Flashcards PHAR 412: Pentose Phosphate Pathway, NADPH and G6PD Deficiency
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Where do the reactions of the pentose phosphate pathway occur in the cell?
In the cytosol.
What are the two branches of the pentose phosphate pathway?
The oxidative branch and the nonoxidative branch.
What is the primary product of the oxidative branch of the pentose phosphate pathway?
NADPH.
What is the physiological significance of ribose 5-phosphate?
It is required for nucleotide synthesis.
How is the pentose phosphate pathway regulated?
Regulation occurs through the availability of substrates and feedback mechanisms.
What are the uses of NADPH in the body?
NADPH is used in biosynthetic reactions, such as fatty acid and cholesterol synthesis.
How does NADPH differ from NADH in terms of function?
NADPH provides reducing equivalents for biosynthetic reactions, while NADH is primarily involved in ATP generation.
What is the role of glutathione in the body?
Glutathione acts as an antioxidant and detoxifies harmful substances.
How is reduced glutathione regenerated?
Using NADPH.
What are the consequences of glucose 6-phosphate dehydrogenase deficiency?
It can lead to hemolytic anemia and increased susceptibility to oxidative stress.
Which vitamins are required for the pentose phosphate pathway?
Folate (B9) is required for nucleotide synthesis.
What is the main function of glycolysis?
To oxidize glucose for energy production.
What is the hexose monophosphate shunt?
Another name for the pentose phosphate pathway.
What does PRPP stand for?
5-phosphoribosyl-1-pyrophosphate.
How is PRPP synthesized?
From 5-phosphoribose, a product of the pentose phosphate pathway.
What is the NADPH:NADP+ ratio in the cytosol?
About 100:1.
What is the role of cytochrome P450 enzymes?
They are involved in drug metabolism and require NADPH.
What happens to glutathione during detoxification?
It is oxidized to form inactive glutathione disulfide (GS-SG).
What factors can deplete glutathione levels?
Poor diet, pollution, toxins, stress, and aging.
What is the significance of the high-level inorganic phosphate in PRPP synthesis?
It upregulates PRPP synthesis.
What is the most critical part of the body's detoxification system?
Glutathione.
What is the primary reaction catalyzed by cytochrome P450?
The insertion of one atom of oxygen into an organic substrate.
What is the relationship between NADPH and fatty acid synthesis?
NADPH provides the reducing equivalents needed for fatty acid synthesis.
How does heavy alcohol consumption affect NADPH levels?
It may severely reduce NADPH in the liver, compromising glutathione activity.
What is the main product of the oxidative phase of the Pentose Phosphate Pathway?
Ribulose 5-phosphate
What byproduct is produced during the oxidative phase of the Pentose Phosphate Pathway?
CO2
How many molecules of NADPH are produced in the oxidative phase?
Two molecules of NADPH
What is the primary function of NADPH in cells?
It acts as a reducing agent.
In which types of cells are high levels of Pentose Phosphate Pathway enzymes found?
Liver cells and rapidly dividing cells.
What is the role of the Pentose Phosphate Pathway in fatty acid synthesis?
It provides NADPH required for the synthesis.
What is the significance of ribose 5-phosphate in the Pentose Phosphate Pathway?
It is required for nucleic acid synthesis.
What is the first step of the oxidative phase in the Pentose Phosphate Pathway?
Conversion of Glucose 6-phosphate.
What is the major alternative pathway for generating NADPH in cells?
The Malic enzyme pathway.
What is the role of the enzyme glucose-6-phosphate dehydrogenase?
It catalyzes the first step in the Pentose Phosphate Pathway.
What is the overall reaction of the Pentose Phosphate Pathway?
Glucose 6-phosphate + 2 NADP+ → Ribulose 5-phosphate + 2 NADPH + CO2.
What is the function of the non-oxidative phase of the Pentose Phosphate Pathway?
It interconverts sugars for nucleotide synthesis.
What is the significance of the Pentose Phosphate Pathway in red blood cells?
It helps regenerate glutathione to protect against oxidative damage.
Which enzyme is responsible for the conversion of ribulose 5-phosphate to ribose 5-phosphate?
Ribose-5-phosphate isomerase.
What are the two main phases of the Pentose Phosphate Pathway?
Oxidative phase and non-oxidative phase.
What type of reaction is catalyzed by transaldolase in the non-oxidative phase?
A transfer of a two-carbon unit between sugars.
What is the primary role of the Pentose Phosphate Pathway in rapidly dividing cells?
To provide ribose 5-phosphate for nucleic acid synthesis.
How do phagocytes utilize NADPH produced in the Pentose Phosphate Pathway?
For the production of superoxide radicals to kill pathogens.
What is the role of NADPH in cytochrome P450 activity?
It provides reducing equivalents for drug metabolism.
What is the relationship between the Pentose Phosphate Pathway and cellular respiration?
It operates parallel to glycolysis and the citric acid cycle.
What is the significance of the oxidative phase of the Pentose Phosphate Pathway?
It generates NADPH and ribulose 5-phosphate.
What is the end product of the oxidative phase of the Pentose Phosphate Pathway?
Ribulose 5-phosphate.
What is the function of the enzyme 6-phosphogluconate dehydrogenase?
It catalyzes the conversion of 6-phosphogluconate to ribulose 5-phosphate.
Why is the Pentose Phosphate Pathway important for detoxification?
It produces NADPH, which is crucial for the regeneration of antioxidants.
What is the role of glucose-6-phosphate in the Pentose Phosphate Pathway?
It is the substrate that initiates the pathway.
What are the six alternative pathways for generating NADPH mentioned?
The pathways include the Pentose Phosphate Pathway and others like the Malic enzyme pathway.