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HF B4 Gluconeogenesis and Gycogen Breakdown

Terms in this set (55)

Why must blood glucose be maintained between meals?
1. must bring blood glucose up to the normal range
2. dietary carbs maintain our blood glucose for only a few hours
How is blood glucose supplied during the fasting state (2)?
breakdown of glycogen
gluconeogenesis
What are 3 main processes that take place during the fasting state?
breakdown of glycogen
process of gluconeogenesis
use of TAG based fuels (where possible) so that blood glucose is spared for use by the brain and RBCs.
Where in the body can glycogen degradation take place?
liver and skeletal muscle
What 2 enzymes are needed for glycogen degradation?
glycogen dephosphorylase
debranching enzyme
glycogen dephosphorylase
cleaves alpha-1,4 linear linkages by phosphorlysis, releasing glucose units from non-reducing ends one at a time to produce G-1-P
What is the produce of glycogen dephosphorylase?
many individual units of G-1-P
debranching enzyme
restructures branch and, by hydrolysis, breaks the remaining alpha-1,6 linkage to remove free glucose
Which enzyme involved in glycogen degradation can break the alpha-1,6 linkage?
debranching enzyme
What are the overall products of glycogen degradation?
92% glucose-1-P
8% free glucose
What enzyme converts the glucose-1-P to glucose-6-P after glycogen degradation? Why does this happen?
phosphoglucomutase
so that the glucose molecule can be used for glycolysis
Overall process of glycogen degradation
1. glycogen dephosphorylase breaks the alpha-1,4 linkages, breaking into individual G-1-P molecules at non-reducing ends
2. Debranching enzyme breaks off all but the first monomer of a branch and translocates it to the linear structure, then breaks the final alpha-1,6 linkage to form free glucose
3. phosphoglucomutase converts all G-1-P molecules to G-6-P molecules so that they can be used for glycolysis
4a. In the liver, glucose-6-P is hydrolyzed to free glucose by glucose-6-phosphotase so that free glucose can be releasd into the blood.
4b. the muscle uses G6P from glycogen for its own energy needs
When does the glycogen breakdown process start to differ between the muscle and the liver
after formation of G-6-P by phosphoglucomutase
Why does the liver release free glucose after glycogen breakdown, but the muscle does not?
the liver contains glucose-6-phosphatase, which is not present in muscle, which can convert the glucose-6-P to free glucose. They muscle just uses glucose-6-P for its own energy needs.
gluconeogenesis
de novo synthesis of glucose
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