Glycogen Formation and Breakdown
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Questions and Answers

Why can the liver provide glucose to other organs?

  • Because it contains more glycogen than muscle
  • Because it converts G6P into G1P
  • Because it produces glucose through gluconeogenesis
  • Because it can release glucose out of the cell (correct)

    • What is the reason that glucose is trapped in muscle cells?

  • Muscle cells do not convert glucose into G1P
  • Muscle cells can only phosphorylate glucose to G6P (correct)
  • Muscle cells use glucose solely for energy production
  • Muscle cells lack the enzymes to secrete glucose

    • What is the product formed from the phosphorylation of glucose?

  • Glucose-6-phosphate (G6P) (correct)
  • Limit dextrin
  • Glucose-1-phosphate (G1P)
  • Glycogen

    • What limits further cleavage of glycogen when it becomes limit dextrin?

    <p>The inability of glycogen phosphorylase to recognize residues</p> Signup and view all the answers

    Which coenzyme is involved in the conversion of vitamin B6 during this process?

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

    What is the primary function of oxidative deamination in amino acid metabolism?

    <p>To convert an amino acid to a keto acid while releasing ammonium ion</p> Signup and view all the answers

    Which coenzyme is involved in the action of glutamate dehydrogenase during oxidative deamination?

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

    What role does fumarate play in the context of the Krebs cycle after amino acid breakdown?

    <p>It reenters the Krebs cycle.</p> Signup and view all the answers

    Where does oxidative deamination primarily occur in the body?

    <p>In the mitochondria of the liver</p> Signup and view all the answers

    Which of the following amino acids can return to the TCA cycle through oxaloacetate?

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

    What kind of amino acids can be converted back to succinyl CoA?

    <p>Isoleucine, methionine, and valine</p> Signup and view all the answers

    How does glutamate dehydrogenase differ from other enzymes?

    <p>It can utilize multiple types of coenzymes.</p> Signup and view all the answers

    What is formed when ammonium ion combines with water molecules during oxidative deamination?

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

    What role does the niacin group play in metabolism?

    <p>It can become a coenzyme.</p> Signup and view all the answers

    What is the lifespan of red blood cells (RBC)?

    <p>80 to 120 days</p> Signup and view all the answers

    What happens to damaged red blood cells?

    <p>They are consumed by macrophages.</p> Signup and view all the answers

    What component of hemoglobin is processed into bilirubin?

    <p>Heme part</p> Signup and view all the answers

    Where does bilirubin go for conjugation and processing?

    <p>To the liver</p> Signup and view all the answers

    What is released from hemoglobin during its catabolism?

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

    What process utilizes alpha-ketoglutarate aside from the Krebs cycle?

    <p>Transamination processes</p> Signup and view all the answers

    What happens to alpha-ketoglutarate after its generation?

    <p>It is reused in metabolic pathways.</p> Signup and view all the answers

    What is the storage form of iron in the body?

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

    What substance is produced from the breakdown of the heme group?

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

    Which enzyme is responsible for converting bilirubin to its conjugated form?

    <p>UDP glucuronyl transferase</p> Signup and view all the answers

    What do stercobilin and urobilinogen turn into in the body?

    <p>Feces and urine</p> Signup and view all the answers

    Which of the following is a product produced from the gastrointestinal processing of conjugated bilirubin?

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

    Which organ primarily processes the unconjugated bilirubin created from the heme group?

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

    What process converts damaged red blood cells into bilirubin?

    <p>Heme degradation</p> Signup and view all the answers

    What is the main role of probiotics in the gastrointestinal system concerning bilirubin?

    <p>Process conjugated bilirubin</p> Signup and view all the answers

    What is the role of the gallbladder during fasting?

    <p>It releases stored bile to aid in lipid digestion.</p> Signup and view all the answers

    What happens to the TCA cycle during a state of fasting?

    <p>It slows down due to lack of glucose provision.</p> Signup and view all the answers

    Which of the following is a byproduct formed from beta-oxidation during fasting?

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

    Where do ketone bodies primarily form in the body?

    <p>Liver mitochondria</p> Signup and view all the answers

    What is the first ketone body produced during ketogenesis?

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

    Which of the following statements is true regarding lacteals?

    <p>They absorb lipids first in the small intestine.</p> Signup and view all the answers

    What catalyzes the production of β-Hydroxybutyrate from acetoacetate?

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

    How are lipids transported through the bloodstream after absorption?

    <p>As chylomicrons and other lipoproteins.</p> Signup and view all the answers

    What is formed through the condensation of two acetyl CoA molecules?

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

    Which substance will not result in ketone body formation?

    <p>Sufficient glucose levels</p> Signup and view all the answers

    What is the primary energy source produced during fasting?

    <p>Ketone bodies</p> Signup and view all the answers

    What triggers the production of ketone bodies in the liver?

    <p>Build-up of acetyl CoA</p> Signup and view all the answers

    What occurs to excess Acetyl CoA that is not used in the TCA cycle?

    <p>Converted to ketone bodies.</p> Signup and view all the answers

    What does lipolysis lead to during the fasting state?

    <p>Release of fatty acids and glycerol.</p> Signup and view all the answers

    What is the primary role of specific transporters in amino acid metabolism?

    <p>To transport individual amino acids into cells</p> Signup and view all the answers

    Which of the following accurately describes the digestion of proteins?

    <p>Involves hydrochloric acid and pepsin in the stomach</p> Signup and view all the answers

    What happens to excess amino acids that are not used by the body?

    <p>They are catabolized for energy</p> Signup and view all the answers

    Which process does NOT occur during protein catabolism?

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

    What is the primary function of hydrochloric acid in protein digestion?

    <p>To hydrolyze peptide bonds</p> Signup and view all the answers

    Which statement about amino acids is accurate?

    <p>They cannot be stored and must be catabolized for energy</p> Signup and view all the answers

    What triggers the release of zymogens in the small intestine?

    <p>The arrival of large polypeptides</p> Signup and view all the answers

    What is a key purpose of the urea cycle?

    <p>To excrete excess nitrogen from amino acid breakdown</p> Signup and view all the answers

    Which enzyme is primarily responsible for hydrolyzing peptide bonds during digestion?

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

    During amino acid catabolism, which group is removed first?

    <p>Amino group</p> Signup and view all the answers

    What is the approximate pH of hydrochloric acid in the stomach?

    <p>Acidic (1.5 - 2.0)</p> Signup and view all the answers

    In what part of the body does the catabolism of amino acids primarily occur?

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

    After amino acid catabolism, what is the fate of the carbon skeleton?

    <p>Used for energy production</p> Signup and view all the answers

    Study Notes

    Glycogen Formation and Breakdown

    • Glycogen is the storage form of carbohydrates in animals
    • Primarily found in muscle and liver tissues
    • Made up of alpha-d glucose units

    Glycogen Synthesis (Glycogenesis)

    • Insulin stimulates glycogen synthase and glucokinase
    • Main enzyme during fed state, enabling glucose entry into cells for storage or glycolysis
    • Glucagon and epinephrine inhibit glycogen synthase, preventing glycogen storage during fasting/starving
    • Crucial for storing excess glucose

    Glycogen Breakdown (Glycogenolysis)

    • Glycogenolysis is the opposite of glycogenesis
    • Important for releasing glucose during fasting/starving
    • Process influenced by hormones to release stored glucose
    • Insulin inhibits while glucagon and epinephrine stimulate glycogenolysis

    Glycogen Isomerization

    • Enzyme: Phosphoglucomutase
    • Converts glucose-1-phosphate to glucose-6-phosphate

    Glycogen Activation

    • UDP-glucose pyrophosphorylase catalyzes addition of UTP to glucose-1-phosphate, creating UDP-glucose
    • Important for glucose attachment to the glycogen chain

    Glycogen Branching

    • Enzyme: Amylo (α1→4) → α(1→6) transglucosidase
    • Forms α(1→6) bonds, creating branching points on the glycogen chain

    Glycogen Transfer

    • Enzyme: Glucan transferase
    • Transfers 3-8 glucosyl residues from the outer chain to the core chain to create branches

    Glycogen Debranching

    • Enzyme: Amylo α(1→6) glucosidase
    • Cleaves α(1→6) bonds, releasing free glucose

    Glycogenolysis - Summary

    • Cleavage of α(1→4) bonds → yields glucose-1-phosphate
    • Continue until the limit dextrin (4 glucosyl units)
    • Glucose-1-phosphate is converted to glucose-6-phosphate
    • Glucose-6-phosphatase (only in liver) converts glucose-6-phosphate to free glucose for release into bloodstream; muscle only produces glucose-6-phosphate

    Glycogenolysis - Liver vs. Muscle

    • Liver glycogenolysis produces free glucose for release into the blood
    • Muscle glycogenolysis produces glucose-6-phosphate which remains in the muscle, only to be later used during glycolysis

    Other Metabolic Pathways

    • Muscle glycogen → G6P → glycolysis; liver glycogen → G6P → glucose
    • Glucose-6-phosphate → free glucose (liver only)
    • Glucagon and epinephrine stimulate glycogen phosphorylase; insulin inhibits

    Other Important Notes

    • Mutase: shifts phosphate groups
    • Coenzyme: Vitamin B6 (Pyridoxal phosphate)
    • G6P in muscle can't be released to the bloodstream as glycogen is stored only for the muscle
    • G6P in liver converts glucose-6-phosphate to glucose for release in the blood stream

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    CHEM 301 Biochemistry Lecture Notes, 2024-2025 PDF

    Description

    This quiz explores the biochemical processes of glycogen synthesis and breakdown. It will cover key enzymes, hormonal regulation, and the significance of glycogen in energy storage and release. Test your understanding of glycogenesis and glycogenolysis with this engaging quiz!

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