MCB Lecture 12 Pyruvate Fate, Cancer, Gluconeogenesis, Cori Cycle Flashcards
Describe the process of fermentation
Pyruvate -> Acetaldehyde (ethanal) -> Ethanol
What happens to pyruvate in yeast?
Fermentation : –> Ethanol produced
Which enzymes are involved in fermentation?
Pyruvate decarboxylase (pyruvate -> Acetaldehyde)
Alcohol dehydrogenase (Acetaldehyde -> ethanol) NADH -> NAD+
What is the fate of pyruvate in anaerobic conditions? Why?
Lactate, to regenerate the NAD+
Outline the steps in anaerobic glycolysis
Pyruvate -> L-lactate
Lactate dehydrogenase
NADH -> NAD+
What is important about glycolysis in terms of tumour detection?
Tumours have reduced vascularisation and increased rates of glycolysis because they are growing and dividing rapidly.
Using isotopically marked glucose we can track it to the tumour using PET scanning
What is the significance of glycolysis in terms of cancer treatment?
Chemotheraputic agents target hexokinase.
Without this enzyme, the first step of glycolysis cannot occur.
This halts the energy supply to the tumour.
Describe the overall reaction of gluconeogenesis
This is converting pyruvate back to Glucose.
It is not simply the reversal of glycolysis.
There are three steps in glycolysis that are irreversible, and when we want to do the reverse reaction, we must employ a different enzyme.
What are the irreversible steps of glycolysis?
Glucose -> glucose-6-phosphate
Fructose-6-phosphate -> Fructose-1,6-phosphate
Phosphoenolpyruvate -> pyruvate
What enzyme is used for converting pyruvate? Give the steps
Pyruvate -> oxaloacetate
Pyruvate carboxylate
Oxaloacetate -> phosphoenolpyruvate
PEP carboxykinase
What enzyme is used to convert fructose-1,6-bisphosphate?
Fructose-1,6-phosphate -> Fructose-6-phosphate
Fructose-1,6-phosphatase
What enzyme is used to convert glucose-6-phosphate?
Glucose-6-phosphate -> glucose
Glucose-6-phosphatase
Where does conversion glucose-6-phosphate -> glucose occur?
In the lumen of the ER in the Kidney and hepatocytes of the liver
Glucose-6-phosphatase is embedded in the inner membrane of the ER
Describe the cori cycle in terms of molecules, areas in the body and when this cycle occurs
When you are exercising vigorously, and you don’t have enough oxygen getting to your cells, you breakdown glucose anaerobic ally in the muscles.
Glucose -> L-lactate (muscles)
Lactate gets transported via the blood to the liver where it is converted to glucose
Lactate -> Glucose (liver)
Glucose is transported back into the blood and delivered to the muscles
What happens to cytosolic NADH under aerobic conditions?
- Malate-Aspartate shuffle
2. Glycerol-3-Phosphate shuffle
