Lecture 21 Flashcards
Direct glucose reserves in the average healthy human are sufficient to meet glucose needs for about how long? what process must you conduct if you must go longer than this length of time?
about 1 day
gluconeogenesis is a process that is important during longer periods of fasting or starvation
State the 3 major precursors for gluconeogenesis. what do these precursor’s all have in common?
Glycerol
AA’s
Lactate
These are all non-carbohydrate precursors
What 2 parts of the body conduct gluconeogenesis and what 2 molecules does the pathway begin and end with?
Gluconeogenesis occurs in the Liver and Kidney
This pathway converts pyruvate into glucose
Gluconeogenesis bypasses the ______ steps of glycolysis (it’s not a reversal of glycolysis). State the 4 enzymes that are NOT present in glycolysis and work together to conduct gluconeogenesis. (include the molecules these act on)
Irreversible
Pyruvate Carboxylase: Pyruvate to Oxaloacetate
Phosphoenolpyruvate carboxykinase: Oxaloacetate to Phosphoenolpyruvate
Fructose-1,6-bisphosphatase: Fructose-1,6-bisphosphate to Fructose-6-phosphate
Glucose-6-phosphatase: Glucose-6-phosphate to Glucose
In gluconeogenesis, state where the 3 ATP/GTP consumption locations are found in this pathway
Pyruvate Carboxylase consumes ATP
Phosphoenolpyruvate carboxykinase consumes GTP
Phosphoglycerate kinase consumes ATP (this occurs between 3-phosphoglycerate and 1,3-bisphosphoglycerate
State which of the 4 Gluconeogenesis-specific enzymes is a mitochondrial enzyme and where they other enzymes are found
Pyruvate carboxylase (PC) is a mito enzyme
Phosphoenolpyruvate carboxykinase, Fructose-1,6-bisphosphatase, and Glucose-6-phosphatase are all found in the cytoplasm
Pyruvate Carboxylase (PC) creates Oxaloacetate in the mitochondria. How is Oxaloacetate transported into the cytoplasm?
Oxaloacetate is transported into the cytoplasm via the “Malate Shuttle”
What form must glucose be in so that it may leave the liver after gluconeogenesis and enter the blood?
It must be “free glucose” (NOT Glucose-6-phosphate)
Where in the cell is glucose-6-phosphatase found? State and describe the function of the T1, T2, and T3 proteins that aid glucose-6-phosphate in it’s creation of free glucose from glucose-6-phosphate.
Glucose-6-phosphatase is found in the lumen of the ER (the T proteins are adjacent to it)
T1: transports glucose-6-phosphate into the ER so that Glucose-6-phosphatase can remove it’s phosphate
T2: transports Inorganic Phosphate back into the cytosol
T3: transports Free glucose back into the cytosol
(T2 and T3 act after the action of Glucose-6-phosphatase)
What determines whether glycolysis or gluconeogenesis will occur?
the energy charge (ATP/ADP ratio)
glycolysis creates ATP while gluconeogenesis consumes ATP
Compare glucagon and insulin in terms of the processes that they favor.
Glucagon favors Gluconeogenesis (decrease ATP/ blood sugar)
Insulin favors Glycolysis (increase ATP/ blood sugar)
For gluconeogenesis and glycolysis regulation in the liver, state the Kinase they activate, and the the enzyme that the kinase activates.
Gluconeogenesis is initiated by glucagon
Activates PKA
PKA stimulates the enzyme FBPase2 (fructose bisphosphatase 2)
Glycolysis is initiated by insulin
Activates Phosphoprotein phosphatase
Phosphoprotein phosphatase stimulates the enzyme PFK2 (phosphofructokinase)
(these both inhibit the other process)
Lactate and pyruvate partake in the cori cycle. Explain the locations these can be found. Include the significance the cori cycle has for pyruvate
Lactate is produced in skeletal muscle and RBC’s
That lactate can then be converted to pyruvate in the liver
Then the pyruvate can enter the gluconeogenic pathway and regenerate glucose
(unlimited power meme)
