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Carbohydrate Metabolism.

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Introduction

Carbohydrate Metabolism Blood glucose level is maintained at approximately 90mg glucose per 10cm blood. Low levels of glucose would be damaging because some tissues cannot, such as the brain store glucose. Low blood sugar level is called hypoglycaemia and causes hunger, sweating, irritability and double vision. High blood sugar level is called hyperglycemia and causes breakdown of muscle tissue, loss of weight and tiredness. A rise in blood sugar level is detected by the � cells in the pancreas, which in response produce more insulin. Sugar enters the liver from the gut by the hepatic portal vein. This is the only blood vessel in the body having extremely variable sugar content. All hexose sugars are converted to glucose by the liver and stored as insoluble polysaccharide glycogen. Converting Glucose to glycogen is called Glconegenesis and is stimulated by the presence of insulin. Insulin is a small protein composed of 51 amino acids. ...read more.

Middle

A decrease in the level of gluconeogenesis, the production of glucose. During times of low blood sugar level such as after exercise, glycogen is broken down to glucose to prevent the blood glucose level falling below 60mg per 100cm3 blood. This process is called gluconeogenesis and involves the activation of phosphorylase enzymes by the hormone glucagon. Glucagon is made in the pancreas and is released when blood sugar level falls. It is a protein composed of 299 amino acids and is released along with several other hormones in response to a fall in blood glucose level below normal. Receptor sites in the liver cell membrane bind to glucagon, which activates adeny cycles to form cyclic AMP. The action of cyclic AMP activates phosphorylase enzymes, which stimulate the break down of glycogen to glucose. Glucagon has no effect on muscle glycogen. Regulation of glucagon secretion is by alpha cells in the pancreas responding to falling glucose levels. ...read more.

Conclusion

Glconegenesis occurs when the demand for glucose has exhausted the glycogen store in the liver. Glucose can be synthesised from non-carbohydrate sources. Low blood sugar levels stimulate the sympathetic nervous system to release adrenaline which helps satisfy immediate demand. Low blood sugar levels also cause the release of CRF from the hypothalamus, which then causes the release of adrenocorticotrophic hormone ACTH from the anterior pituitary. This causes the release of more glucocrtiocoid hormones- cortical know as hydrocortisone. These stimulate the release of amino acids, glycerol and fatty aids, present in the tissues into the blood and increase the rate of synthesis of the enzymes in the liver, which convert amino acids and glycerol into glucose. Carbohydrates in the body, which cannot be used or stored as glycogen, are converted into fats and stored. IT has been estimated that the Liver carriers out several hundred separate functions involving thousands of different chemicals. Carbohydrate metabolism is just one Liver function, which ensures the cells of the body are supplied with constant glucose to meet their demands. ...read more.

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