BTE 202: Metabolism Lecture 8
24 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the role of Protein Phosphatase in the regulation of the PDH complex?

  • It inhibits PDH activity in the presence of ATP.
  • It phosphorylates PDH to activate it.
  • It activates the PDH complex in the presence of high NADH.
  • It reverses phosphorylation to restore PDH activity. (correct)

    • Which molecule is known to allosterically activate PDH phosphatase?

  • Calcium ions (Ca2+)
  • AMP (correct)
  • ATP
  • NADH

    • What is indicated when pyruvate is in high abundance in the context of PDH regulation?

  • ATP and NADH levels are sufficient.
  • The PDH complex is inactivated and phosphorylated.
  • There is a high need for producing more ATP. (correct)
  • Calcium ions are not needed.

    • In the inactive form of the pyruvate dehydrogenase complex, what modification is present?

    <p>Phosphorylation</p> Signup and view all the answers

    Which condition activates the PDH phosphatase to turn on the PDH complex?

    <p>High levels of calcium ions (Ca2+)</p> Signup and view all the answers

    What effect does high ATP concentration have on pyruvate dehydrogenase activity?

    <p>It promotes the phosphorylation of PDH, inactivating it.</p> Signup and view all the answers

    Which substance indicates that there is a low need for ATP production?

    <p>High ATP levels</p> Signup and view all the answers

    Which type of enzyme is involved in the activation of the PDH complex?

    <p>Phosphatase</p> Signup and view all the answers

    What is the primary product of pyruvate decarboxylation in cellular respiration?

    <p>Acetyl-CoA</p> Signup and view all the answers

    Which stage of cellular respiration follows the conversion of pyruvate to acetyl-CoA?

    <p>Citric acid cycle</p> Signup and view all the answers

    What is the role of the PDH complex in metabolism?

    <p>Catalyzes the conversion of pyruvate to acetyl-CoA</p> Signup and view all the answers

    Which of the following is NOT one of the three enzymes of the PDH complex?

    <p>Lipoate Synthase</p> Signup and view all the answers

    How many cofactors are involved in the production of acetyl-CoA from pyruvate?

    <p>Five</p> Signup and view all the answers

    What is the main reaction catalyzed by the pyruvate dehydrogenase complex?

    <p>Oxidative decarboxylation of pyruvate</p> Signup and view all the answers

    Which vitamin is a component of NAD?

    <p>Niacin</p> Signup and view all the answers

    Which coenzyme is specifically known for its role in the PDH complex?

    <p>Coenzyme A (CoA-SH)</p> Signup and view all the answers

    During cellular respiration, what is released as a byproduct when pyruvate is converted to acetyl-CoA?

    <p>CO2</p> Signup and view all the answers

    How do NADH and Acetyl-CoA affect the pyruvate dehydrogenase enzyme?

    <p>They serve as negative allosteric regulators</p> Signup and view all the answers

    What function do the reduced electron carriers NADH and FADH2 serve in cellular respiration?

    <p>Store energy for oxidative phosphorylation</p> Signup and view all the answers

    What role does pyruvate dehydrogenase kinase play in the regulation of the PDH complex?

    <p>It mediates phosphorylation which inactivates pyruvate dehydrogenase</p> Signup and view all the answers

    What happens to the intermediates of the PDH complex during the reaction?

    <p>They bind irreversibly to the enzyme</p> Signup and view all the answers

    Which of these is a positive allosteric effector of the PDH complex?

    <p>Fructose-1,6-bisphosphate</p> Signup and view all the answers

    What type of modification primarily regulates the pyruvate dehydrogenase?

    <p>Covalent modification through phosphorylation</p> Signup and view all the answers

    Which molecule would inhibit the activity of the pyruvate dehydrogenase complex?

    <p>Acetyl-CoA</p> Signup and view all the answers

    Study Notes

    Cellular Respiration Overview

    • Aerobic conditions lead to the further oxidation of pyruvate into CO2 and H2O, a process called respiration.
    • Cellular respiration consists of three main stages:
      • Oxidation of organic fuel molecules (glucose, fatty acids, amino acids) to form acetyl-CoA.
      • Entry of acetyl groups into the citric acid cycle, which oxidizes them to CO2.
      • Energy conservation through the electron transport chain, generating ATP from reduced electron carriers NADH and FADH2.

    Production of Acetyl-CoA

    • Pyruvate is generated from glycolysis and undergoes decarboxylation to become acetyl-CoA and CO2.
    • This conversion is facilitated by the pyruvate dehydrogenase (PDH) complex, found in mitochondria of eukaryotes and cytosol of prokaryotes.

    Pyruvate Dehydrogenase (PDH) Complex

    • Comprises three enzymes:
      • Pyruvate Dehydrogenase (E1)
      • Dihydrolipoyl Transacetylase (E2)
      • Dihydrolipoyl Dehydrogenase (E3)
    • Contains five cofactors, four of which are derived from vitamins:
      • Thiamine pyrophosphate (TPP) from Vitamin B1
      • Lipoate
      • Coenzyme A (CoA-SH) from Vitamin B5
      • Flavin adenine dinucleotide (FAD) from Vitamin B2
      • Nicotinamide adenine dinucleotide (NAD) from Vitamin B3

    Regulatory Proteins in PDH Complex

    • The PDH complex includes regulatory proteins:
      • Pyruvate Dehydrogenase Kinase (PDK)
      • Phosphoprotein Phosphatase
    • These proteins regulate the activity of the PDH complex.

    Reaction Mechanism

    • PDH catalyzes an irreversible oxidative decarboxylation of pyruvate where the carboxyl group is released as CO2, forming acetyl-CoA.
    • Intermediates generated during this reaction remain bound to the enzyme complex and do not detach.

    Regulation of PDH Complex

    • Regulated by:
      • Allosteric Effectors:
        • Fructose-1,6-bisphosphate acts as a positive allosteric effector for E1.
        • NADH and acetyl-CoA serve as negative regulators through feedback inhibition.
      • Covalent Modification:
        • PDK, stimulated by NADH and acetyl-CoA, phosphorylates PDH, inhibiting its activity.
        • Protein phosphatase reverses this phosphorylation, reactivating PDH, influenced by AMP, NAD+, pyruvate, and Ca2+.

    Summary of Regulation

    • High levels of ATP or NADH lead to PDH phosphorylation and inactivation, indicating no need for ATP production.
    • Conversely, low ATP levels or high demands (indicated by high pyruvate, AMP, or calcium) stimulate PDH activity through dephosphorylation, promoting ATP synthesis.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    This quiz focuses on Lecture 8 of BTE 202, covering the conversion of pyruvate to Acetyl-CoA in cellular respiration. It highlights the aerobic process of metabolism and the stages involved in the oxidation of organic fuel molecules. Test your understanding of these essential biochemical processes.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser