Glycolysis Flashcards
What is the preferred energy source for the brain in non-starvation conditions?
Glycolysis
What is a crucial source of energy in anaerobic conditions?
Glycolysis
What are the two general phases of glyclysis?
Energy investment
Energy production
What are the general products of glycolysis?
ATP
NADH
Pyruvate - lactate
What are the enzymes of the three irreversible reactions of glycolysis?
Hexokinase/glucokinase
PFK-1
Pyruvate kinase
What are the metabolic pathways that G6P can be used for?
Glycolysis
Pentose phosphate pathway
Uronic acid pathway
Glycogenesis
Out of hexokinase and glucokinase, what is inhibited by G6P?
Hexokinase
What is caused by a hexokinase deficiency?
Hemolytic anemia
What is the most important site of regulation in the glycolysis pathway?
PFK-1
What are the priming reactions of glycolysis and what does that mean?
Catalyzed by hexokinase/glucokinase and PFK-1
Energy used
What will occur with a PFK-1 deficiency?
Hemolytic anemia
What cells lack mitochondria and perform anaerobic glycolysis?
RBCs
What happens to NADH produced in glycolysis?
Has to be recycled, different pathways
What does the fate of pyruvate produced by glycolysis depend on?
The availability of oxygen
What happens to pyruvate in anaerobic conditions?
Reduced by lactate dehydrogenase to lactate using NADH to NAD+
What are the tissues that typically produce lactate?
Skeletal muscle
RBCs
Brain
GI tract
Renal medulla
Retina
Skin
Where is lactate usually taken up and oxidized?
Liver
Kidneys
Heart
How much ATP is produced from glycolysis in anaerobic conditions?
Net 2 ATP
How much ATP is produced from glycolysis in aerobic conditions?
Net 7 ATP
What are the two ATP producing enzymes of glycolysis?
Phosphoglycerate kinase
Pyruvate kinase
What enzyme of glycolysis produces NADH?
Glyceraldehyde 3-phosphate dehydrogenase
What sugars can be oxidized via glycolysis?
Fructose
Galactose
Mannose
Glycerol
What allows the unloading of oxygen in RBCs?
RL shunt
What enzyme and reaction is bypassed in the RL shunt in RBCs?
Phosphoglycerate kinase
What is provided by RL shunt to decrease Hgb affinity for oxygen?
2,3-bisphosphoglycerate
What Hgb exhibits a lower affinity for 2,3-bisphosphoglycerate?
Fetal Hgb
What is the result of pyruvate kinase deficiency?
Hemolytic anemia
What deficiency would the presence of Heinz bodies indicate?
G6PD deficiency
With what glycolytic enzyme deficiency would you see an increase in 2,3-bisphosphoglycerate?
PK deficiency
What are clinical signs of pyruvate kinase deficiency?
Anemia
Growth delay
Failure to thrive
Jaundice
Mild-moderate splenomegaly
What is lactic acidosis?
State of acidosis characterized by elevated plasma lactate concentration
What causes lactic acidosis?
Circulatory insufficiency
Severe anemia
Inhibitors (carbon monoxide, cyanide)
Alcohol
PDH complex deficiency
Severe exercise
Von Gierke’s disease
How does fluoride inhibit glycolysis?
Inhibits enolase
How does fluoride work in oral cavity to prevent cavities?
Inhibiting bacterial glycolysis
What enzymes are infected in general by arsenic?
-SH group containing enzymes
How does arsenate affect glycolysis?
Interfere with glyceraldehyde-3P dehydrogenase decreasing ATP and NADH production - competes with phosphate
Does not inhibit pathway
How does iodoacetate inhibit glycolysis?
Inhibits glyceraldehyde 3P dehydrogenase
How does bromohydroxyacetone phosphate inhibit glycolysis?
Inhibits dihydroxyacetone phosphate
How does oxamate inhibit glycolysis?
Inhibits lactate dehydrogenase
How will the rate of glycolysis respond to hyperglycemia?
Increase
How will the rate of glycolysis respond to the presence of insulin in the blood stream?
Increase
How will the rate of glycolysis respond to hypoglycemia?
Decrease
How will the rate of glycolysis response to glucagon in the blood stream?
Decrease
What induces the transcription of the rate limiting enzymes of glycolysis?
Insulin
What represses the transcription of the rate limiting enzymes of glycolysis?
Glucagon
How does G6P affect hexokinase and glucokinase?
Inhibits hexokinase
Does not inhibit glucokinase
How does ATP affect PFK-1?
Allosteric inhibitor
How does AMP affect PFK-1?
Reverses affect of ATP at high concentrations
How does citrate regulate glycolysis?
Inhibits PFK-1
How does fructose-2,6-bisphosphate affect glycolysis?
Allosteric activator of PFK-1
Inhibits fructose-1,6-bisphosphatase
What activates PK?
AMP
Fructose-1,6-bisphosphate
What inhibits PK?
ATP
Acetyl CoA
Alanine
How does covalent modification in the liver affect PK?
Phosphorylated PK is more strongly inhibited by ATP and alanine
What is the Warburg Effect?
Lactate produced in presence of oxygen in tumors and other proliferating cells
