What is gluconeogenesis?
The synthesis of glucose from simpler precursors like pyruvate and lactate.
Which tissues rely heavily on glucose?
Brain, erythrocytes, kidneys, embryonic tissues.
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What is gluconeogenesis?
The synthesis of glucose from simpler precursors like pyruvate and lactate.
Which tissues rely heavily on glucose?
Brain, erythrocytes, kidneys, embryonic tissues.
Where does gluconeogenesis primarily occur in mammals?
In the liver.
How many glycolysis enzymes are shared by gluconeogenesis?
Seven out of ten.
How does gluconeogenesis bypass the three irreversible steps of glycolysis?
By using energetically favorable reactions.
What is the main energy source for the brain?
Glucose
What is the key precursor molecule for gluconeogenesis?
Pyruvate
Which enzyme converts pyruvate to oxaloacetate?
Pyruvate carboxylase.
Why can't oxaloacetate be directly transported from mitochondria to the cytosol?
Mitochondria lack an oxaloacetate transporter.
Which enzyme converts malate back to oxaloacetate in the cytosol?
Malate dehydrogenase.
What is the first bypass in gluconeogenesis?
Conversion of pyruvate to phosphoenolpyruvate (PEP) via oxaloacetate.
Which amino acids are glucogenic?
Amino acids that can be converted into glucose via the citric acid cycle.
Can mammals convert fatty acids to glucose?
No, except for glycerol.
What is reciprocal regulation?
The mechanism that prevents glycolysis and gluconeogenesis from occurring simultaneously.
What pathway allows plants and microorganisms to convert fatty acids to glucose?
The glyoxylate pathway.
Which enzymes are involved in the reciprocal regulation of glycolysis and gluconeogenesis?
Phosphofructokinase-1 (PFK-1) and fructose 1,6-bisphosphatase (FBPase-1).
Which hexokinase is not inhibited by glucose-6-phosphate?
Hexokinase IV (glucokinase).
Where is glucokinase primarily found?
Liver, pancreas, hypothalamus, and small intestine.
How does ATP affect phosphofructokinase-1 (PFK-1)?
ATP inhibits PFK-1 by binding to an allosteric site.
What molecule relieves ATP inhibition of PFK-1?
AMP and ADP
What is the role of citrate in regulating glycolysis?
Citrate inhibits PFK-1, signaling that the cell's energy needs are being met.
What does high AMP inhibit in gluconeogenesis?
Fructose bisphosphatase-1 (FBPase-1).
What signals low blood glucose levels to stimulate gluconeogenesis?
Glucagon.
What does insulin do to gluconeogenesis?
Inhibits it.
What happens to blood glucose levels in diabetes mellitus?
They are elevated.
Which type of diabetes involves autoimmune destruction of pancreatic beta cells?
Type 1 diabetes.
Which gene is the strongest genetic risk factor for Type 2 diabetes?
TCF7L2 gene.
What is hemoglobin A1c (HbA1c)?
A measure of blood glucose control over a period of 120 days.
What happens when acetyl-CoA accumulates from fatty acid breakdown?
It signals to stop glucose oxidation and stimulates gluconeogenesis.
What hormone promotes glucose uptake and storage in cells?
Insulin.
What is the effect of fructose 2,6-bisphosphate on PFK-1?
It increases PFK-1's affinity for fructose 6-phosphate.
What is the effect of fructose 2,6-bisphosphate on FBPase-1?
It reduces FBPase-1’s affinity for its substrate.
How does glucagon affect fructose 2,6-bisphosphate levels?
Glucagon lowers its levels, inhibiting glycolysis and stimulating gluconeogenesis.
How does insulin affect fructose 2,6-bisphosphate levels?
Insulin increases its levels, stimulating glycolysis and inhibiting gluconeogenesis.
What is the main hormonal signal for gluconeogenesis during fasting?
Glucagon.
How many bypass reactions occur in gluconeogenesis?
Three.
Why is gluconeogenesis considered energetically expensive?
It requires a significant input of ATP and GTP to convert pyruvate to glucose.
Which enzyme converts pyruvate to phosphoenolpyruvate (PEP)?
Phosphoenolpyruvate carboxykinase (PEPCK).
Which tissues cannot utilize fats for energy and depend on glucose?
Brain and erythrocytes.
What is the role of pyruvate carboxylase in gluconeogenesis?
It catalyzes the conversion of pyruvate to oxaloacetate
Which molecule allosterically stimulates pyruvate carboxylase?
Acetyl-CoA.
How does high ATP affect gluconeogenesis?
It stimulates gluconeogenesis by slowing down glycolysis.
What is the effect of insulin on gluconeogenesis-related gene transcription?
Insulin regulates the transcription of more than 150 genes related to gluconeogenesis.
What can diabetic ketoacidosis result from?
Insufficient insulin, causing the body to break down fats and produce ketones.
What is the function of glucose 6-phosphatase in gluconeogenesis?
It catalyzes the final step, converting glucose 6-phosphate to free glucose.
Which molecule is an indicator of low energy levels in the cell?
AMP.
How does acetyl-CoA affect pyruvate dehydrogenase?
It allosterically inhibits pyruvate dehydrogenase, reducing glucose oxidation.
What is the role of metformin in Type 2 diabetes treatment?
It lowers blood glucose by reducing gluconeogenesis in the liver.
What is the consequence of high blood glucose in diabetes mellitus?
Damage to blood vessels and tissues, potentially leading to complications like kidney failure or blindness
What does insulin promote besides glucose uptake?
Glycogen storage and fat synthesis.