The body requires a constant supply of energy to carry out its various metabolic processes. Digested carbohydrates are converted to glucose, which are then absorbed and transported via the portal circulation to the liver where it is used to provide energy. Erythrocytes and neurones can only use glucose for fuel and therefore the maintenance of blood glucose levels is required to provide a constant energy source for these cells. However too much glucose in the blood can be very damaging, interfering with blood circulation, and causing oxidative stress.
Excess glucose above immediate requirements is converted to the insoluble form of glycogen, and stored in the liver and skeletal muscles. There is a limit to the amount of glycogen that can be stored and therefore any excess is converted into fats and stored within adipose tissue as triglycerides. When blood glucose levels drops the glycogen is broken down into glucose. Once depleted the body will draw on other forms (fats and protein) for energy.
ATP (adenosine triphosphate) is the energy currency utilised by the body. The body creates this energy supply through a number of processes, initially through the breakdown of Glucose. In the initial stage (glycolysis), it requires no oxygen for the process to take place and is therefore termed anaerobic (without oxygen). During this process the glucose is converted into Pyruvic acid and a limited amount of energy is created. When no oxygen is present the pyruvate is then broken down to form lactic acid. The lactic acid can be converted back into pyruvate. During strenuous exercise the oxygen supply is unable to keep up with demand resulting in a build up of lactic acid which limits the functioning of the muscles. This helps to prevent damage to the muscles through overwork. If sufficient oxygen is present the pyruvate will enter the mitochondria of the cell and is then converted into Acetyl CoA which then enters the Krebs cycle. During these two stages of glycolysis and the Krebs cycle the body requires; magnesium, vitamins B1,B2,B3,B5 and Lipoic acid. The final process in the production of energy involves the electron transport chain. During this process a high amount of energy in the form of ATP is created. Nutrients required during this stage are: Iron, Copper, Sulphur and Co enzyme Q10 (CoQ10). Zinc, Vitamins C and K also play a significant role.
When glucose is unavailable, the body can utilise its storage of fats to produce energy. Fats are broken down and converted into acetyl CoA and then enter the Krebs/citric cycle. Fatty acids require Carnitine to facilitate the fatty acids entering the mitochondria. Carnitine production is dependent upon Vitamins; C, B3, B6 and Iron. Muscle cells are also dependent upon Creatine for energy storage. The glycerol component of fats can also be used for energy through being converted into glucose in the liver and entering the glycolysis pathway. When glucose is unavailable, the brain is able to use Ketone bodies which are produced from the breakdown of fats. However Ketone bodies in excess are harmful to the body, and it will get rid of the excess created through the urine. Proteins in the form of amino acids are also a potential source of energy. They are used only when other energy sources are low, as in starvation. The amino acids enter the energy production system at different stages. Some amino acids can be converted to glucose and enter glycolysis. Others are converted to pyruvic acid, Acetyl CoA, or oxaloacetic acid. During the breakdown of the amino acids, ammonia is released. High concentrations of which are toxic to the body and the urea cycle processes the ammonia facilitating its excretion through urine.
Providing the necessary cofactors, Lipoic acid, Coenzyme Q10, Carnitine, Vitamins; B1, B2, B3, B5, K, magnesium, phosphorus and sulphur
The necessary transport molecules; Vitamin B2 and B3
Intermediate metabolites; citrate, succinate, malate, fumarate, oxaloacetate, Alph-ketoglutamate, isocitrate, and cis-aconitate.
- Antioxidants; glutathione, cystein, Vitamin E, Vitamin C, carotenoids, flavonoids, zinc, copper, selenium and manganese, co enzyme Q 10, lipoic acid
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