Flashcards in Part 2 - lecture 1.3 - Quiz Deck (23):
Why do we need gluconeogensis?
Certain cells like the brain, RBCs, kidney mellula, testis, and eye cells rely on glucose for energy
Which organ(s) are capable of gluconeogenesis?
90% liver, 10% kidney
Which hormone signals to start and which to stop gluconeogenesis? And what signals for this hormone secretion
Glucagon - start
Insulin - stop
Signaled by glucose
What are the various substrates for gluconeogenesis?
Glycerol from triglyceride breakdown
OOA from odd carbon FA chains in beta oxidation and AA
Lactate from the Cori cycle for glycolysis in other tissues
Alanine from pyruvate
What is the Cori cycle?
When peripheral tissues use ATP to produce lactate and send to the liver to produce glucose to send back out into the periphery
What is the alanine cycle?
When skeletal muscle releases AA such as alanine from proteins to be used for glucose production in times of need that are sent to the liver - ammonia removed in form of urea - ATP dependent
What is used instead of pyruvate kinase in gluconeogenesis?
2 step process that uses pyruvate carboxylase (biotin dependent and resides in mitochondria) to form OOA (ATP dependent) - OAA can't be brought out of mitochondria so it uses the shuttle system with NADH to form Malate which goes out into cytosol to be converted back to OAA which uses PEP carboxykinase with GTP to form PEP
What is the overall energy reaction of gluconeogenesis?
2 lactate + 6 ATP + 6 H20 --> glucose + 6 ADP + 6 Pi
What is a reaction that forms intermediates of a metabolic pathway and what is an example?
Anaplerotic reaction - pyruvate to OOA
What is the enzyme used in place of PFK1?
F16bisphosphatase to form F6P
What enzyme is used in place of hexokinase and where is it located?
G6phosphatase located in ER - G6P is moved from cytosol to ER by translocase
What transports glucose and inorganic phosphate out of ER to cytosol and to the blood stream?
GLUT-7 to cytosol and GLUT-2 to blood stream
Why is the liver special?
It has GLUT2 on cell surface and releases glucose derived from glycogen and gluconeogensis
Which AA can not participate in glucose synthesis
Leucine and Lysine - they are ketogenic
How do FAs and glycerol contribute to glucose synthesis?
Triglycerides from adipose storage can be hydrolyzed to get glycerol which can be converted into DHAP to produce a 1/2 glucose
FA beta oxidation occurs in odd carbon FAs that produce AcCoA units to also give 1/2 glucose
Can ketones form glucose?
No because ketones can't be converted into pyruvate or OOA
Can glucose be synthesized from other sugars?
Yes, when liberated from complex carbs can be used in gluconeogenesis in the liver (mannose and galactose)
What can stimulate pyruvate carboxylase?
acetyl CoA upregulated by FA beta oxidation
What can induce synthesis of PEP carboxykinase?
What can inhibit F16BP and activate it?
Glucagon stimulates while AMP and F26BP inhibit
What does increased glucagon do in gluconeogenesis?
Increased FA beta oxidation to increase AcCoA to upregulate pyruvate carboxylase
Down regulate pyruvate kinase and F26BP (decreasing PFK1 by inhibition of PFK2) to stop glycolysis
What does increased insulin do in gluconeogensis?
Stimulates glycolysis by increasing F26BP levels from restoration of kinase activity of PFK2 to produce PFK1