Carbohydrate Metabolism I Flashcards
Glucokinase vs Hexokinase
Phosphofructokinase-1 (PFK-1)-catalysis
Pyruvate Kinase Catalysis
Production of F-2,6-BP
PFK1 is inhibited by ____ and activated by ____.
PFK1 is inhibited by ATP and activated by AMP.
How the liver bypasses typical ATP-mediated glycolysis inhibition
Insulin signaling generates F-2,6-BP. F-2,6-BP activates PFK-1 desite high ATP.
This generates F-1,6-BP. F-1,6-BP activates Pyruvate Kinase despite high ATP.
However, if glucagon is also present, the glucagon receptor -> cAMP -> PKA mediated phosphorylation of pyruvate kinase will deactivate this step, preventing liver fatty acid synthesis.
Phosphofructokinse-2 (PFK-2) regulation in the liver
Glycolysis net equation
Skeletal muscle glucose
Glycolysis vs Gluconeogenesis
2,3-bisphosphoglycerate generation in erythrocytes
How does the pancreas sense glucose levels?
Increased ATP blocks the K+ channel.
fructose-2,6-bisphosphate
Allosteric regulator of PFK1 in the liver. Increases in response to insulin signaling and serves as a second messenger.
Stimulates glycolysis even in the presence of high ATP levels. This is important as it allows the liver to bypass typical PFK-1 regulation in order to generate the Acetyl-CoA it needs to make fat.
Glucose levels in the fed state are ___ and drop to ___ in the fasted state.
Glucose levels in the fed state are 8 mM and drop to 4 mM in the fasted state.
The Cori Cycle
Three fates of glucose
- Storage as glycogen
- Pentose Phosphate Pathway
- Glycolysis
Phases of glycolysis
Type ___ skeletal muscle is always glucose dependent.
Type IIb skeletal muscle is always glucose dependent.
Therefore there is a high baseline Glut4 expression which is not substantially upregulated during fasting or exercise.
The red blood cell uses glucose transporter ____.
The red blood cell uses glucose transporter Glut1.
Km ~ 1 mM
Glycolysis outline
Once fructose-6 phosphate is phosphorylated, it is committed to ____ rather than ____.
Once fructose-6 phosphate is phosphorylated, it is committed to glycolysis rather than glycogen formation or the pentose phosphate pathway
The renal medulla is _____ and thus performs glycolysis due to ____.
the renal medulla is oxygen-limited and thus performs glycolysis due to lack of adequate oxygen.
Which pathway glucose proceeds down depends on the _____ of each pathway.
Which pathway glucose proceeds down depends on the activity of the rate determining step of each pathway.
In cells that lack mitochondria, or in muscle that is exercising anaerobically, ____ must be regenerated somehow to allow glycolysis to continue.
In cells that lack mitochondria, or in muscle that is exercising anaerobically, NAD+ must be regenerated somehow to allow glycolysis to continue.
In this case, the electrons are transferred from NADH to pyruvate itself, producing lactate and regenerating NAD.
In the ____, ____, and the____, glucose is a preferred fuel and is used constantly.
s. In the brain, renal medulla, and the red blood cell, glucose is a preferred fuel and is used constantly.
All pathways of glucose metabolism require the same initial step, ___
All pathways of glucose metabolism require the same initial step, phosphorylation of glucose by glucokinase or hexokinase
Fates of pyruvate
Role of glucose in various tissues
Type ___ muscle can perform beta-oxidation of fatty acids as a fuel source.
Type I muscle can perform beta-oxidation of fatty acids as a fuel source.
Citric acid cycle from 10,000 ft
