Glycolysis, Gluconeogenesis and Pentose Phosphate Pathway Flashcards
Which glucose transporter is insulin sensitive?
GLUT 4
Where is GLUT 4 found?
Muscle and adipose tissue
Where is GLUT 1 found?
Erythrocytes
Endothelial tissue
(Muscle and adipose tissue also)
Where is GLUT 2 found?
Liver and pancreas
Where is GLUT 3 found?
Brain
Where is GLUT 5 found?
Intestines and kidney
What reactions occur in glycolysis and in the correct order?
Phosphoryl transfer
Phosphoryl shift
Isomerisation
Dehydration
Aldol cleavage
Which intermediate gets split in 2?
Fructose-1,6-bisphosphate
List, in order, the intermediates in the investment phase of glycolysis?
Glucose
Glucose-6-phosphate
Fructose-6-phosphate
Fructose-1,6-bisphosphate
Glyceraldehyde-3-phosphate & Dihydroxyacetone phosphate
List, in order, the enzymes in the investment phase of glycolysis?
Hexokinase
Phosphohexose isomerase
Phospho fructose kinase-1
Aldolase
Triose phosphate isomerase
List, in order, the intermediates in the payoff phase of glycolysis.
Glyceraldehyde-3-phosphate
1,3-bisphosphoglycerate
3-phosphoglycerate
2-phosphoglycerate
Phosphoenolpyruvate
Pyruvate
List, in order, the enzymes in the payoff phase of glycolysis?
Glyceraldehyde-3-phosphate dehydrogenase
Phosphoglycerate kinase
Phosphoglycerate mutase
Enolase
Pyruvate kinase
What are the enzymes that catalyse irreversible reactions in glycolysis?
Hexokinase
Phosphofructose kinase 1
Pyruvate kinase
Which enzymes require the hydrolysis of ATP to complete their functions?
Hexokinase
Phosphofructose kinase 1
Which step produces NADH in glycolysis?
Conversion of glyceraldehyde-3-phopshate to 1,3-bisphosphoglycerate by using glyceraldehyde-3-phosphate dehydrogenase
Which steps produce ATP?
Conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate by using phosphoglycerate kinase
Conversion of phosphoenolpyruvate to pyruvate by using pyruvate kinase
Which enzyme is highly regulated in this pathway?
Pyruvate kinase
What is used as a coenzyme during the phosphorylation of glucose?
Mg++
Where is the only place that phosphorylation of glucose is reversible?
Liver
What is the purpose of phosphorylating glucose?
Lowers intracellular glucose concentration allowing further uptake of glucose
What is the primary inhibitor of phosphofructose kinase 1?
High ATP concentrations
What is the fate of fructose-6-phosphate if PFK1 is inactivated?
Will be stored as glycogen
What intermediates does frucotse-1,6-bisphosphate produce?
Dihydroxyacetone phosphate and glyceraldehyde-3-phosphate
Which of the intermediates that fructose-1,6-bisphosphate produces is unable to continue on the glycolysis pathway?
Dihydroxyacetone phosphate
Why is the glyceraldehyde-3-phosphate concentration kept low?
To pull the reaction forward along the pathway
What does the production of NADH from the oxidation of glyceraldehyde-3-phosphate by glyceraldehyde-3-phosphate dehydrogenase do?
Allows for net production of ATP
What is the oxidation of glyceraldehyde-3-phosphate coupled to?
1st production of ATP by phosphoglycerate kinase
What coenzymes regulate the activity of pyruvate kinase?
K+ and Mg++
What is consumed during the entirety of glycolysis?
1 glucose
2 ATP
2 NAD+
What is produced by glycolysis?
2 pyruvate
4 ATP
2 NADH
What cleaves glucose from glycogen and starch?
Glycogen phosphorylase
What does the cleaving of glucose from glycogen yield?
Glucose-1-phosphate
What is the main source of energy in fast twitch muscle fibers?
GLycolysis
What does LDH do during anaerobic conditions?
Regenerates NAD+ stores
What is a by-product of glycolysis in RBCs?
2,3-diphosphoglycerate
Under what conditions do 2,3-diphosphoglycerate concentrations increase?
Hypoxic environments
What does 2,3-diphosphoglycerate do?
Promotes release of O2 to tissue when O2 tension and saturation is decreased in lungs
What is faster: tumour growth or angiogenesis?
Tumour growth
What does the growth of tumours mean in terms of their respiration?
Mostly glycolytic respiration resulting in raised LDH levels
Which enzymes regulate the glycolysis pathway?
Hexokinase
Phosphofructose kinase 1
Pyruvate kinase
Can mammals convert fatty acids to sugars?
No
Where does gluconeogenesis occur?
Cytosol of liver cells
Is ATP generated during gluconeogensis?
No
Why is gluconeogenesis differentially regulated?
to prevent a futile cycle
Which enzymes are unique to gluconeogensis?
Pyruvate carboxylase
Phosphoenolpyruvate carboxykinase
Fructose-1,6-bisphosphatase 1
Glucose 6 phosphatase
Where is pyruvate carboxylase found?
Matrix of mitochondria
How does oxaloacetate leave the mitochondria?
Converted to PEP or malate
How is fructose-1,6-bisphosphatase regulated?
By Phosphofructose kinase 1
Where is glucose 6 phosphatase found?
Endoplasmic reticulum
What does gluconeogenesis require?
4 ATP
2 GTP
2 NADH
When does gluconeogenesis generate glucose?
During starvation
Vigorous execise
Explain the Cori Cycle.
Glucose gets converted to lactate in muscle
Lactate gets converted to glucose in liver
What is the role of the Cori Cycle?
Frees muscle from burden of having to produce more energy
What is the role of the pentose phosphate pathway?
Formation of pentose phosphate for synthesis of nucleotides
What happens to excess pentoses?
Shunted back to glycolysis by conversion to fructose-6-phosphate and glyceraldehyde-3-phosphate
Which cells benefit from the pentose phosphate pathway the most?
Cells in which there’s a limited need for RNA/DNA synthesis
What are the main products of the pentose phosphate pathway?
NADPH and ribose-5-phosphate
What are the functions of NADPH?
Electron donor
Biosynthesis of fatty acids, cholesterol and steroids
Repair of oxidative damage
What are the functions of ribose-5-phosphate?
Precursor of nucleotides
DNA & RNA synthesis
Synthesis of some coenzymes
What does the liver use NADPH for?
Hydroxylation(detoxification and excretion of drugs)
What is glutathione?
Coenzyme for the protection of the cell against oxidative and chemical insult
Where is there more NADPH than ribose-5-phosphate?
Liver and adipose tissue
What regulates partitioning into glycolysis versus pentose phosphate pathway?
NADPH (also an antagonist of the system)
When can glucose-6-phosphate dehydrogenase be fatal?
During oxidative stress
How is glucose-6-phosphate dehydrogenase fatal during oxidative stress?
Impairs NADPH production resulting in haemolysis and creates Heinz bodies in erythrocytes
