GLUCOGÉNESIS (síntesis de glucógeno) [pasos y regulación]

Glucogenesis and Glycogen Synthesis

In this section, the video discusses glucogenesis, focusing on the synthesis of glycogen. It explains what glycogen is, its structure, where it is stored in the body, and the process of glycogenesis.

What is Glycogen?

• Glycogen is a polysaccharide composed of glucose units primarily found in the liver and muscles.

• Apart from skeletal muscle and liver, other tissues like the brain, kidneys, heart, and adipose tissue can also store glycogen.

• The liver stores approximately 90 to 100 grams of glycogen, while muscles store between 245 to 400 grams. The liver is more efficient at storing glycogen compared to muscles.

Chemical Structure of Glycogen

• Glycogen molecules have two types of glycosidic bonds: alpha 1-4 and alpha 1-6.

• Branching points in glycogen originate from alpha 1-6 glycosidic bonds.

Steps in Glycogen Elaboration

This section delves into the steps involved in glycogen synthesis within hepatic and muscular cells.

Glucose Transporters and Initial Steps

• Hepatic cells contain Glut2 transporters while muscular cells have Glut4 transporters; Glut2 transporters are insulin-independent.

• In hepatic cells, an enzyme called GlucoQ adds a phosphate group to glucose at carbon 6 to form glucose 6-phosphate using ATP.

Further Enzymatic Reactions

• Exokinase facilitates glucose 6-phosphate formation in muscle cells with magnesium as a cofactor.

Formation of UDP-Glucose

• Phosphoglucomutase converts glucose 6-phosphate to glucose 1-phosphate by transferring the phosphate group from carbon 6 to carbon 1.

Glycogen Synthesis Process

This part elucidates how UDP-glucose contributes to assembling the glycogen molecule through initiation and elongation processes.

Initiation Phase

• UDP-glucose provides a glucose unit for initiating glycogen formation catalyzed by glucogoninA.

Elongation Phase

• After initiation with a small chain of glucoses (7–12), further elongation occurs sequentially with UDP-glucose incorporation by glycogensynthase.

Regulation of Glycogenesis

The regulation of glycogenesis occurs during high-energy metabolic states when converting excess glucose into stored energy becomes favorable.

Regulatory Mechanisms

Glucose and Glycogen Functionality

This section discusses the roles of glucose and insulin in the body, highlighting how they regulate glycogen synthesis and breakdown for energy balance.

Glucose Regulation by Insulin

• When glucose levels rise, insulin levels increase to activate glycogen synthase as a protective measure against excess blood glucose.

Hormonal Regulation of Glycogen Breakdown

• Glucagon and epinephrine inhibit glycogen synthase while promoting glycogen phosphorylase activity, which degrades glycogen for energy release.

Importance of Glycogen Beyond Energy Storage

• Glycogen plays crucial roles in cellular differentiation, signaling pathways, redox regulation, and immune system function.