Metabolism Flashcards
Reactants and products of glycolysis
1 Glucose, 2 ATP –> 4 ATP, 2 NADH, 2 Pyruvate
Define GLUT
Glucose transporters allowing facilitated diffusion into cells along gradient.
Describe hexokinase step and purpose
Uses 1 ATP to phosphorylate Glucose –> G6P
Keep glucose inside cell
Irreversible so highly regulated
Purpose of Hexokinase IV
Higher Km, expressed in pancreatic B-cells
Sensor of glucose for insulin production
What is special about G6P
It can readily go into many pathways (pentose phosphate, glycolysis, glycogenesis)
How does G6P go into F6P
Fructose Isomerase (readily reversible)
Fully describe how F-6-P gets to F-1,6-bP and the regulation involved
F6P –> F1,6bP by PFK1 (using 1 ATP to phosphorylate)
PFK1 is activated by F2,6bP, which is made from F6P by PFK2
PFK is activated by insulin, and inactivated by glucagon
How does glucagon influence production of F1,6bP
It activates FBPase2, therefore inhibiting PFK2. In turn, it decreases production of F2,6bP, therefore inactivation PFK1 and limiting F1,6bP production.
How does insulin affect F1,6bP production
Insulin activates PFK2 (inactivating FPBase2), therefore increasing F2,6bP production leading to an increase in PFK1 activity. This results in more F1,6bP production.
How many points of regulation are in the preparatory phase of glycolysis and what are they
- Hexokinase phosphorylating glucose into G-6-P
- PFK1 phosphorylating F-6-P into F-1,6-P
How is NADH –> NAD+ and why is that important for glycolysis?
NAD+ needs to be an electron acceptor for steps of the glycolysis payoff phase. To convert NADH –> NAD+, the malate/aspartate shuttle moves the electrons into the mitochondrial matrix
Under anaerobic conditions, how is NADH –> NAD+
Lactate dehydrogenase converts NADH and Pyruvate into NAD+ and lactate
Describe the Cori Cycle
Lactate development in exercising muscle is transported to the liver and made back into glucose by gluconeogenesis. This is then transported back to muscle (what happens in muscle stays in muscle).
