Pentose Phosphate Pathway Overview
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Questions and Answers

Which component is primarily produced during the oxidative phase of the Pentose Phosphate Pathway?

  • Glucose 6-phosphate
  • Ribulose 5-phosphate
  • Erythrose 4-phosphate
  • NADPH (correct)

What is the primary function of ribose 5-phosphate produced in the Pentose Phosphate Pathway?

  • Synthesis of nucleotides (correct)
  • Synthesis of fatty acids
  • Synthesis of amino acids
  • Energy production

Which enzymes are involved in converting ribulose 5-phosphate back to glucose 6-phosphate during the non-oxidative phase?

  • Hexokinase and Lactonase
  • 6-Phosphogluconate dehydrogenase and Lactonase
  • Transketolase and Transaldolase (correct)
  • Glucose-6-phosphate dehydrogenase and Lactonase

In which cellular location does the Pentose Phosphate Pathway primarily take place?

<p>Cytosol (C)</p> Signup and view all the answers

What is the significance of NADPH produced in the Pentose Phosphate Pathway?

<p>It acts as an electron carrier in biosynthesis. (B)</p> Signup and view all the answers

What is the role of lactonase in the oxidative phase of the Pentose Phosphate Pathway?

<p>Hydrolysis of 6-phosphoglucono-lactone (C)</p> Signup and view all the answers

Which of the following is NOT a site where the Pentose Phosphate Pathway occurs?

<p>Skeletal muscle (D)</p> Signup and view all the answers

What is the primary type of reaction that occurs in the non-oxidative phase of the Pentose Phosphate Pathway?

<p>Reversible enzyme reactions (C)</p> Signup and view all the answers

Flashcards

Pentose Phosphate Pathway (PPP)

A metabolic pathway that produces NADPH, ribose 5-phosphate, and erythrose 4-phosphate, parallel to glycolysis.

NADPH in PPP

Reducing equivalent used in reductive biosynthesis reactions, like fatty acid synthesis.

Ribose 5-phosphate (R5P)

A 5-carbon sugar used for nucleotide and nucleic acid synthesis.

Oxidative Phase of PPP

The first phase of PPP, where NADPH is generated and glucose 6-phosphate is converted to ribulose 5-phosphate. It's not reversible.

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Glucose 6-phosphate dehydrogenase (G6PD)

Enzyme that catalyzes the first step in the oxidative phase of PPP.

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6-Phosphogluconate dehydrogenase

Enzyme responsible for converting 6-phosphogluconate to ribulose 5-phosphate, also generating NADPH.

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Non-oxidative Phase

The second phase, where ribulose 5-phosphate is converted back to glucose 6-phosphate through reversible reactions.

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Location of PPP

Metabolic pathway takes place in the cytosol of various cells, including liver and adipose tissues.

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Study Notes

Pentose Phosphate Pathway (PPP)

  • Glucose is broken down via glycolysis into pyruvate, then pyruvate is oxidized via the citric acid cycle to produce ATP in animal tissue.
  • The Pentose Phosphate Pathway (PPP), also known as the Hexose Monophosphate Pathway (HMP shunt) or Phosphogluconate pathway, is an alternative metabolic pathway.
  • The PPP produces ribose sugar, ATP, and two NADPH.
  • Unlike glycolysis, the PPP does not generate ATP.
  • The PPP occurs in the cytosol of cells in the liver, adipose tissue, lactating mammary gland, and cortex of the adrenal gland.
  • Glucose 6-phosphate + 2NADP+ + H₂O → ribose 5-phosphate + CO₂ + 2NADPH + 2H⁺

Function of Pathway

  • Generates NADPH for reductive biosynthesis (e.g., fatty acid synthesis).
  • Produces ribose 5-phosphate (R5P) for nucleotide and nucleic acid synthesis.
  • Produces erythrose 4-phosphate (E4P) for aromatic amino acid synthesis.

Phases of PPP

  • Oxidative (non-reversible) phase: Glucose 6-phosphate undergoes dehydrogenation and decarboxylation to yield a pentose (ribulose 5-phosphate).
  • Non-oxidative (reversible) phase: Ribulose 5-phosphate is converted back to glucose 6-phosphate via a series of reactions involving transketolase and transaldolase.
  • These two phases are distinct, with the first generating NADPH and the second synthesizing 5-carbon sugars.

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Description

This quiz explores the Pentose Phosphate Pathway (PPP), detailing its significance in metabolism, phases, and products. Understand how the PPP differs from glycolysis and its role in producing crucial metabolic intermediates like NADPH and ribose sugar.

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