SCT II - Carbohydrate Metabolism I Flashcards
What are the 3 methods of NADH production in the cytosol?
Enzymatic reactions:
- Glyceraldehyde-3-Phosphate Dehydrogenase (GAPDH)
- Alcohol dehydrogenase
- UDP-glucose dehydrogenase
What are the 3 types of shuttles?
- Glycerol phosphate shuttle
- Malate-aspartate shuttle
- Lactate shuttle
What is the pathway of the glycerol phosphate shuttle?
Reduction of DHAP (Cytosol)
NADH → NAD+ = DHAP → Glycerol-3-Phopshate
Oxidation of Glycerol-3-Phosphate (IMM)
FAD → FADH2 = Glycerol-3-Phopshate → DHAP (Via IMM transporter)
What is the pathway of the Malate-aspartate shuttle?
Reduction of OAA (Cytosol)
NADH → NAD+ = OAA → Malate
Oxidation of Malate (Matrix)
NAD+ → NADH = Malate → OAA
Conversion of OAA (Matrix)
OAA → Aspartate
Reconversion of Aspartate (Cytosol)
Aspartate → OAA
What is the name of the transporter of lactate outside of the cell?
MCT1
What is the Warburg effect?
Ability of tumors to inhibit the regulators of the rate of glycolytic pathways in order to abnormally increase the rate of glycolysis
What is the side reaction of glycolysis that takes place in red blood cells?
2,3-BPG Shunt
- Draw it
- Forfeits ATP production
What type of hemoglobin regulator is 2,3-Bisphosphoglycerate?
A negative allosteric regulator
What is Cori’s cycle?
Lactate produced by muscles during anaerobic glycolysis is transferred to liver, where it’s converted back to glucose, then transferred back to muscles
This is done to prevent lactate acidosis during intense exercise
Is gluconeogenesis an energy dependent process?
Yes, 6 ATP is used
Which steps of glycolysis are irreversible?
First, last, and third:
- Hexokinase
- Phosphofructokinase (PFK1)
- Phosphokinase
What is different between glycolysis and gluconeogenesis?
The three irreversible enzymes are replaced by enzymes capable of reversing the steps
Which enzyme replaces Hexokinase in gluconeogenesis?
Glucose-6-phosphatase
Which enzyme replaces Phosphofructokinase (PFK1)?
Fructose-1,6-Bisphosphatase
Which enzyme replaces Pyruvate Kinase?
- Pyruvate carboxylase
- Phosphoenolpyruvate (PEP) carboxykinase
What is the pathway of converting pyruvate back to phosphoenolpyruvate?
Pyruvate
to | Pyruvate Carboxylase w/ ATP
Oxaloacetate
to | Phosphoenolpyruvate Carboxykinase w/ GTP
Phosphoenolpyruvate
What cofactor is used with 99% of carboxylases?
Vitamin B7 AKA Biotin
What cofactor is used with most decarboxylases?
Vitamin B6 AKA Pyridoxine
Which step does of gluconeogenesis does not take place in the cytoplasm?
Glucose-6-Phosphate
to | Glucose-6-Phosphatase
Glucose
Takes place in the endoplasmic reticulum
What is the allosteric activator of PFK1?
Fructose-2,6-Bisphoshate formed through PFK2
What are the inhibitors and activators of Hexokinase?
Inhibitors
- Glucose-6-phosphate (negative allosteric)
Activators
N/A
What are the inhibitors and activators of Phosphofructokinase (PFK1)?
Inhibitors
- Citrate
- High ATP
- Low pH (High [H+])
Activators
- High ADP/AMP
- Fructose-2,6-Bisphosphate (positive allosteric)
What are the inhibitors and activators of Pyruvate kinase?
Inhibitors
- High ATP
- High Alanine
- Phosphorylation (Liver)
Activators
- Insulin
- Fructose-1,6-Bisphosphate
What are the inhibitors and activators of Fructose-1,6-Bisphosphatase?
Inhibitors
- High AMP/ADP
- Fructose-2,6-Bisphosphate
Activators
N/A
What are the inhibitors and activators of Pyruvate Carboxylase?
Inhibitors
- N/A
Activators
- Acetyl-CoA
What are the inhibitors and activators of Phosphoenolpyruvate carboxykinase?
Inhibitors
- Insulin
Activators
- Glucagon
What are the inhibitors and activators of Glucokinase?
Inhibitors
- Fructose-6-Phosphate
Activators
- Insulin
- Fructose-1-Phosphate
What are the inhibitors and activators of PFK2?
Kinase part: Insulin (Dephosphorylation)
Phosphatase part: Glucagon (Phosphorylation)
What is the role of epinephrine in the level?
Similar to glucagon
- Activates Protein Kinase A (Phosphorylation)
- LIVER Increase [cAMP]i, inhibiting glycolysis
- LIVER Stimulating gluconeogenesis for muscles
- MUSCLES/HEART Promotes glycolysis
Liver: promote gluconeogenesis (for muscle)
Muscle/Heart: promote glycolysis (for fight-or-flight)
What is the catabolic and anabolic role of Glucagon?
Catabolic
-lysis of everything BUT…
Anabolic
-genesis of glucose (gluconeogenesis)
What is the relationship of alcohol and gluconeogenesis?
Alcohol inhibits gluconeogenesis
