Glucolysis Regulation (Week 5) Flashcards
In glycolysis, what are the essentially irreversible enzymes?
Hexokinase
Phosphofructokinase
Pyruvate kinase
What are the cellular advantages for phosphorylating glucose?
Maintains the concentration gradient.
The phosphate adds a charge so it cannot cross the membrane and leave the cell.
In the muscle, how is reaction one of glycolysis regulated?
The hexokinase enzyme is inhibited by glucose-6-phosphate (the substrate). So when the concentration of g-6-p get too high, glycolysis is stopped.
In the muscle, how is reaction three of glycolysis regulated?
The energy needs of the cell dictate whether glycolysis will continue at this step. If low ATP and high AMP, then glycolysis will be stimulated.
As more ATP is released, more AMP is also reduced.
Adenylate kinase inter converts ADP, ATP AND AMP, to maintain an equilibrium. When the cell is low on ATP, 2 ADP’s are used to create an ATP.
In the muscle, how is reaction ten of glycolysis regulated?
When there is low energy (high AMP) pyruvate kinase is activated.
Fructose-1,6-biphosphate activated pyruvate kinase
Acetyl-CoA inhibits pyruvate kinase
In the liver, how is reaction one of glycolysis regulated?
Hexokinase IV (glucosekinase) is found only in the liver and has a much higher Km of around 10mM. So, when glucose levels are high, these properties enable the liver to produce G-6-P for the conversion to G-1-P for glycogen production, and pyruvate for fat production.
How does insulin help respond to changes in glucose levels.
The secretion of insulin causes the body’s cells to take up glucose from the blood and store it as glycogen, and stops the use of fat as an energy source.
How does glucokinase work as a glucose sensor and drug target for diabetes?
In islet beta cells, glucokinase senses glucose levels, leading to an insulin response.
How can diabetes be genetic?
People with a low GK activity (which can be genetic) have an impaired insulin response.
In the liver, how is reaction three of glycolysis regulated?
Citrate acts as an inhibitor and reports on the status of the citric acid cycle.
Fructose 2,6 bisphosphate acts as an activator and helps the liver respond to glucose levels.
In the liver, how is reaction ten of glycolysis regulated?
Liver pyruvate kinase is turned off when glucagon is secreted, as glucagon shows low blood sugar levels, so we don’t want to use that glucose.
