Biochemistry of Saccharomyces cerevisiae
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Questions and Answers

What characterizes a cycling metabolic pathway?

  • Intermediates must be abundant for the pathway to function.
  • It operates with an amphilbolic nature, utilizing catalytic intermediates. (correct)
  • It has a linear progression with constant end product accumulation.
  • It aims to avoid any accumulation of end products.

    • How do allosteric activators affect enzyme activity?

  • They increase the Km and decrease Vmax.
  • They prevent substrate binding at the active site.
  • They decrease the Km and increase Vmax. (correct)
  • They promote irreversible inhibition of the enzyme.

    • What is an example of feedback inhibition in metabolic pathways?

  • The accumulation of intermediates to enhance enzymatic function.
  • Substrates acting as feed-forward activators.
  • Allosteric effectors binding at the active site.
  • End products inhibiting key enzymes in the pathway. (correct)

    • Which of the following statements about spiral metabolic pathways is correct?

    <p>They are structured to prevent accumulation of intermediates.</p> Signup and view all the answers

    What is the role of non-covalent allosteric effectors in enzyme activity modulation?

    <p>They affect the catalytic efficiency by binding at allosteric sites.</p> Signup and view all the answers

    What are the end products of glycolysis?

    <p>2 pyruvate, 2 ATP, and 2 NADH</p> Signup and view all the answers

    How is glycolysis regulated?

    <p>By the end product ATP and effectors on key enzymes</p> Signup and view all the answers

    What is the purpose of ATP in relation to glycolysis?

    <p>To support anabolic reactions and biomass production</p> Signup and view all the answers

    What are the main products of the pentose phosphate pathway?

    <p>NADPH and Ribose-5P</p> Signup and view all the answers

    What controls the pentose phosphate pathway?

    <p>The NADPH/NADP+ ratio and ATPMg</p> Signup and view all the answers

    What role does NADH play after glycolysis?

    <p>It is converted to NAD+ through fermentation or respiration</p> Signup and view all the answers

    What is controlling the glycolytic flux?

    <p>Various metabolic control mechanisms</p> Signup and view all the answers

    How are energy stores created during glycolysis?

    <p>By generating ATP and storing glucose as glycogen</p> Signup and view all the answers

    What is the standard free energy change of ATP hydrolysis?

    <p>-32.2 kJ/mol</p> Signup and view all the answers

    Which reaction represents substrate-level phosphorylation?

    <p>PEP + ADP → Pyruvate + ATP</p> Signup and view all the answers

    How is the electrochemical potential of H+ calculated?

    <p>μH+ = RT ln[H+] + zFY</p> Signup and view all the answers

    In a prokaryotic cell, where is the classical respiratory chain located?

    <p>Plasma membrane</p> Signup and view all the answers

    Which form of energy is associated with NAD(P)+ and NAD(P)H?

    <p>Redox energy</p> Signup and view all the answers

    The relationship between flux and rates in metabolic reactions can be described how?

    <p>Flux = rate B - rate A</p> Signup and view all the answers

    Which component has a higher energy state that contributes to ATP synthesis during chemiosmotic coupling?

    <p>H+ gradient</p> Signup and view all the answers

    What is the stoichiometry of NADH to ATP synthesis in the respiratory chain?

    <p>1 NADH produces 2.5 ATP</p> Signup and view all the answers

    What type of coupling is seen between H+ transport and ATP synthesis?

    <p>Electrochemical coupling</p> Signup and view all the answers

    What is the role of ATP in biological systems?

    <p>Serving as the primary energy currency</p> Signup and view all the answers

    What is meant by the term 'rate limiting step' in a metabolic pathway?

    <p>It is the step that determines the overall rate of the pathway.</p> Signup and view all the answers

    What does the concept of 'Metabolic Control Analysis' suggest?

    <p>Enzymes contribute to the flux to varying degrees.</p> Signup and view all the answers

    What is the correct expression for the control coefficient in relation to enzyme concentration and flux?

    <p>$C = \frac{dJ}{dE} \cdot \frac{E}{J}$</p> Signup and view all the answers

    How does an increase in ATP utilization rate affect the flux of glycolysis?

    <p>It can increase the flux of glycolysis.</p> Signup and view all the answers

    What is the main conclusion from the concept of metabolic control?

    <p>Concentration changes of any enzyme can affect the entire pathway's flux.</p> Signup and view all the answers

    What factor is NOT considered when analyzing the flux through a metabolic pathway?

    <p>Temperature of the environment.</p> Signup and view all the answers

    In the context of pathways, what does flux (J) primarily refer to?

    <p>The speed at which products are formed.</p> Signup and view all the answers

    Which of the following scenarios illustrates the concept of metabolic control best?

    <p>Increasing concentration of one enzyme leads to double the flux.</p> Signup and view all the answers

    What is the main product of glycolysis in yeast?

    <p>Fructose-6-P</p> Signup and view all the answers

    Which enzyme is directly involved in the conversion of glucose to G6P in the metabolic pathway?

    <p>Gfa1p</p> Signup and view all the answers

    In the biosynthesis of chitin, which molecule serves as a building block in the pathway?

    <p>UDP-N-acetylglucosamine</p> Signup and view all the answers

    According to the flux equation, how is the rate of chitin production calculated?

    <p>Chitin content multiplied by the growth rate</p> Signup and view all the answers

    Which compounds are involved in the regulation of chitin synthesis?

    <p>Glu and Gln</p> Signup and view all the answers

    Which enzyme is NOT part of the chitin biosynthesis pathway?

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

    What best characterizes the regulation of glycolysis in yeast?

    <p>Regulated mainly at the PFK step</p> Signup and view all the answers

    Which step in the metabolic pathway shows the highest correlation with chitin deposition?

    <p>The transcript levels of GFA1</p> Signup and view all the answers

    What role does Gfa1p play in chitin biosynthesis?

    <p>Facilitates the formation of UDP-N-acetylglucosamine</p> Signup and view all the answers

    How does transcription level affect chitin production?

    <p>Controls flux of chitin production</p> Signup and view all the answers

    What is the primary form of carbohydrate reserve present in yeasts?

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

    In the metabolic pathways discussed, what does UTP convert into?

    <p>UDP-N-acetylglucosamine</p> Signup and view all the answers

    Which aspect of cell metabolism does 'control' refer to in the context provided?

    <p>Optimization of production</p> Signup and view all the answers

    What does the relationship slope of 0.90 signify in the context of chitin production?

    <p>There is a strong correlation between Gfa1p activity and chitin production</p> Signup and view all the answers

    Study Notes

    Glycolysis

    • NADH is utilized in fermentation and aerobic respiration, regenerating NAD+ for glycolysis.
    • ATP is consumed for anabolic reactions and converted to ADP and Pi in substrate level phosphorylation.
    • End products of glycolysis include 2 pyruvate, 2 ATP, and 2 NADH.
    • Glycolysis is regulated by key enzyme effectors, primarily by ATP levels.
    • Glycolytic flux is controlled by Metabolic Control Analysis principles and homeostasis.

    Pentose Phosphate Pathway (PPP)

    • Major products of the PPP are NADPH and Ribose-5-P.
    • PPP regulation depends on the NADPH/NADP+ ratio and also on ATP concentration affecting glucose-6-phosphate dehydrogenase.

    Energy Forms in Cells

    • Three forms of energy: Chemical (ATP), Redox (NAD(P)+/NAD(P)H), and Chemiosmotic (proton gradient).
    • ATP is formed through substrate-level phosphorylation, yielding low ATP per glucose (e.g., 2 ATP in yeast fermentation).

    Respiratory Chain

    • Consists of four electron transport complexes in a membrane, essential for proton pumping.
    • Prokaryotic respiratory chains are located in the plasma membrane, while eukaryotes have them in the mitochondrial inner membrane.

    Metabolic Pathway Structures

    • Linear pathways yield end-product accumulation (e.g., amino acid synthesis).
    • Cycling pathways, like the Krebs cycle, maintain catalytic intermediates efficiently.
    • Spiral pathways prevent dilution of intermediates, ensuring production stability (e.g., fatty acid metabolism).

    Enzyme Activity Modulation

    • Enzyme activity control occurs through allosteric regulation—non-covalent effectors affect Km and Vmax of enzymes.
    • Feedback inhibition is common, such as ATP inhibiting PFK in glycolysis, while feed-forward activation involves substrate enhancement.

    Metabolic Control Analysis (MCA)

    • Defines control coefficients to quantify each enzyme's contribution to pathway flux.
    • The flux of metabolic pathways can be impacted by changes in enzyme concentration or activity levels.

    Chitin Biosynthesis in Yeast

    • Chitin production flux correlates with the concentration of enzymes involved in its biosynthesis, particularly Gfa1p, Gna1p, and Agm1p.
    • Control of chitin biosynthesis mainly occurs at the transcriptional level, indicating regulation strategies focus on gene expression dynamics.

    Summary of Regulatory Concepts

    • Regulation focuses on maintaining homeostasis within cells.
    • Control relates to productivity and efficiency of metabolic pathways, influencing cellular output and energy usage patterns.

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    Description

    This quiz explores the metabolic pathways of Saccharomyces cerevisiae, focusing on glycolysis and carbohydrate reserves. Test your knowledge on glucose utilization, glycolytic enzymes, and the roles of various metabolites in yeast. Perfect for students studying biochemistry or microbiology.

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