Gluconeogenesis and glucose homeostasis Flashcards
When does gluconeogenesis occur
- exercise (lactate)
- short term fasting (alanine)
- Diabetes (insulin sensitivity)
- Trauma (peripheral insulin resistance)
What noncarbohydrate precursors does gluconeogenesis use to make glucose
- lactate
- Amino acids (alanine)
- Glycerol (triacylglycerols)
Where does gluconeogenesis occur
liver
kidney
small intestine
Which part of the cell does gluconeogenesis occur
CYtosol
How does gluconeogenesis occur
Same as glycolysis apart from 3 steps;
- pyruvate to PEP
- F1,6 BP to F6P
- G6P to glucose
What does pyruvate get turned into and and what does this get turned into
Pyruvate —oxaloacetate—-PEP
Why is the malate shuttle used
Used because oxaloacetate can’t get out of mitochondria to cytosol so needs to get converted to malate. Malate then leaves mitochondria via malate shuttle then gets converted to oxaloacetate again
How many carbons is pyruvate and how many carbons is oxaloacetate
3
4
What enzyme turns pyruvate to oxaloacetate
pyruvate carboxylase
What is needed to turn pyruvate to oxaloacetate and what is the by-product
needs; Co2 and ATP
produces; ADP+ Pi
Where is pyruvate carboxylase found
mitochondrion
To turn oxaloacetate to malate and back to oxaloacetate, what is needed
-REDOX of NADH
To turn oxaloacetate to PEP, what enzyme is needed
PEP carboxykinase
What is needed to turn oxaloacetate to PEP and what are the by-products
needs; GTP
by products; GDP + Co2
What does pyruvate carboxylase catalyse and where is it found
Glucose to pyruvate
-found in all tissues
Why is pyruvate carboxylase found in all tissues
There’s a need to replenish oxaloacetate for example in the TCA cycle (as pyruvate produces oxaloacetate)
What then happens to PEP?
gets converted to Fructose 1,6 bisphosphate
What happens to fructose 1,6 bisphosphate and why is this an important reaction
Gets turned to fructose 6 phosphate by FRUCTASE 1,6 BISPHOSPHATASE
-tightly regulated
What happens to fructose 6 phosphate
Gets turned to glucose 6 phosphate by phosphoglucose isomerase
What happens to Glucose 6 phosphate
Gets turned to glucose by glucose 6 phosphatase (removes phosphate group so glucose can move out of cell)
When does gluconeogenesis occur (i.e. glucose and ATP levels )
- glucose levels are low
- ATP levels are high
How are reciprocal regulation of gluoneogeneis and glycolysis affected
Allosterically
What is gluconeogenesis regulated by hormonally
Insulin
Glucagon
Role of insulin in regulation
- promotes synthesis of glycolytic enzymes PFK, PK, PFK2
- inhibits synthesis of PEPCK
Role of glucagon in regulation
-Increase expression of PEPCK and F1,6BPase
What is the Cori Cycle
Glycolysis in muscle;
- glucose to pyruvate then lactate
- lactate goes into blood and then to liver
Gluconeogenesis in liver;
- lactate from muscle gets converted to pyruvate and then to glucose
- glucose goes to blood and then back to the muscle
How are amino acids used as gluconeogenic precursors
- Remoce amino groups
- Carbon skeletons can be converted to glucose
