CHAPTER 24 Glycogen Degradation. Most glycogen is found in muscle and liver cells Glycogen particles...
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Transcript of CHAPTER 24 Glycogen Degradation. Most glycogen is found in muscle and liver cells Glycogen particles...
![Page 1: CHAPTER 24 Glycogen Degradation. Most glycogen is found in muscle and liver cells Glycogen particles in a liver cell section.](https://reader036.fdocuments.us/reader036/viewer/2022081511/5697bfee1a28abf838cb9c0c/html5/thumbnails/1.jpg)
CHAPTER 24 Glycogen Degradation
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Most glycogen is found in muscle and liver cellsGlycogen particles in a liver cell section
![Page 3: CHAPTER 24 Glycogen Degradation. Most glycogen is found in muscle and liver cells Glycogen particles in a liver cell section.](https://reader036.fdocuments.us/reader036/viewer/2022081511/5697bfee1a28abf838cb9c0c/html5/thumbnails/3.jpg)
The enzyme Glycogen Phosphorylase- Catalyzes phosphorolysis – Cleavage of a bond by group
transfer to an oxygen atom of phosphate
- Glycogen phosphorylase removes glucose residues fromthe end of glycogen
- Acts only on a-14 linkages of a glycogen polymer
- The product is glucose 1-phosphate, which is convertedto glucose 6-phosphate
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Figure 24.2: The glycogen phosphorylase removes single glucose units via cleavageof a-1,4 glycosidic bonds.
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Metabolism of Glucose 1-Phosphate
Phosphoglucomutase catalyzes the conversion of glucose 1-phosphate to glucose 6-phosphate
Phosphogluco-mutase
Phosphogluco-mutase
Phosphogluco-mutase
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Hormones Regulate Glycogen Metabolism
- Insulin produced by b-cells of the pancreas in response to high blood glucose (the “fed” state)
- Insulin increases the rate of glucose transport into muscle andadipose tissue via the glucose transporter (GLUT 4)
- Glucagon is secreted by the a-cells of the pancreas in responseto low blood glucose (the fasting state)
- Glucagon stimulates glycogen degradation to restore blood glucose to steady-state levels
- Epinephrine (adrenaline) is released from the adrenal glands in response to sudden energy requirements (“fight or flight”)
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Hormones Regulate Glycogen Metabolism
- Epinephrine and glucagon stimulates the breakdown of glycogento glucose 1-phosphate
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Figure 24.11: Signal transduction pathway activates glycogen phosphorylase
Amplification viacyclic AMP