Glycogen Phosphorylase quiz #1 Flashcards
Glycogen Phosphorylase quiz #1
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What reaction does glycogen phosphorylase catalyze, and why is this reaction important for cells?
Glycogen phosphorylase catalyzes the breakdown of glycogen into glucose 1-phosphate, which is important because the released glucose can be used in cellular respiration to generate ATP, providing energy for the cell. What are the two main isozymes of glycogen phosphorylase, and how do they differ in their regulation?
The two main isozymes are liver glycogen phosphorylase and muscle glycogen phosphorylase. They are catalytically similar but differ in allosteric regulation: the liver isozyme is usually active, while the muscle isozyme is usually inactive and only becomes active during muscle contraction. How are the phosphorylase a and phosphorylase b forms of glycogen phosphorylase interconverted, and what is the significance of this conversion?
Phosphorylase a and phosphorylase b are interconverted through covalent regulation by phosphorylation and dephosphorylation of specific serine residues. Phosphorylase a (phosphorylated) is more active, while phosphorylase b (unphosphorylated) is less active. In which form and state does liver glycogen phosphorylase predominantly exist under normal conditions, and what does this imply about its activity?
Liver glycogen phosphorylase predominantly exists in the phosphorylase a form and the R (relaxed) state under normal conditions, meaning it is usually active and ready to catalyze glycogen breakdown. Why is muscle glycogen phosphorylase typically inactive, and under what condition does it become active?
Muscle glycogen phosphorylase is typically inactive (in the phosphorylase b, T state) and becomes active during muscle contraction, when it is allosterically and covalently regulated to provide glucose for ATP production. What reaction does glycogen phosphorylase catalyze, and why is this reaction important for cells?
Glycogen phosphorylase catalyzes the breakdown of glycogen into glucose 1-phosphate. This reaction is important because the released glucose can be used in cellular respiration to generate ATP, providing energy for the cell. What are the two main isozymes of glycogen phosphorylase, and how do they differ in their regulation?
The two main isozymes are liver glycogen phosphorylase and muscle glycogen phosphorylase. They are catalytically similar but differ in allosteric regulation: the liver isozyme is usually active, while the muscle isozyme is usually inactive and only becomes active during muscle contraction. How are the phosphorylase a and phosphorylase b forms of glycogen phosphorylase interconverted, and what is the significance of this conversion?
Phosphorylase a and phosphorylase b are interconverted through covalent regulation by phosphorylation and dephosphorylation of specific serine residues. Phosphorylase a (phosphorylated) is more active, while phosphorylase b (unphosphorylated) is less active. In which form and state does liver glycogen phosphorylase predominantly exist under normal conditions, and what does this imply about its activity?
Liver glycogen phosphorylase predominantly exists in the phosphorylase a form and the R (relaxed) state under normal conditions. This means it is usually active and ready to catalyze glycogen breakdown. Why is muscle glycogen phosphorylase typically inactive, and under what condition does it become active?
Muscle glycogen phosphorylase is typically inactive (in the phosphorylase b, T state) and becomes active during muscle contraction. It is activated by allosteric and covalent regulation to provide glucose for ATP production.
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