BIOMOLECULES AND METABOLISM 3. Metabolism and Its Control Prof. K. M. Chan
Dept. of Biochemistry
Chinese University
Rm 513B, Basic Medical Sciences Building
Tel: 3163-4420;
Email: kingchan@cuhk.edu.hkBCH 1002 Biochemical Aspects of Health and Disease
Glucagon
Acts on hepatocytes.
Converts glycogen to glucose (glycogenolysis).
Form glucose from lactic acid and amino acids (gluconeogenesis).
Glucose released from liver to make blood glucose increase to normal.
Hyperglycemia inhibits release of glucagon.
Caused by deficiency of insulin secretion or actions
Type I diabetes (10%) is insulin-dependent (IDDM), starts early in life and could become very severe. Due to insufficient insulin secretion and thus injection of insulin is required to save the patients’ life.
Type II diabetes (90%) is non-insulin dependent, NIDDM, which is slow to develop with milder symptoms. Insulin is produced but the cells are not responding (insulin resistant), causing many complications including obesity.
Biochemical complications of diabetes mellitus.
Both types of diabetes fail to uptake glucose, leading to hyperglycemia. Other symptoms of diabetes include thirst and frequent urination.
In IDDM, excessive glucagon level (due to lower insulin level) also reduces the level of F-2,6-BP in the liver, and inhibits glycolysis.
Gluconeogenesis and glycogen breakdown are also induced.
NIDDM produces excessive amount of glucose in blood leading to glucosuria.
Excessive glucose is thus produced into the blood leading to hyperglycemia (> 10 mM), even with glucose excreted in urine (hence named mellitus).
Tutorial Questions:
Compare gluconeogenesis and glycogenolysis, and explain how insulin affects these processes.
Explain the consequences of using low carbohydrate and high protein diet for weigh loss plan.
What is the role of leptine on dieting?
Why untreated diabetes may die?
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