BCEM 393 Lecture Notes - Lecture 12: Glycogen Phosphorylase, Glycogenolysis, Phosphoglucomutase
14 Jun 2018
School
Department
Course
Professor
Gluconeogenesis
THE IMPORTANCE OF GLUCOSE
- It is the only fuel that the brain uses under non starvation conditions
- The whole body needs ~ 160g glucose/day, of that the brain uses 120 g
- It is the one fuel that red blood cells can use at all
- There is ~ 20g of glucose in the body —> ~ 190g available from glycogen —> enough for 1
day
HOW DO WE MAINTAIN LEVELS OF GLUCOSE IN FASTED STATES?
- Glycogenolysis
- In liver and muscle
- Process of breaking down glycogen to make glucose
- Gluconeogenesis
- In liver and kidney
- Process of generating glucose from pyruvate
TO DEAL WITH STARVATION: GLYCOGENOLYSIS
- Glycogen phosphorylase: (alpha 1->4) glycosidic linkages undergo attack by an inorganic
phosphate, removing the terminal glucose residue as alpha-D-glucose-1-phosphate
- Transferase: transfers 3 glucose residues from the branch to a nearby non reducing end as
an (alpha 1->4) linkage
- The single remaining glucose residue is released as free glucose
- At a point 4 glucose residues away from an (alpha1->6) branch point, glycogen deb ranching
enzyme is required
- Glucose residues are removed one by one from the non reducing ends by enzymes
- If there are many non reducing ends, there is a more rapid mobilization of energy
GLYCOGENOLYSIS
- Glucose 1-phosphate, the end product of the glycogen phosphorylation reaction, is converted
to glucose 6-phosphate by phosphoglucomutase
TO DEAL WITH STARVATION: GLUCONEOGENESIS
- Definition: the synthesis of glucose from non-carbohydrate precursors, including lactate,
glycerol, and amino acids
- Function: to generate glucose
IS GLUCONEOGENESIS THE REVERSE OF GLYCOLYSIS?
- Glycolysis: glucose —> pyruvate
- Gluconeogenesis: pyruvate —> glucose
- The equilibrium of glycolysis lies far on the side of pyruvate formation
- More favourable standard free energy
GLUCONEOGENESIS IS NOT THE REVERSE OF GLYCOLYSIS AT THE IRREVERSIBLE STEPS
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
It is the only fuel that the brain uses under non starvation conditions. The whole body needs ~ 160g glucose/day, of that the brain uses 120 g. It is the one fuel that red blood cells can use at all. There is ~ 20g of glucose in the body > ~ 190g available from glycogen > enough for 1 day. Process of breaking down glycogen to make glucose. Glycogen phosphorylase: (alpha 1->4) glycosidic linkages undergo attack by an inorganic phosphate, removing the terminal glucose residue as alpha-d-glucose-1-phosphate. Transferase: transfers 3 glucose residues from the branch to a nearby non reducing end as an (alpha 1->4) linkage. The single remaining glucose residue is released as free glucose. At a point 4 glucose residues away from an (alpha1->6) branch point, glycogen deb ranching enzyme is required. Glucose residues are removed one by one from the non reducing ends by enzymes.
