Glycogenesis Process Quiz
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Questions and Answers

What initiates the branching process in glycogenesis?

  • Glycogen synthase
  • Glucose-1-phosphate
  • A chain of 8 to 10 glycosidic residues (correct)
  • Glycogenin

    • What role does insulin play in glycogenesis?

  • Converts glucose directly into glycogen
  • Stimulates glycogenesis via dephosphorylation (correct)
  • Inhibits glycogen breakdown
  • Stimulates glycogenesis via phosphorylation

    • Which enzyme converts Glucose-1-phosphate to UDP-glucose?

  • Glycogen synthase
  • Glucokinase
  • UDP-glucose pyrophosphorylase (correct)
  • Phosphoglucomutase

    • How does glycogen synthase contribute to glycogen synthesis?

    <p>It binds to the growing chain and adds UDP-glucose</p> Signup and view all the answers

    What type of bond does the branching enzyme create in glycogen?

    <p>α(1→6) bonds</p> Signup and view all the answers

    What is the primary role of ATP in cellular metabolism?

    <p>To serve as a coupling molecule between exergonic and endergonic reactions</p> Signup and view all the answers

    What happens to the phosphoanhydride bonds in ATP during hydrolysis?

    <p>They release energy that can be used for cellular processes</p> Signup and view all the answers

    What initiates the digestion of carbohydrates in the mouth?

    <p>Salivary amylase</p> Signup and view all the answers

    Which statement about the composition of ATP is correct?

    <p>It consists of a nitrogenous base, a 5-carbon sugar, and three phosphoryl groups</p> Signup and view all the answers

    What is the initial product of starch digestion by salivary amylase?

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

    What role does lingual lipase play in digestion?

    <p>It begins the digestion of fats</p> Signup and view all the answers

    How does salivary amylase interact with starch?

    <p>By attacking α(1→4) glycosidic bonds of starch</p> Signup and view all the answers

    What is the primary function of enolase in glycolysis?

    <p>Remove a water group from 2-phosphoglycerate</p> Signup and view all the answers

    Which regulatory molecule has a positive effect on glycolysis?

    <p>Fru-2,6-BisP</p> Signup and view all the answers

    What is produced alongside pyruvic acid during the reaction catalyzed by pyruvate kinase?

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

    Which of the following statements about fermentation is correct?

    <p>Fermentation can occur anaerobically.</p> Signup and view all the answers

    Which enzyme is responsible for converting pyruvate to lactate in anaerobic conditions?

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

    What is the role of pyruvate decarboxylase in alcohol fermentation?

    <p>Remove CO2 from pyruvate</p> Signup and view all the answers

    Which of the following does NOT act as a negative regulator of glycolysis?

    <p>Fru-1,6-BisP</p> Signup and view all the answers

    During alcohol fermentation, which compound is reduced using NAD+?

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

    Where does gluconeogenesis primarily occur in the body?

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

    How many ATP molecules are generated during the process of glycolysis when two molecules of PEP are utilized?

    <p>2</p> Signup and view all the answers

    What function does lysozyme serve in digestion?

    <p>It provides an antiseptic function.</p> Signup and view all the answers

    Which enzyme specifically breaks α(1→6) bonds during carbohydrate digestion?

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

    Which of the following carbohydrates is converted to glucose and galactose?

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

    What role does α-amylase play in carbohydrate digestion?

    <p>It breaks α(1→4) bonds.</p> Signup and view all the answers

    How do D-Glucose, D-Galactose, and D-Fructose primarily enter the intestinal cells?

    <p>Via hexose transporter proteins.</p> Signup and view all the answers

    What is required for the symport that transports glucose into the cell of the small intestine to function?

    <p>Binding of sodium ions.</p> Signup and view all the answers

    Which enzyme converts maltose into two molecules of glucose?

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

    Which statement best describes an aspect of carbohydrate digestion?

    <p>Some carbohydrates require enzymes for hydrolysis.</p> Signup and view all the answers

    What is a consequence of insufficient enzymes in carbohydrate digestion?

    <p>Malabsorption of indigestible material.</p> Signup and view all the answers

    What is the primary function of fiber in the gastrointestinal tract?

    <p>Helps movement through the GIT</p> Signup and view all the answers

    Which condition is associated with flattening of the villi and results in malabsorption?

    <p>Coeliac disease</p> Signup and view all the answers

    What are the end products of glycolysis?

    <p>2 Pyruvates and 4 ATP</p> Signup and view all the answers

    Which enzyme catalyzes the conversion of D-glucose to glucose-6-phosphate in glycolysis?

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

    What role does anaerobic fermentation by intestinal flora play in digestion?

    <p>It produces gas such as hydrogen and carbon dioxide</p> Signup and view all the answers

    Which of the following issues can result from malabsorption?

    <p>Visible fat in feces</p> Signup and view all the answers

    What is the primary function of acetyl CoA in metabolism?

    <p>It carries 2-C fragments into the TCA cycle</p> Signup and view all the answers

    What occurs during the isomerization step of glycolysis?

    <p>G6P is rearranged into fructose 6-phosphate</p> Signup and view all the answers

    Which of the following best explains lactase deficiency's effect on digestion?

    <p>It results in the fermentation of lactose by gut bacteria, causing gas</p> Signup and view all the answers

    What is the consequence of having inadequate mucosal surface for absorption?

    <p>Malabsorption of nutrients</p> Signup and view all the answers

    Study Notes

    Carbohydrate Metabolism

    • Carbohydrates, proteins, and lipids are degraded to release energy
    • Carbohydrates are the most easily utilized energy source
    • Digestion starts in the mouth with salivary amylase, breaking down starch to maltose and dextrins
    • Salivary amylase is inactivated by stomach acid (pH 5.6-7)
    • Lingual lipase begins fat digestion, active in both alkaline and acidic pH
    • Digestion continues in the small intestine
    • Different enzymes break down various disaccharides (e.g., maltase breaks down maltose, sucrase breaks down sucrose, lactase breaks down lactose)
    • Monosaccharides (glucose, fructose, galactose) are absorbed passively or via hexose transporter (symport)
    • Glucose is actively transported into the intestinal cells, driven by the high extracellular Na+ concentration

    ATP - Cellular Energy Currency

    • Catabolism degrades carbohydrates, proteins, and lipids
    • Cells utilize an energy conversion strategy that oxidizes glucose
    • Energy release occurs at various points in the pathway
    • Energy is stored in adenosine triphosphate (ATP) bonds
    • A mole of glucose yields 686 kcal
    • ATP serves as a "go-between" molecule, coupling exergonic catabolic reactions with endergonic anabolic reactions
    • ATP captures energy as phosphoanhydride bonds
    • Hydrolysis of these bonds provides energy for cellular processes

    ATP - Molecule Structure

    • ATP is a nucleotide composed of:
      • Adenine (nitrogenous base)
      • Ribose (5-carbon sugar)
      • Three phosphoryl groups
    • A phosphoester bond connects the first phosphoryl group to ribose
    • Phosphoanhydride bonds link the second and third phosphoryl groups

    Phosphoanhydride Bond Hydrolysis

    • Hydrolysis of phosphoanhydride bonds releases large amounts of energy used for cellular processes

    Overview of Catabolic Processes

    • Carbohydrates, fats, and proteins are degraded to release energy
    • This process occurs in three stages:
      • Stage 1: Breakdown of large molecules into simpler units (e.g., proteins to amino acids, carbohydrates to monosaccharides, fats to fatty acids and glycerol)
      • Stage 2: Conversion of monomers into usable forms for the citric acid cycle
      • Stage 3: Complete oxidation and ATP production

    Saliva Composition and Function

    • Carbohydrate digestion begins in the mouth
    • Saliva consists of mucus, amylase, and lingual lipase:
      • Mucus (mucins and mucopolysaccharides): Lubricates food
      • Amylase: Initiates starch breakdown
      • Lingual lipase: Starts fat digestion
    • Saliva functions include tasting, moistening, facilitating swallowing, speech, preventing calcium phosphate deposition, protecting teeth against bacterial acids, and providing a beneficial antiseptic function.

    Salivary Amylase

    • Attacks alpha(1-4) glycosidic bonds of starch (amylose and amylopectin)
    • Breaks down starch into maltose and dextrins
    • Dextrins are short glucose polymers linked by alpha(1-4) or alpha(1-6) bonds

    Lingual Lipase

    • Similar to gastric lipase, involved in the initial phase of fat digestion
    • Active in both alkaline (mouth) and acidic (stomach) pH conditions
    • Converts triglycerides into monoacylglycerol, glycerol, and fatty acids

    Carbohydrate Digestion and Absorption

    • a-amylase breaks down starch; maltase, sucrase and lactase finish breaking down disaccharides
    • Glucose, fructose, and galactose are absorbed into the intestinal cells either via simple diffusion or assisted by the hexose transporter, which utilizes a symport with Na+.

    Carbohydrate Absorption

    • D-glucose, D-galactose, and D-fructose can diffuse passively through the intestinal villi
    • Luminal membranes of small intestine mucosal cells contain a symport to transport glucose into the cell, requiring Na+ binding to the transport protein.

    The Cori Cycle

    • The Cori cycle is an important metabolic pathway that connects lactate produced in muscle tissue during anaerobic conditions with glucose production in the liver.
    • The glucose produced by the liver is then returned to the muscle tissue to be used as fuel.

    Glycogenolysis

    • The process of glycogen degradation to glucose, controlled by glucagon and epinephrine
    • It involves two steps:
      • Step 1: Removal of terminal glucose as G-1P, utilizing glycogen phosphorylase
      • Step 2: Removal of the last glucose at the alpha(1-6) linkage by a debranching enzyme

    Glycogen Phosphorylase

    • Catalyzes the cleavage of alpha(1->4) glycosidic bonds in glycogen, releasing glucose-1-phosphate

    Debranching Enzyme

    • Transfers a trisaccharide unit to an exposed chain end using its transferase activity
    • Hydrolyzes the alpha (1->6) linkage to release the last glucose molecule at a branch point.

    Phosphoglucomutase

    • Converts glucose-1-phosphate (G-1-P) into glucose-6-phosphate (G-6-P)

    Glycogenesis

    • The process of glycogen synthesis from glucose precursors.
    • It occurs in two main stages:
      • Activation of glucose to form UDP-glucose
      • Glycogen synthesis by glycogen synthase and branching enzyme
    • Insulin stimulates glycogenesis in case of high blood sugar
    • Glucagon stimulates glycogen breakdown In cases of low blood sugar

    Glycogenesis: Glycogen Synthase

    • Adds UDP-glucose to the end of glycogen chains, resulting in an increase in a(1->4) bonds

    Glycogenesis: Branching Enzyme

    • Transfers oligosaccharide units from the non-reducing ends of glycogen chains to the interior of the glycogen, resulting in a-1-6-branching

    Aerobic Respiration & Energy Production

    • Breakdown of food in the presence of oxygen to produce ATP
    • Oxidative phosphorylation generates ATP from energy in oxidative reactions
    • Enzymes are located in the mitochondrial matrix, passing electrons from NAD+ or FAD to the electron transport system (ETC) and then to O₂
    • Protons are transferred to the intermembrane space, creating a proton gradient that drives ATP synthesis

    Mitochondria

    • "Shoe-shaped" organelles with a dual membrane structure, including an outer membrane with pores, allowing small molecule passage, and an inner membrane with highly folded cristae increasing surface area

    Conversion of Pyruvate to Acetyl CoA

    • Pyruvate produced from glycolysis enters the mitochondria
    • Pyruvate must be decarboxylated to acetyl CoA in order to enter the citric acid cycle
    • This oxidation also results in NAD+ being reduced to NADH

    Pyruvate Dehydrogenase Complex

    • A complex of three enzymes responsible for the conversion of pyruvate to acetyl CoA, involving reactions of decarboxylation, oxidation, and high-energy coenzyme attachment

    Role of Acetyl CoA in Metabolism

    • Produced from glucose, fatty acids, and amino acids
    • Acetyl CoA carries the acetyl group into the citric acid cycle for further oxidation
    • Production of ATP from acetyl CoA is via the citric acid cycle and ETC
    • Precursor for cholesterol and fatty acids, and the production of eicosanoids and phospholipids

    Citric Acid Cycle (TCA cycle)

    • The final stage in the breakdown of nutrients
    • Acetyl CoA and oxaloacetate enter the cycle, where the acetyl group is completely oxidized to 2 CO2
    • High-energy electrons are released and transferred to NAD+ and FAD to produce NADH and FADH2
    • A molecule of GTP (or ATP) is produced per cycle

    ETC & Oxidative Phosphorylation

    • Electron transport chain (ETC) in the inner mitochondrial membrane involves electron carriers
    • Enzyme ATP synthase makes ATP from the proton gradient
    • NADH produces 3 ATPs

    Hydrogen Ion Gradient

    • Protons (H+) are pumped into the intermembrane space via ETC carriers
    • The proton gradient drives ATP synthesis through ATP synthase

    Uncoupling Proteins (UCPs)

    • UCPs are inner mitochondrial membrane proteins
    • These proteins allow protons to leak back across the membrane generating heat instead of ATP

    Energy Outcome from One Glucose Molecule

    • In aerobic respiration, one molecule of glucose can generate 36 ATPs with varying amounts from glycolysis, TCA cycle, and ETC (NADH, FADH2)

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    Description

    Test your knowledge on the glycogenesis process through a series of questions that cover key aspects such as the role of insulin, enzyme activity, and bond formation in glycogen synthesis. Explore the different steps and mechanisms involved in this critical metabolic pathway.

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