Glycogenolysis Flashcards
What is the first step in glycogenolysis
Glycogenolysis is the pathway involving the breakdown of glycogen into glucose -1-phosphate and glycogen. The glycogen chain will have a non-reducing end where C4 has an OH substituent. The enzyme glycogen phosphorylase and Pi will remove the glucose unit from the end of the chain, which results in a glucose -1- phosphate and the remainder of the glycogen chain. The non-reducing end can continue to be cleaved.
What happens in glycogenolysis when a chain is reached?
When a branch is reached, the de-branching enzyme will move the polymer of that chain down to the non-reducing end of the rest of the chain (Transferase activity) and will cleave the final glucose unit which is released as a single glucose monomer that is not phosphorylated (Hydrolyses the α1-6 linkage).
How is glucose -1- phosphate converted to glucose -6- phosphate in glycogenolysis
It is done through moving the phosphoryl group using phosphoglucomutase, which first adds a second phosphoryl group to the monomer at C6, then removes the phosphoryl group at C1, effectively moving the phosphate to make glucose -6- phosphate which is much more useful to the body. This step is freely reversible.
How is the first step in glycogenolysis regulated?
Allosterically and hormonally
How might a lack of glucose affect long-distance runners?
Long-distance runners do not allow time for glycogenolysis to happen fast enough to replace the blood glucose they’re using, which results in low blood glucose. This can result in runners becoming disoriented, unbalanced, and sometimes even collapse.
