SM6 Flashcards
(14 cards)
When is glucose committed to glycolysis?
It is phosphorylated by hexokinases. This modified glucose is a branch point in glucose metabolism.
What is the key regulatory step of glycolysis?
When fructose 6-P is phosphorylated by PFK-1 to fructose 1,6 bisphosphate. This is thermodynamically and kinetically irreversible
How do we regenerate NAD during anaerobic glycolysis?
NADH is reoxidized in the cytosol by lactate dehydrogenase by the reduction of pyruvate to lactate. This is important for RBC (which don’t have mitochondria)
What is the key regulatory enzyme in glycolysis?
PFK-1. It is allosterically activated by AMP and fructose 2,6-bisphosphate (which you have when well-fed). Allosterically inhibited by ATP and citrate (which is kept high in mitochondria, so when have a lot d/t beta oxidation of FA we try to decrease glycolysis).
when is pyruvate kinase regulated?
Only in liver. The L isozyme regulated by allosteric effectors (fructose 1,6-bisphosphate and ATP) and by a cAMP-dependent protein kinase. This is a feed-forward mechanism that speeds the glycolysis pathway along.
why is it dangerous to have buildup of fructose 1-P in inherited fructose intolerance?
We utilize ATP to synthesize this compound from fructose therefore we can deplete ATP.
What is the difference between non-classical glactoosemia and classical galactosemia?
Non-classical is a problem with GALK (which catalyzes the reaction phosphorylating galactose). Classical is a problem with GALT which catalyzes the reaction converting galactose 1-P to glucose 1-P using activated UDP-Glucose
In the polyol pathway what is glucose and galactose converted to by aldose reductase?
Sorbitol; Galactitol
What does HbA1C check?
Made by glycation of hemoglobin beta chain. it measures how well glucose levels are being controlled.
What is the process of non-enzymatic reducing sugars to proteins?
Glycation to produce AGEs
Why is the pentose phosphate important?
From glucose-6-P it produces reduced NADP for other reactions and also ribose-5-phosphate for nucleotide synthesis by bypassing the first stage of glycolysis. Occurs in cytoplasm under well-fed conditions. For every mole of G6P we get two moles of NADPH
What precursors are used in gluconeogenesis?
Amino acids from proteins (mainly alanine), lactate from red blood cells and muscle and glycerol released from triacylglycerols.
The last step of glycolysis converts PEP to Pyruvate using pyruvate kinase. This is a reversible reaction that must be inhibited during gluconeogensis so that what other pathway can occur?
So the pyruvate can be acted on by pyruvate carboxylase (which uses biotin as a cofactor to carry CO2 and acetyl CoA as an allosteric activator) and converted to OAA which can either be transaminate to aspartate and transported out of the mitochondria or it can be reduced to malate and transported out where it will be converted back into OAA and converted to CO2 by PEP carboxykinase
Glycogen is degraded to and synthesized from glucose.
F. It is Glucose-1-P
