Glycogenolysis, process by which glycogen, the primary carbohydrate stored in the liver and muscle cells of animals, is broken down into glucose to provide. Ultimate Guide on – Glycogenesis and its Cycle, steps, ppt, pdf, animation, diagrams and covering Difference between Glycogenesis and Glycogenolysis . Glycogen synthesis. • Glycogenolysis. • Pentose phosphate pathway. • Metabolism of other hexoses. Carbohydrate Metabolism.
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Glycogenesis is the biosynthesis of glycogen, the major storage form of carbohydrate in animals similar to starch in plants. Glucose is the major source of energy to the cells.
Glucose and its precursors like starch are supplied through the food we eat and are not reliable and continuous sources. Therefore our body has a built in mechanism which stores the excess carbohydrates we consume, in the form of glycogen which could be broken down to glucose when needed. Glycogen comes to rescue when the blood glucose drops down, a situation which prevails between our daily meals. The major sites of storage of glycogen are liver and muscle.
Although the glycogen content of liver is greater than that of muscle, three quarter of total glycogen is stored in muscles due to their mass.
Liver glycogen is synthesized in well fed states. Muscle glycogen is synthesized when the muscle glucose get depleted in intense physical exercise. Chemical structure of glycogen. UDP glucose acts as a vehicle that carries the glucose molecule which is to be added to the budding glycogen molecule.
Synthesis of UDP glucose. Glycogen synthesis cannot start from scratch. It needs a basic molecule on which the glucose residues can be added so that the chain can get elongated. Glycogen fragments which already exist can act as this primer.
In glycogen depleted condition, a protein primer called glycogenin acts as the flooring to which the glucose molecules from UDP glucose are added like bricks.
If Glycogenesis stops with the above steps, it is expected to create a long linear molecule similar to glycogenolsis of starch in plant. But this is not the case. After around 8 residues, branching begins and the branches provide more number of activated glucose residual ends for the UDP glucose to get attached to.
This results in a highly branched easily soluble glycogen molecule. This results in more number of end points for UDPglucose to add further glucose residues to it.
Thus branching enzyme results in extensively branched large glycogen molecule.
One such genetic disease is Glycogen storage disorder type 4 called as Anderson disease caused by defective branching enzyme. So the glycogen formed is a linear insoluble structure that accumulates in the cells causing liver and muscle damage.
Glycogen synthesis is strictly monitored to regulate the blood glucose level. It is activated in well fed state and suppressed in fasting. According to basis of regulation of metabolic process, the factors regulating Glycogenesis are.
In well-fed state, when the blood glucose level is high, glucose 6 phosphate the substrate for UDP glucose is also high. This allosterically increases Glycogenesis. Also during fasting, the substrate is low and there is need for glucose which causes break down of glycogen which is opposite of Glycogenesis.
Glycogen synthase, the key enzyme of Glycogenesis exists in activate dephosphorylated and inactive phosphorylated form. Hormones gpycogenesis glucagon and epinephrine are diabetogenic i. Thus they antagonize glycogen synthesis which is an effective way of reducing glyvogenesis glucose level and storing it for further use. These hormones succeeds in their function by series of biochemical reactions which results in phosphorylation of glycogen synthase enzyme rendering it inactive.
Glycogenesis – Wikipedia
Insulin is an ant diabetic hormone. It lowers the blood glucose level by stimulating the uptake of glucose by muscle cells and Glycogenesis in liver and muscle. Rajesh MD under Diabetes Information.
Article was last reviewed on August 26th, glycogenolysus Home Diabetes Information About Us. Glycogenolysis Glycolysis Gluconeogenesis Ketogenesis. March 9, at 2: Leave a Reply Click here to cancel reply.
Glycogenolysis | biochemistry |
This health website is for informational purposes only and Is not a substitute for medical advice, diagnosis or treatment. Stimulated by increased blood glucose level as in well fed state, insulin. Stimulated by fasting, between meals physical exercise, glucagon, epinephrine. Glycogen synthase is the key enzyme which is dephosphorylated in active form.
Glycogen phosphorylase is the key enzyme which is phosphorylated in its active form. Stimulated by low glucose levels like starvation, acidosis, glucagon and glucocorticoids. There are 4 key enzymes — Pyruvate carboxylase, Phosphoenol pyruvate carboxykinase, Fructose 1, 6 bisphosphatase and Glucose 6 phosphatase.