Glycolysis Flashcards
3 Key Regulatory Enzymes in Gycolyisis
Hexokinase (Galactokinase in LIVER)
Phosphofrucktokinase-1 (PFK1)
Pyruvate Kinase
Hexokinase Function
Phosphorylates GLUCOSE to Glucose-6-Phosphate (G6P) = IRREVERSIBLE HAVE VERY - Free Energy Change
Uses ATP to do so (INVESTMENT)
Substrate Level Phosphorylation
Hexokinase Regulation
Product Inhibition by Glucose-6-Phosphate
Phosphofrucktokinase-1 Function
Converts FRUCTOSE-6-PHOSPHATE to FRUCTOSE-1,6-BISPHOSPHATE
IRREVERSIBLE SIINCE VERY NEGATIVE FREE ENERGY CHANGE
The Committing Step
Why is the step involving enzyme Phosphofrucktokinase called the COMMITTING STEP?
It means the glucose is committed to metabolism via glycolysis
SInce the Fructose-6-Phosphate can be converted back into Glucose-6-Phosphate which can enter the Pentose Phosphate Pathway
Once Fructose-1,6-Bisphosphate has been made its irreversible and can’t be converted back to Fructose-6-Phosphate so glucose has to follow glycolysis pathway
Phosphofrucktokinase-1 2 Types of Regulation
Alosteric Regualtion
Covalent Modification (phosphorylation)
Phosphofrucktokinase Allosteric Regualtion
STIMULATED by Low Energy signals (More glycolysis needed):
-AMP
INHIBITED by:
-High ATP (less glycolysis needed)
-Citrate
Phosphofrucktokinase Hormonal Regulation:
SIMULATED by INSULIN (Wants to get glucose levels as low as possible)
INHIBITED by GLUCAGON (Wants to keep blood glucose as high as possible)
The ATP:AMP Ratio Affects Phosphofrucktokinase activity
High ATP:AMP ratio INHIBITS. Phosphofrucktokinases
Low ATP:AMP ratio stimulates Phosphofrucktokinase
Pyruvate Kinase Function
Converts Phospoenolpyruvate to Pyruvate
Irreversible since very negative Free Energy Change
Pyruvate Kinase Regulation
High Insulin:Glucagon ratio stimulates
Low Insulin:GLucagon ratio inhibits
When is Lactate Production Important for Glycolysis
When the cell has no:
-Oxygen access
-Or available mitochondria
Why is Lactate/Lactic acid Production IMportant for anaerobic glycolysis?
Cell Unable to regenerate REDUCING POWER (NAD+)
Oxidative phosphorylation can’t happen to regenerate NAD+ from NADH
No NAD+ means Glycolysis ceases
Enzyme the converts Pyruvate Into Lactate is called
Lactate Dehydrogenase (LDH)
What does Lactate Dehydrogenase ACTUALLY do
Allows NADH to add a H to a pyruvate molecule reducing the pyruvate to LACTATE and leaving behind NAD+
