyl group in the pyruvate in replaced with an acetyl group and thus carbon dioxide is released as a product. As the runner approaches the forty-five-minute mark, the glycogen stores are considerably depleted, at which stage the body results to using other forms of energy storage, such as fatty acid molecules. Almost 60% of the energy supply is dependent of fatty acids at this point with the carbohydrate dependence decreasing to approximately 40%. Fatty acids are a more energy rich source, with the oxidation of fatty acids such as palmitic acid producing up to 106 ATP molecules per unit, contrary to the oxidation of glucose which yields approximately 32 ATP per glucose unit. To obtain the Fatty Acid molecules for β-oxidation, triacylglycerol molecules are mobilised from the adipose tissue stores, location of fatty acid reserves. With the use of the protein Serum Albumin, the fatty acid chains are hydrolysed from the glycerol backbone and transported to target cells via the bloodstream. To aid transport across the membrane, the carnitine shuttle is utilised after which a CoA molecule is substituted onto the structure. This fatty-acyl-CoA undergoes β-oxidation to produce Acetyl-CoA. Fatty Acid oxidation can be divided into four steps, the first referring to the fatty-acyl-CoA molecule undergoing dehydrogenation, which produces the double bond within the molecule and in the process loading the electron carrier FAD to FADH2, playing an important role in the electron transport chain later on. A hydroxyl group is formed by breaking the aforementioned double bond, after which the hydroxyl group is oxidised to a carbonyl bond. During this process, the Nicotineamide-Adenine-Dinucleotide (NAD+) was reduced to NADH. The final part of this process was the production of HSCoA via thiolysis, resulting in the splitting of acetyl CoA molecule to be used in the Citric Acid Cycle.
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The acetyl CoA produced from the two sources, fatty acids and carbohydrates, enters the citric acid cycle, where it undergoes condensation along with oxaloacetate into citrate by being catalysed by citrate synthase. This reaction is highly exergonic as a result of the high energy thioester bond despite the generally low concentration of oxaloacetate. Citrate is
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