by Tarek Musslimani

Created on: March 03, 2010

Our body is in a constant need for energy in order to maintain homeostasis, or to keep a constant internal environment inside our body. This homeostasis must be done through the constant supply of energy in the form of ATP and GTP which are produced in metabolism of glucose and fatty acids. In addition there must be a constant supply of building blocks for the synthesis of proteins and DNA molecules.

These building blocks are amino acids and DNA bases. Amino acids are obtained through food rich in proteins which is degraded to amino acids in the stomach. DNA bases are synthesized in the cells or are obtained from the diet in the form of DNA molecues.

Proteins are synthesized from amino acids as was mentioned earlier. There are 20 amino acids which constitute the building blocks of all proteins. about half of them are synthesized in the liver. These amino acids that are synthesized in the liver are called non-essential amino acids because our body is capable of making them.

Other amino acids are not possible for the liver to make. These are called essential amino acids. They also participate in the synthesis of proteins in the body. These essential amino acids therefore must be obtained in the diet in the form of food rich in proteins. Otherwise there will be a metabolic disease that is manifested as the lack of certain enzymes which catalyze reactions in the cell.

Glucose is an important compound for the generation of energy. This energy that is generated in processes called glycolysis and krebs cycle and oxidative phosphorylation. Glycolysis is not an efficient reaction to generate ATP. In this reaction few ATP molecules are generated.

 In krebs cycle and oxidative phosphorylation much more ATP molecules are generated. Glycolysis is important in particular for generating energy for the brain cells. The products of glycolysis enter the krebs cycle to generate more ATP molecules. Glycolysis does not require oxygen but krebs cycle and oxidative phosphorylation require oxygen for its reaction to generate ATP.

Energy for our body can also be obtained not only from the combustion of glucose, but also from the oxidation of fatty acids. Fatty acids are obtained in the diet in the form of tri-glycerdes in which are hydrolyzed to glycerol and fatty acids. The oxidation of fatty acids which are stored in fat cells or adipocytes gives a much more energy in the form of ATP than the combustion of glucose. Thats why fats predisposes to obesity.

Glucose is the ultimate source

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