Pyruvate Carboxylase and Biotin Prosthetic Group Quiz
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Questions and Answers

What is the primary function of gluconeogenesis in animals?

  • To maintain adequate glucose levels in the blood (correct)
  • To store excess glucose as glycogen
  • To convert fatty acids into glucose
  • To break down glucose into energy

    • Which organs are responsible for gluconeogenesis in animals?

  • Pancreas and lungs
  • Brain and muscle
  • Heart and spleen
  • Liver and kidney (correct)

    • What is the biggest consumer of glucose in the body?

  • Brain (correct)
  • Kidney
  • Muscle
  • Red blood cells

    • During which periods is gluconeogenesis particularly important?

    <p>Periods of fasting or starvation</p> Signup and view all the answers

    Which organ can use ketone bodies as an alternative fuel source?

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

    What is the role of oxaloacetate in gluconeogenesis?

    <p>Serves as an intermediate to synthesize phosphoenolpyruvate</p> Signup and view all the answers

    Which compound is synthesized from fructose-1,6-bisphosphate during gluconeogenesis?

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

    What is the final product of gluconeogenesis?

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

    Why is the reciprocal regulation between glycolysis and gluconeogenesis emphasized?

    <p>To maintain appropriate glucose levels based on metabolic needs</p> Signup and view all the answers

    What is the fate of glycerol released from adipose tissue?

    <p>It is taken up by the liver</p> Signup and view all the answers

    Which molecule is glycerol converted to in the liver?

    <p>Dihydroxyacetone phosphate</p> Signup and view all the answers

    What is the role of pyruvate kinase in glycolysis?

    <p>Generates ATP as a product</p> Signup and view all the answers

    Why is the conversion of pyruvate to phosphoenolpyruvate considered a strongly exergonic reaction?

    <p>It releases energy</p> Signup and view all the answers

    Where does the process of converting pyruvate to phosphoenolpyruvate start?

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

    Which of the following statements about gluconeogenesis is correct?

    <p>It involves the breakdown of ATP</p> Signup and view all the answers

    What provides the energy necessary for driving the carboxylation of pyruvate to oxaloacetate?

    <p>ATP hydrolysis</p> Signup and view all the answers

    What is the prosthetic group required by pyruvate carboxylase for carrying CO2 in a reactive manner?

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

    Why is acetyl CoA referred to as an obligate allosteric activator of pyruvate carboxylase?

    <p>It is required for the carboxylation reaction to occur</p> Signup and view all the answers

    Why does oxaloacetate need to be converted to malate for transport out of the mitochondria?

    <p>There is no transporter for oxaloacetate</p> Signup and view all the answers

    Which enzyme converts oxaloacetate to malate in order to facilitate its transport out of the mitochondria?

    <p>Malate dehydrogenase</p> Signup and view all the answers

    What happens to malate once it reaches the cytosol?

    <p>It is converted back to oxaloacetate</p> Signup and view all the answers

    Why does pyruvate carboxylase require acetyl CoA in addition to biotin?

    <p>To ensure the carboxylation reaction takes place</p> Signup and view all the answers

    What happens if there is no bound acetyl CoA to pyruvate carboxylase?

    <p>Carboxylation does not occur</p> Signup and view all the answers

    Which vitamin is biotin derived from?

    <p>'Vitamin B7</p> Signup and view all the answers

    Why does oxaloacetate need to be transported out of the mitochondria into the cytosol?

    <p>To continue its involvement in metabolic pathways outside the mitochondria</p> Signup and view all the answers

    What was surprising about the two enzymes, PFK-2 and FBPase-2?

    <p>They were present in the same protein.</p> Signup and view all the answers

    What became evident upon determining the structure of the bifunctional enzyme?

    <p>It had two distinct domains: one for kinase activity and another for phosphatase domain.</p> Signup and view all the answers

    What triggers the phosphorylation of the single serine residue in the regulatory domain of the bifunctional enzyme?

    <p>A rise in glucagon levels due to low blood sugar.</p> Signup and view all the answers

    What effect does phosphorylation of the serine residue have on the bifunctional enzyme's activities?

    <p>Activates the phosphatase activity domain and inhibits the kinase domain activity.</p> Signup and view all the answers

    Why is the phosphorylation of the single serine residue important for the regulation of the bifunctional enzyme?

    <p>It allows fine-tuning of the enzyme's activities based on blood sugar levels.</p> Signup and view all the answers

    Which hormone is responsible for signaling phosphorylation of the serine residue in response to low blood sugar?

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

    What cell signaling cascade leads to the phosphorylation of the serine residue in the regulatory domain?

    <p>$cAMP$ signal cascade</p> Signup and view all the answers

    What is a central role of the pentose phosphate pathway (PPP)?

    <p>To generate ribose 5-phosphate for nucleotide synthesis</p> Signup and view all the answers

    Which molecule serves as the currency of reducing power for most reductive biosynthetic reactions?

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

    What does ribose 5-phosphate, generated by the PPP, provide the sugar component for?

    <p>Nucleotide synthesis</p> Signup and view all the answers

    In what tissues is the pentose phosphate pathway (PPP) particularly active?

    <p>Tissues where biomolecule synthesis is high</p> Signup and view all the answers

    Which key molecule does the PPP share with glycolysis, leading to coordinated regulation?

    <p>Glucose 6-phosphate</p> Signup and view all the answers

    What is the primary function of NADPH in the pentose phosphate pathway?

    <p>Serve as a reducing agent in biosynthetic reactions</p> Signup and view all the answers

    How does ribose 5-phosphate contribute to the production of DNA and RNA?

    <p>By providing the sugar component necessary for nucleotide synthesis</p> Signup and view all the answers

    Why is it important that the regulation of the pentose phosphate pathway (PPP) and glycolysis are coordinated?

    <p>To maintain balance in energy and reducing power needs</p> Signup and view all the answers

    Which molecule is considered the currency of reducing power for most reductive biosynthetic reactions?

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

    In the Pentose Phosphate Pathway, what is the primary function of the oxidative phase?

    <p>To oxidize glucose-6-P and produce NADPH</p> Signup and view all the answers

    What is the main outcome of the non-oxidative phase of the Pentose Phosphate Pathway?

    <p>Conversion of ribulose-5-P to ribose-5-P</p> Signup and view all the answers

    Why is it important for the Pentose Phosphate Pathway to divert excess ribose-5-P to glycolysis?

    <p>To ensure a balance between NADPH and ribose-5-P levels</p> Signup and view all the answers

    Which molecule serves as a significant product of the Pentose Phosphate Pathway?

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

    What is the main role of the Pentose Phosphate Pathway in relation to glycolysis?

    <p>Interconvert excess 5-carbon sugars to glycolysis intermediates</p> Signup and view all the answers

    Which phase of the Pentose Phosphate Pathway involves the conversion of ribulose-5-P to ribose-5-P?

    <p>Non-oxidative phase</p> Signup and view all the answers

    Why does the Pentose Phosphate Pathway need a mechanism to divert excess ribose-5-P to glycolysis?

    <p>Because NADPH demand is greater than ribose-5-P requirement</p> Signup and view all the answers

    Which process is facilitated by the interconversion of 3-, 4-, 5-, 6-, and 7-carbon sugars in the Pentose Phosphate Pathway?

    <p><strong>Glycolysis</strong></p> Signup and view all the answers

    What is the main purpose of the Pentose Phosphate Pathway (PPP) as discussed in the text?

    <p>To generate NADPH and ribose 5-phosphate</p> Signup and view all the answers

    What is the significance of the PPP in relation to glycolysis?

    <p>It shares key intermediates with glycolysis and is coordinately regulated</p> Signup and view all the answers

    Which molecule is primarily used as the reducing power currency in most reductive biosynthetic reactions?

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

    What is the sugar component provided by ribose 5-phosphate synthesized in the PPP for nucleotide production?

    <p>DNA and RNA</p> Signup and view all the answers

    Why is it crucial for the PPP to generate ribose 5-phosphate?

    <p>To act as a precursor for nucleotide synthesis</p> Signup and view all the answers

    What is the relationship between the PPP and NADPH production?

    <p>The PPP generates NADPH, acting as a source of reducing power</p> Signup and view all the answers

    How does the Pentose Phosphate Pathway (PPP) contribute to nucleotide synthesis?

    <p>By producing ribose 5-phosphate, a sugar component for nucleotides</p> Signup and view all the answers

    How does the regulation of the Pentose Phosphate Pathway (PPP) relate to glycolysis?

    <p>PPP and glycolysis share intermediates and are coordinately regulated.</p> Signup and view all the answers

    What is the rate-limiting step in the Pentose Phosphate Pathway (PPP)?

    <p>Catalysis of glucose-6-P dehydrogenase</p> Signup and view all the answers

    What is the primary role of NADP+ in the Pentose Phosphate Pathway?

    <p>To act as a substrate for glucose-6-P dehydrogenase</p> Signup and view all the answers

    Why does a high concentration of NADPH result in a low rate through the PPP?

    <p>The reaction catalyzed by glucose-6-P dehydrogenase is rate-limited by NADP+ availability</p> Signup and view all the answers

    What factor primarily determines which pathway glucose-6-P will be funneled into?

    <p>Cytosolic concentration of NADP+</p> Signup and view all the answers

    Why is glucose-6-P considered a key molecule in the regulation of the Pentose Phosphate Pathway?

    <p>It is a limiting factor for NADPH production</p> Signup and view all the answers

    What would be the consequence of a high concentration of NADPH in terms of PPP activity?

    <p>Decreased PPP activity due to inhibition by NADPH</p> Signup and view all the answers

    How does the cytosolic concentration of NADP+ impact the Pentose Phosphate Pathway?

    <p>It determines the rate of glucose-6-P conversion in PPP</p> Signup and view all the answers

    What is the primary function of the oxidative phase in the Pentose Phosphate Pathway?

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

    What is the second major product of the Pentose Phosphate Pathway?

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

    Why is it important for the PPP to interconvert sugars of different carbon lengths?

    <p>To provide a way to convert excess 5-carbon sugars to glycolysis intermediates</p> Signup and view all the answers

    What is the fate of excess ribose-5-P that needs to be diverted from the PPP?

    <p>Metabolized into useful components in glycolysis</p> Signup and view all the answers

    Which phase of the PPP involves converting ribulose-5-P to ribose-5-P?

    <p>Non-Oxidative Phase</p> Signup and view all the answers

    What is the purpose of producing NADPH in the Pentose Phosphate Pathway?

    <p>Provide reducing power for biosynthetic reactions</p> Signup and view all the answers

    Why does the PPP produce more NADPH than ribose-5-P?

    <p>NADPH is needed more than ribose-5-P in cellular processes</p> Signup and view all the answers

    What is the significance of interconverting 3-, 4-, 5-, 6-, and 7-carbon sugars in the PPP?

    <p>To facilitate conversion of excess 5-carbon sugars to glycolysis intermediates</p> Signup and view all the answers

    In Mode 3, where is the scenario with the need for greater NADPH than ribose-5-P, what is the fate of the ribulose-5-P produced by the oxidative portion of the PPP?

    <p>Converted to ribose-5-P</p> Signup and view all the answers

    In Mode 4, which statement best explains how glucose-6-P can produce ATP despite ATP not being directly produced by the PPP?

    <p>Fructose-6-P is produced by the PPP and then enters glycolysis.</p> Signup and view all the answers

    Which metabolite produced in Mode 4 can directly contribute to ATP production?

    <p>Glyceraldehyde-3-P</p> Signup and view all the answers

    What is the end result of every glucose-6-P being oxidized in Mode 3?

    <p>$6 CO_2$ with $12$ NADPH produced</p> Signup and view all the answers

    Which phase of the Pentose Phosphate Pathway produces NADPH and includes the conversion of glucose-6-P to ribulose-5-P?

    <p>Oxidative phase</p> Signup and view all the answers

    What is the primary purpose of converting ribulose-5-P to ribose-5-P in Mode 3?

    <p>To replenish NADPH</p> Signup and view all the answers

    Which metabolite from the PPP can be utilized for gluconeogenesis to produce glucose-6P in Mode 3?

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

    What is the significance of every glucose-6-P being oxidized to 6CO2 in Mode 3?

    <p>$CO_2$ reflects complete oxidation of glucose-$6P$</p> Signup and view all the answers

    Which metabolite conversion occurs first after glucose-6P is oxidized in Mode 4?

    <p>$Ribulose-$5P</p> Signup and view all the answers

    'Both NADPH and ATP are required' refers to Mode 4 in which glucose-$6P$ oxidation requires both molecules. Which pathway is essential for NADPH production in this mode?

    <p>$PPP$ (Pentose Phosphate Pathway)</p> Signup and view all the answers

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