Carbohydrate Metabolism Flashcards
What are the primary results of the pentose phosphate pathway
reduce 2 molecules of NADP+ to NADPH for each glucose-6-P that is oxidatively decarboxylized to ribulose 5-P
Production of ribulose-5-P is used in the synthesis of ______ and some ________
nucleotides, coenzymes
Production of erythrose-4-phosphate is used in the synthesis of ______ ______ ____
aromatic amino acids
What are the three key enzymes in the pentose phosphate pathway
glucose-6-P dehydorgenase, transketolase and transaldolase
What does the oxidative phase of pentose phosphate pathway accomplish for the cell
generates NADPH
what does the nonoxidative phase of the pentose phosphate pathway accomplish for the cell
interconverts C3 - C7 monosaccharides to produce ribulose-5-P for nucleotide synthesis
What is the reaction for the pentose phosphate pathway
6 glucose-6-P + 12NADP+ +6H2O –> 4 fructose-6-P + 2 glyceraldehyde-3-P + 12 NADPH + 12H + 6 CO2
6 ribulose-5-P is converted to 4 fructose-6-P and 2 glyceradlehyde-3-P using _____ _____
carbon shuffle
Reactions in the nonoxidative pathway are catalyzed by what two enzymes
transketolase and transaldolase
Glucose-6-P regenerated from fructose-6-P and g3P by enzymes in _________ pathway
gluconeogenic
Glucose-6-P dehydrogenase activity is allosterically regualated by _____ and ____ ratios
NAD+ and NADPH
When NADP+ is high, what pathway is favoured?
penthose phosphate pathway
when NADPH is high, what pathway is favoured?
glycolysis
G6PD deficiency reduces ability to detoxify oxygen radicals that result from the metabolism of _______ or ______
primaquine or vicine
what is gluconeogenesis
multistep process in which glucose is produced from lactate pyruvate or oxaloacetate from noncarbohydrate sources for export to other tissues
what to plants use gluconeogenesis for
to convert G3P into glucose which is used to make sucrose and starch
How many irreversible steps in gluconeogenesis
3
What are the irreverisble steps in gluconeogenesis
1- converion of PEP via oxaloacetate catalyzed by pyruvate carboxylase
2- dephosphorylation of fructose 1,6 BP by fructose 1,6 BP-1
3- dephosporylation of glucose-6-P by glucose-6, phosphatase
What are the four sources of carbon in glycolysis
lactate, amino acids, glycerol and CO2
What is the overall net reaction of gluconeogenesis
2 pyruvate+2NADH + 4ATP + 2GTP + 2H2O –> glucose + 2NAD + 2H+ + 2ADP + 2GDP + 6Pi
What are the key enzymes in gluconeogenesis
pyruvate carboxylase, phosphoenol pyruvate carboxykinase, FBPase-1, glucose-6-phospotase
T or F: Gluconeogenesis is expensive
T
T or F: Glycolysis and Gluconeogenesis are reciprocally correlated
T
If glycolysis and gluconeogenesis were both allowed to proceed at high rates, what would be the result
a consumption of ATP and GTP and a production of heat
Hexokinase is a _____ enzyme
cytoplasmic
glucose-6-phosphotase is localized in the _____ of the ___
lumen of the ER
_______ transport protein in the plasma membrane of liver cells permits glucose exchange between the inside and outside of the cell
GLUT2
What happens in a low energy environment (High AMP and ADP)
increases flux thoguh stimulation of PFK-1 activity and inhibition of gluconeogenic enzymes pyruvate carboxylase, PEPCK and FBPase-1
What happens in a high energy environment (Metabolites in citric acid cycle accumulate)
stimulates gluconeogenesis by acetyl-CoA and citrate, activates pyruvate carboxylase and FBPase 1
the activity of PFK-1 increases in presence of ___________
fructose 2,6BP
addition of fructose 2,6BP to enzyme reactions containing FBPase1 decreases its affinity for __________
fructose 1,6 BP
Hormonal regulation of glycolysis and gluconeogenesis depends of the phosphoyrlation state of the dualfuction enzyme ____/______
PFK2/FBPase2
What is the Cori Cycle
converts lactase in muscle cells through gluconeogenesis in liver cells, cost of 4 ATP
what is glycogen
a polysaccharide fo glucose that is a storage form of glucose in animals fungi and bacteria
What are the three key reactions in glycogen degredation and synthesis
glycogen phosphorlylase, glycogen synthase, glycogen branching and debranching enzyme
what are the three key reactions for reverisble glycogen degredation and synthesis
1- glycogen phosphorylase releases glucose-1-phosphate from glycogen
2-glycogen synthase adds glucose to nonreducing ends of glycogen
3- glycogen branching and debranching enzymes create multiple nonreducing ends
What does glycogen degredation and synthesis do for animals in the liver
is used as a short term energy source by storing and release glucose in response to blood glucose levels
What does glycogen degredation and synthesis do for animals in the muscles
provides a readily available source of glucose in both anaerobic and aerobic exercise
what is the net reaction for glycogen degredation
glycogen (n units of glucose) + Pi –> glycogen (n-1 units of glucose) + glucose 1 phosphate
what is the net reaction for glycogen synthesis
glycogen (n units of glucose) + glucose 1 phosphate + ATP + H2O –> glycogen (n-1 units of glucose) + ADP + 2 Pi
glycogen phosphorylase catalyzes a phosproylase reaction using the enzyme ___ to generate glucose-1-P
PLP
glycogen synthase catalyzes a reaction using ___-glucose residues one at a time to the nonreducing ends of oxygen
UDP
glycogen binding enzyme creates a new alpha 1,6 branch point and new nonreducing end by transferring __ glucose residues from the end of a growing chain
7
R state conformation of glycogen synthase is __________
unphosphorylated
T state conformation of glycogen synthase is _________
phosphorylated
what leads to the phosphorylation of glycogen synthase
epinephrine and glucagon
Hormonal regulation of glycogen is mediated by phosphorylation and dephosphoylation of _______
glycogen phosphorylase and synthase
