gluconeogenesis Flashcards
brain depends on glucose as its primary fuel and _______ use glucose as their only fuel
red blood cells
whole body needs ______ grams of glucose per day
160
daily glucose requirement of brain
120 grams
glucose present in body fluids
20 grams
glucose readily available from glycogen
190 grams
direct glucose reserves are sufficient to meet glucose needs for about _____
1 day
gluconeogenesis is especially important during a longer period of
fasting or starvation
where does gluconeogenesis occur
liver and kidney
gluconeogenesis is the synthesis of glucose from
non-carbohydrate precursors
glucogenesis converts _______ into _______
pyruvate
glucose
major precursors of gluconeogenesis
lactate, amino acids, and glycerol
pyruvate carboxylase (PC) is a ________ enzyme
mitochondrial
other enzymes (besides PC) of gluconeogenesis is found in
cytoplasm
oxaloacetate (OAA), a product of PC, is transported to cytoplasm via
malate shuttle
rate-limiting step of gluconeogenesis
F1,6-BP –> F6P via fructose 1,6-bisphosphatase
free glucose from gluconeogenesis can leave _____ and enter ______
liver
blood
glucose 6-phosphatase is a gluconeogenesis enzyme located where
in the lumen of the ER
a protein called ______ transports glucose 6-phosphate to ER
T1
a protein called ______ transports inorganic phosphate back into cytosol
T2
a protein called ______ transports glucose back to cytoplasm
T3
gluconeogenesis “by-passes” the irreversible steps of glycolysis through 4 enzymes not present in glycolysis
pyruvate carboxylase
phosphoenolpyruvate carboxykinase (PEP carboxykinase)
Fructose 1,6-bisphosphatase
glucose 6-phosphatase
gluconeogenesis makes ______ , it requires ______
glucose
ATP
gluconeogenesis has ______ points of ATP/GTP consumption
3
in glycolysis, what activates the rate limiting step (activates PFK)?
F-2,6-BP
AMP
in glycolysis, what inhibits the rate limiting step (inhibits PFK)?
ATP
citrate
H+
in gluconeogenesis, what activates the rate limiting step (fructose 1,6-bisphosphatase)?
citrate
in gluconeogenesis, what inhibits the rate limiting step (fructose 1,6-bisphosphatase)?
F-2,6-BP
AMP
in glycolysis, what activates pyruvate kinase?
F-1,6-BP
in glycolysis, what inhibits pyruvate kinase?
ATP
alanine
in gluconeogenesis, what activates pyruvate carboxylase?
acetyl CoA
in gluconeogenesis, what inhibits pyruvate carboxylase
ADP
in gluconeogenesis what inhibits phosphoenolpyruvate carboxykinase
ADP
gluconeogenesis is favored when
blood glucose levels are low and glycogen stores are depleted
glycolysis energy
use
yield
net yield
use: 2 ATP
yield: 4 ATP
net yield: 2 ATP/glucose oxidized
gluconeogenesis energy
use
yield
net yield
use: 4 ATP, 2 GTP
yield: 0
net yield: 6 ATP equivalents/glucose synthesized
insulin always stimulates a
phosphatase
glucagon always stimulates a
kinase
insulin stimulates phosphoprotein phosphatase –> ______ is activated –> ______ is stimulated and ______ is inhibited
PFK2
glycolysis
glucogenogenesis
glucagon stimulates protein kinase A (PKA) –> ______ is activated –> ______ is inhibited and ______ is activated
fructose bisphosophatase 2 (FBPase2)
glycolysis
gluconeogenesis
the concentration of fructose 2,6-BP, a signaling molecule that stimulates or inhibits glycolysis is controlled by a fi-functional enzyme with a kinase and phosphatase domains
phosphofructokinase 2 (PFK2) and fructose bisphosphatase 2 (FBPase2)
the cori cycle:
lactate produced in skeletal muscle and red blood cells can be converted back to:
the pyruvate can enter the gluconeogenic pathway and regenerate:
pyruvate in the liver
glucose (which was the source of the lactate)
