Carbohydrate Metabolism: Glycogen Metabolism

by Kevin Ahern, PhD

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    Any consideration of sugar metabolism must include discussion of the ways in which sugar is stored and released in the body. In animals this is glycogen and will be the subject of this talk. In the first part of the talk what I will do is go through a bit of the structural and enzymatic considerations in the breaking and making of glycogen. And in the last part of the talk, I will discuss glycogen from a regulatory point and how that regulation helps the animal to meet its needs. Now glycogen is a polymer of glucose, as I have noted in another one of the presentations. It is actually a very large polymer glucose that you can see on the screen on the right. Glycogen is stored in animals in liver and muscles. In liver it is used to provide a constant supply of glucose into the blood stream as the animal needs it. And in muscles, it’s an immediate source of glucose for the contracting actions that muscles have to take. Now glycogen is similar to amylopectin of plants and differs only in the amount of branching that the molecule has. Glycogen has branches about every 10 glucose residues. Whereas amylopectin has branches about every 50 or so. Glycogen helps to modulate blood glucose and it is; because it is that battery or that storage form of glucose, the liver can top up as necessary to release blood glucose into blood and allow that blood glucose level to stay as needed. Now glycogen in its synthesis does not start with the glucose, it actually starts with a protein called glycogenin, and to that protein is attached the first glucose molecule. And the attachment of that first glucose molecule leads to the structure that you see here. As you...

    About the Lecture

    The lecture Carbohydrate Metabolism: Glycogen Metabolism by Kevin Ahern, PhD is from the course Carbohydrate Metabolism. It contains the following chapters:

    • Glycogen Metabolism - Introduction
    • Glycogen Breakdown
    • Glycogen Synthesis
    • Regulation of Glycogen
    • Insulin Signaling & Summary

    Included Quiz Questions

    1. ...is a storage form for glucose in animals.
    2. ...is similar to cellulose in structure.
    3. ...has only alpha 1,4 bonds.
    4. ...helps plants to reduce glucose concentration.
    1. ...uses phosphate to create glucose-1-phosphate from glycogen.
    2. ...removes a phosphate from glucose when it cleaves it from glycogen.
    3. ...puts a phosphate onto ADP or GDP when building glycogen.
    4. ...gets phosphate from ATP to cleave glycogen.
    1. ...interconverts glucose-1-phosphate and glucose-6-phosphate.
    2. ...adds phosphate to cleave glucose from glycogen.
    3. ...catalyzes a non-reversible reaction.
    4. ...assists debranching enzyme to remove glucose branches during glycogen breakdown.
    1. ...transfers part of a glucose branch of glycogen and releases free glucose.
    2. ...makes 1,6 bonds.
    3. ...converts 1,6 bonds to 1,4 bonds.
    4. ...converts 1,4 bonds to 1,6 bonds.
    1. ...is an activated intermediate with a high energy bond.
    2. ...is made starting with UDP and glucose.
    3. ...is a substrate for glycogen phosphorylase.
    4. ...is a substrate for branching enzyme.
    1. Glycogen phosphorylase a is the dephosphorylated form of the enzyme.
    2. Phosphorylase kinase is activated by phosphorylation.
    3. Glycogen synthase is inactivated by Protein Kinase A.
    4. The G-protein is inactivated by conversion of GTP to GDP.
    1. ...doesn’t cut cAMP in the presence of caffeine.
    2. ...catalyzes formation of cAMP.
    3. ...inhibits the production of caffeine.
    4. ...requires ATP.
    1. It stimulates release of glucose from cells.
    2. It stimulates activity of a phosphatase.
    3. It stimulates activity of glycogen synthase.
    4. It inhibits activity of phosphorylase kinase.

    Author of lecture Carbohydrate Metabolism: Glycogen Metabolism

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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