30 Questions
What is the primary consequence of excessive fructose ingestion in the liver?
All of the above
What enzyme catalyzes the phosphorylation of galactose?
Galactokinase
Which of the following is NOT a product of galactose metabolism?
Glucose
What is the role of the enzyme UDP-galactose 4-epimerase in galactose metabolism?
It converts UDP-galactose to UDP-glucose
What is the primary consequence of excessive uric acid production due to fructose metabolism?
Hyperuricemia and gout
What is the fate of VLDL produced in the liver due to excessive fructose metabolism?
It is converted to LDL in the circulation
What is the purpose of the red circles in the text?
They indicate allosteric enzymes of the glycolytic pathway
What is the role of aldolase B in the metabolism of fructose?
It cleaves fructose-1-phosphate to D-glyceraldehyde and dihydroxyacetone phosphate
How does the metabolism of fructose differ from the metabolism of glucose?
Fructose metabolism skips the PFK-1 control step in glycolysis
What is the fate of the two triose phosphates (dihydroxyacetone phosphate and glyceraldehyde-3-phosphate) formed from fructose metabolism?
They are degraded through glycolysis
Why is fructose metabolism not affected by fasting or insulin in diabetic patients?
Fructokinase, the enzyme that phosphorylates fructose, is not regulated by glucagon or insulin
What is the consequence of excessive fructose intake along with glucose?
It leads to increased fatty acid and cholesterol synthesis
Which enzyme catalyzes the removal of H2O2 by reduced glutathione?
Glutathione peroxidase
Why is the removal of H2O2 important in erythrocytes?
It prevents oxidative damage to the cell membrane, leading to hemolysis
Which pathway is an alternative oxidative pathway for glucose that does not lead to ATP formation?
Uronic acid pathway
What is the end product of the uronic acid pathway in the liver?
Glucuronic acid and ascorbic acid
Which enzyme catalyzes the reaction that forms UDP-glucuronate in the uronic acid pathway?
UDPGlc dehydrogenase
What is the role of UDPGlc pyrophosphorylase in the uronic acid pathway?
It catalyzes the reaction of glucose-1-P with UTP to form UDPGlc
Which of the following is NOT a function of the pentose phosphate pathway?
Complete oxidation of glucose to CO2
Which enzyme in the pentose phosphate pathway requires the coenzyme thiamin diphosphate (vitamin B1)?
Transketolase
Which of the following tissues is NOT mentioned as having high activity of the pentose phosphate pathway?
Skeletal muscle
What is the primary role of the non-oxidative phase of the pentose phosphate pathway?
Production of ribose-5-phosphate
Which enzyme is required to convert glyceraldehyde-3-phosphate to glucose-6-phosphate in tissues that lack fructose 1,6-bisphosphatase?
This conversion cannot occur in those tissues
What is the role of NADP+ in the pentose phosphate pathway?
It acts as a coenzyme for the oxidative phase
What is the primary manifestation of glucose-6-phosphate dehydrogenase (G6PD) deficiency?
Red blood cell hemolysis (hemolytic anemia)
Which pathway is essential for the regeneration of NADPH in erythrocytes, required for the proper functioning of glutathione peroxidase?
Pentose phosphate pathway
What is the primary function of glutathione peroxidase?
Reduction of organic peroxides and $H_2O_2$
Which vitamin's nutritional status can be assessed by measuring erythrocyte glutathione reductase activity and its activation by FAD?
Vitamin B2 (riboflavin)
Which of the following is a potential consequence of excessive fructose loading in the liver?
All of the above
What is the primary cause of hyperuricemia and gout associated with excessive fructose consumption?
Increased purine synthesis
Test your knowledge on Glucose-6-Phosphate Dehydrogenase (G6PD) and 6-Phosphogluconate Dehydrogenase enzymes, which are NADP-dependent and catalyze irreversible reactions in the Non-oxidative Phase. Learn about their roles in generating ribose precursors for nucleotide and nucleic acid synthesis.
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