What is Glycogenesis?

Image Credit: 
Main Image: 

Before understanding the process of Glycogenesis, it is important to know what glycogen is essentially used for. Food gets assimilated in the body as glucose and gets released as energy to perform any kind of work or effort. Glycogen can be defined as a molecule of glucose that gets stored in the vital organs of the body like liver, muscle cells, brain and kidneys. This glycogen is released from the vital organs into the body only when the glucose in the blood (coming from the carbohydrates in a diet) gets used up for all the activities. In that situation, the body is in a low-blood glucose level and needs additional energy immediately which is when glycogen gets absorbed and used up. Hence glycogen is a very important aspect of one’s effective bodily activities.




What is the definition of Glycogenesis?

Glycogenesis is an important metabolic activity in which molecules of glucose in the body is converted to glycogen in order to be stored in the liver etc. In theory, it is defined as a process in which glucose molecules are added to glycogen chains. Glycogenesis is activated when the body is in a state of rest or during high glucose level in the blood (due to high carbohydrate diet or due to diabetes) thus making insulin activate this process to reduce blood sugar level. However the synthesis of glycogen largely depends on the energy and glucose levels in the body.


What are the steps involved in Glycogenesis?

There are 2 steps in glycogenesis. Glucose is first converted into glucose-6-phosphate by the action of glucokinase. This glucose-6-phosphate is converted into glucose-1,6-bisphosphate by phosphoglucomutase and later into glucose-1-phosphate.


  1.  The first step involves synthesis of UDP-glucose from glucose-1-phosphate when catalyzed by UDP-glucose pyrophosphorylase. The water present in this reaction gives way to hydrolysis process which converts pyrophosphate to orthophosphate thus making this first step a non-reversible reaction.
  2. The UDP-glucose thus produced is catalyzed by glycogen synthase in which it gets attached to the hydroxyl group forming α-1,4-glycosidic link. This binding requires a protein like glycogenin which contains the glycogen branching enzyme.



How is glycogenesis regulated in the body?

Glycogenesis depends a lot on the blood glucose levels and glycogen levels in the liver etc. But it should be noted that glycogenesis responds to hormonal activity in the body. The various enzymes produced in the body under hormonal activity aide in regulating the glycogen levels. These are Adrenaline, Insulin and Calcium ions.

  • Adrenaline : Adrenaline levels in the body inhibit glycogen synthase and activate glycogen phosphorylase. Thus the energy demand and the rate of energy burn out are regulated thus making way for optimized glycogenesis and is also known as co-ordinate reciprocal control.
  • Insulin : Contrary to adrenaline, Insulin has an opposite effect. When insulin binds to the protein primer, the glycogen synthase converts to non-phosphorylated form. The result of this active glycogen synthase is that it decreases blood sugar level even after a carbohydrate-rich meal. This is the reason why insulin is so important in regulating blood sugar levels in our body. When insulin is not effectively produced in the body, it results in diabetes.
  • Calcium ions : Calcium ions act as secondary messengers which activate glycogen phosphorylase and inhibit glycogen synthase very much like the effects of Adrenaline. What this essentially means is that inhibition of glycogen phosphorylase is an effective method of treating type-2 diabetes. Hence high adrenaline rush or calcium levels in the body can cause high sugar levels in the body leading glycogen to get stored in excess in the liver. This is harmful after a certain limit. This also explains why diabetics are generally diagnosed with conditions of hypertension and anxiety apart from carbohydrate and sugar-rich diet.



External References
Related Videos: 
See video
Related Videos: 
See video
Related Images: