Hexose Monophosphate Shunt Pathway Quiz

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Questions and Answers

What is the main aim of the uronic acid pathway?

  • Production of glucose
  • Synthesis of glucuronic acid (correct)
  • Conversion to uridine triphosphate
  • Generation of free radicals

Which form of glucose is produced in the uronic acid pathway?

  • Glucuronic acid
  • Fructose 6-phosphate
  • Glucose 6-phosphate
  • UDP-glucose (correct)

What is the end product of glucuronic acid metabolism in humans?

  • Glyceraldehyde 3-phosphate
  • D-xylulose 5-phosphate (correct)
  • Fructose 1,6-bisphosphate
  • Glucose 6-phosphate

How does glucuronic acid contribute to detoxification?

<p>By conjugating with agents for excretion (A)</p> Signup and view all the answers

Why is bilirubin mentioned in relation to the importance of the uronic acid pathway?

<p>To facilitate the excretion and prevent jaundice (C)</p> Signup and view all the answers

What is the main role of the Cytochrome P450 mono-oxygenase system in the human body?

<p>Detoxifying harmful agents like drugs and food preservatives (C)</p> Signup and view all the answers

In the Cytochrome P450 monooxygenase system, what provides the reducing equivalents (hydrogen) required for the series of reactions?

<p>NADPH (B)</p> Signup and view all the answers

Which enzyme deficiency is characterized by hemolytic anemia due to the inability to detoxify oxidizing agents?

<p>G6PD deficiency (B)</p> Signup and view all the answers

Aside from hemolytic anemia, what is another clinical manifestation of G6PD deficiency that typically appears 1–4 days after birth?

<p>Neonatal jaundice (A)</p> Signup and view all the answers

What resistance effect does G6PD deficiency share with Sickle cell trait and thalassemias?

<p>Resistance to malaria (D)</p> Signup and view all the answers

Which pathway is a parallel pathway to glycolysis and converts glucose 6-phosphate to fructose 6-phosphate and glyceraldehyde 3-phosphate?

<p>Hexose monophosphate shunt (A)</p> Signup and view all the answers

What is the primary product generated from the conversion of glucose 6-phosphate in the Hexose monophosphate shunt?

<p>Ribose 5-phosphate (A)</p> Signup and view all the answers

Which molecule is crucial for maintaining the integrity of the red blood cell membrane?

<p>NADPH (A)</p> Signup and view all the answers

Which metabolic pathway is essential for detoxifying bilirubin released during hemoglobin breakdown?

<p>Glucuronic acid pathway (C)</p> Signup and view all the answers

What is the main function of the Hexose monophosphate shunt in the context of red blood cells?

<p>Generation of NADPH (C)</p> Signup and view all the answers

What is the role of glutathione peroxidase in the detoxification process?

<p>It reduces H2O2 to water in the presence of reduced glutathione. (B)</p> Signup and view all the answers

What is the function of NADPH in the detoxification process related to hydrogen peroxide?

<p>It regenerates GSH through a reaction catalyzed by glutathione reductase. (C)</p> Signup and view all the answers

Which enzyme plays a crucial role in defending the body against hydrogen peroxide?

<p>Glutathione peroxidase (B)</p> Signup and view all the answers

What is the primary function of reduced glutathione (GSH) in the detoxification process?

<p>To detoxify hydrogen peroxide (B)</p> Signup and view all the answers

How does the cell regenerate GSH after it has reacted with hydrogen peroxide?

<p>Via a reaction catalyzed by glutathione reductase using NADPH (C)</p> Signup and view all the answers

Which process requires GSH for the protection of cell membranes from free radicals and peroxides within the cell?

<p>Oxidation to UDP-glucuronic acid (C)</p> Signup and view all the answers

What is the consequence of oxidation of sulfhydryl groups in proteins, including hemoglobin?

<p>Formation of denatured proteins (B)</p> Signup and view all the answers

Which factor is crucial for maintaining RBC deformability and preventing their removal by macrophages?

<p>RBC membrane rigidity (D)</p> Signup and view all the answers

In G6PD deficiency, which pathway provides the primary means of generating NADPH in RBCs?

<p>Pentose phosphate pathway (A)</p> Signup and view all the answers

What precipitating factor in G6PD deficiency leads to hemolytic anemia upon exposure?

<p>Antibiotics like sulfamethoxazole (C)</p> Signup and view all the answers

What is the role of Glucose 6-phosphate dehydrogenase (G6PD) in the Hexose monophosphate shunt pathway?

<p>It initiates the pathway and is the rate-limiting step. (A)</p> Signup and view all the answers

How does NADPH regulate G6PD activity in the Hexose monophosphate shunt pathway?

<p>Directly inhibits G6PD activity. (C)</p> Signup and view all the answers

What is the significance of the NADPH/NADP+ ratio in the Hexose monophosphate shunt pathway?

<p>It ensures production of only the required amount of NADPH. (B)</p> Signup and view all the answers

What role does Insulin play in the Hexose monophosphate shunt pathway?

<p>Upregulates G6PD gene expression. (D)</p> Signup and view all the answers

Which product of the Hexose monophosphate shunt pathway is essential for the synthesis of nucleotides?

<p>Ribose-5-P (D)</p> Signup and view all the answers

What is the role of NADPH oxidase in white blood cells in the context of the text?

<p>Reducing O2 to superoxide anion for killing bacterial cells (A)</p> Signup and view all the answers

Which enzyme catalyzes the synthesis of nitric oxide as described in the text?

<p>Nitric oxide synthase (C)</p> Signup and view all the answers

What happens to nitric oxide (NO) due to its reaction with O2 as described in the text?

<p>It converts into nitrates and nitrites (D)</p> Signup and view all the answers

Which molecule has a very short half-life in tissues due to its reactivity with oxygen?

<p>Nitric oxide (NO) (A)</p> Signup and view all the answers

What is the endogenous antioxidant enzyme responsible for removing superoxide anion after bacterial cell killing?

<p>Superoxide dismutase (B)</p> Signup and view all the answers

What substrates are required for the synthesis of nitric oxide according to the text?

<p>Arginine, O2, and NADPH (D)</p> Signup and view all the answers

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Study Notes

Uronic Acid Pathway

  • The main aim of the uronic acid pathway is to detoxify bilirubin released during hemoglobin breakdown.
  • Glucuronic acid is produced in the uronic acid pathway.
  • The end product of glucuronic acid metabolism in humans is the detoxification of bilirubin.

Glucuronic Acid and Detoxification

  • Glucuronic acid contributes to detoxification by conjugating with bilirubin, making it water-soluble and excretable.

Cytochrome P450 Mono-Oxygenase System

  • The Cytochrome P450 mono-oxygenase system is responsible for detoxifying xenobiotics and metabolizing certain drugs in the human body.
  • NADPH provides the reducing equivalents (hydrogen) required for the series of reactions in the Cytochrome P450 mono-oxygenase system.

G6PD Deficiency

  • Glucose-6-phosphate dehydrogenase (G6PD) deficiency is characterized by hemolytic anemia due to the inability to detoxify oxidizing agents.
  • Neonatal jaundice typically appears 1–4 days after birth in individuals with G6PD deficiency.
  • G6PD deficiency shares a resistance effect with Sickle cell trait and thalassemias, providing protection against malaria.

Hexose Monophosphate Shunt

  • The Hexose monophosphate shunt is a parallel pathway to glycolysis, converting glucose 6-phosphate to fructose 6-phosphate and glyceraldehyde 3-phosphate.
  • The primary product generated from the conversion of glucose 6-phosphate in the Hexose monophosphate shunt is NADPH.
  • NADPH is crucial for maintaining the integrity of the red blood cell membrane.
  • The main function of the Hexose monophosphate shunt in the context of red blood cells is to generate NADPH for detoxification.

Glutathione and Detoxification

  • Glutathione peroxidase plays a crucial role in defending the body against hydrogen peroxide.
  • NADPH reduces oxidized glutathione (GSSG) back to reduced glutathione (GSH) after it reacts with hydrogen peroxide.
  • GSH is essential for protecting cell membranes from free radicals and peroxides within the cell.
  • The oxidation of sulfhydryl groups in proteins, including hemoglobin, can lead to the formation of denatured proteins.

G6PD Deficiency and RBCs

  • In G6PD deficiency, the Pentose phosphate pathway provides the primary means of generating NADPH in RBCs.
  • Oxidative stress, such as that caused by certain medications, can precipitate hemolytic anemia in individuals with G6PD deficiency.
  • G6PD plays a crucial role in regulating the NADPH/NADP+ ratio in the Hexose monophosphate shunt pathway.

Insulin and Nitric Oxide

  • Insulin has no role in the Hexose monophosphate shunt pathway.
  • Nitric oxide synthase catalyzes the synthesis of nitric oxide.
  • Nitric oxide (NO) reacts with O2 to form nitrate and nitrite.
  • Nitric oxide has a very short half-life in tissues due to its reactivity with oxygen.
  • Superoxide dismutase is the endogenous antioxidant enzyme responsible for removing superoxide anion after bacterial cell killing.
  • The substrates required for the synthesis of nitric oxide are L-arginine, oxygen, and NADPH.

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