Metabolism III Flashcards
What is the function of hexokinase at low glucose concentrations?
Sequesters glucose in the tissues (p.99)
Where is excess glucose stored at high glucose concentrations?
In the liver (p.99)
What is the net reaction for glycolysis?
Glucose + 2Pi +2ADP + 2NAD+ –> 2 pyruvate + 2ATP + 2NADH + 2H+ + 2H2O (p.100)
Name the two reactions in glycolysis that require ATP.
1.) Glucose –> Glucose 6 phosphate (catalyzed by glucokinase/hexokinase); 2.) Fructose-6-P –> Fructose 1,6, BP (catalyzed by PFK1) (p.100)
What two substrates inhibit hexokinase and glucokinase activity respectively?
Hexokinase- Glucose-6-P; Glucokinase- Fructose-6-P (p.100)
Name the two reactions in glycolysis that produce ATP.
1,3-BPG –> 3-PG and its reverse reaction; PEP –> pyruvate (via pyruvate kinase) (p.100)
What are the regulators of Pyruvate Kinase?
(+) Fructose-1,6-BP; (-) ATP, alanine
Describe the feedback system of Fructose 2,6 bisphosphate on PFK-1.
Phosphofructokinase-2 is active in the fed state and catalyzes the reaction of fructose-6-phosphate to fructose-2,6-bisphosphate. Production of Fructose 2,6 bisphosphate catalyzes the reaction of Fructose-6-phosphate to Fructose1,6bisphosphate in glycolysis (p.100)
What reaction is catalyzed by Fructose bisphosphatase-2?
Active in the fasting state, catalyzes Fructose 2,6-bisphosphate to Fructose-6-phosphate for gluconeogenesis (p.100)
Describe the activity of FBPase-2 and PFK2 in the fasting state.
Increased glucagon –> increases cAMP –> increases protein kinase A –> increases FBPase-2 and decreases PFK2 to decrease glycolysis (p.100)
Describe the activity of FBPase-2 and PFK2 in the fed state.
Increased insulin –> decreases cAMP –> decreases protein kinase A –> decreases FBPase-2 and increases PFK2 to increase glycolysis (p.100)
What cofactors are needed for the reaction of pyruvate –> acetyl CoA?
Pyruvate + NAD+ + CoA –> AcetylCoA + CO2 + NADH (p.100)
What five cofactors are required by the three enzymes of the pyruvate dehydrogenase complex?
1.) Pyrophosphate (B1, thiamine, TTP); 2.) FAD (B2, riboflavin); 3.) NAD (B3, niacin); 4.) CoA (B5, pantothenate); 5.) Lipoic acid (p.100)
What changes occur to the pyruvate dehydrogenase complex in conditions of exercise?
Increased NAD+/NADH ratio; increased ADP, increased Ca2+ (p.100)
What complex is very similar to the pyruvate dehydrogenase complex?
The alpha-ketoglutarate dehydrogenase complex; it has similar substrates and action and the same cofactors (p.100)
What reaction does alpha-ketoglutarate dehydrogenase catalyze?
Conversion of alpha-ketoglutarate to succinyl CoA in the TCA cycle (p.100)
What is the mechanism of action of arsenic poisioning?
Inhibition of lipoic acid (p.100)
What are the principle symptoms of arsenic poisioning?
Vomiting, rice water stools, garlic breath (p.100)
What is the principle symptom of a pyruvate dehydrogenase complex deficiency?
Neurologic defects, usually starting in infancy (p.101)
Describe the pathology associated with a pyruvate dehydrogenase complex deficiency.
Backup of substrate (pyruvate and alanine) cause a lactic acidosis (p.101)
Name the two purely ketogenic amino acids.
Lysine and Leucine (p.101)
What is the genetic inheritance associated with a pyruvate dehydrogenase complex deficiency?
Most cases are due to mutations in X-linked genes for the E1-a subunit of PDC (p.101)
How do you treat a pyruvate dehydrogenase complex deficiency?
Increase intake of ketogenic nutrients (e.g. high fat content or increase lysine and leucine) (p.101)
Name the four products of pyruvate metabolism.
Alanine, Oxaloacetate, Acetyl-CoA, Lactate (p.101)
What reaction does Alanine aminotransferase catalyze?
Converts pyruvate to alanine in the cytosol for the cahill cycle where Alanine carries amino groupt to the liver from muscle (p.101)
