Biology Chapter 5 Quiz
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Questions and Answers

What is generated during the citric acid cycle in mitochondria?

  • Glucose
  • NADH and FADH2 (correct)
  • Carbon dioxide
  • ATP only
  • Where does the digestion of carbohydrates first begin?

  • Small Intestine
  • Duodenum
  • Stomach
  • Mouth (correct)
  • What type of enzyme is salivary amylase?

  • Protease
  • Carbohydrate-splitting (correct)
  • Lipid-splitting
  • Nucleic acid-splitting
  • Which part of the digestive system has no carbohydrate-splitting enzyme at work?

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

    What is the role of GluT 2?

    <p>Glucose sensor in beta cells of pancreas</p> Signup and view all the answers

    Which enzyme hydrolyzes terminal α-1→4 glycosidic linkages in the Small Intestine?

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

    What is one of the key products of carbohydrate hydrolysis by lactase?

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

    Which transporter has a high affinity for glucose and is found in neurons and the brain?

    <p>GluT 3</p> Signup and view all the answers

    Which glucose transporter is primarily responsible for insulin-mediated glucose uptake?

    <p>GluT 4</p> Signup and view all the answers

    What is the primary mechanism through which glucose and galactose are absorbed in the intestine?

    <p>Active transport</p> Signup and view all the answers

    Which monosaccharide has the highest absorption rate in the intestine?

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

    Which glucose transporter is found in the liver endoplasmic reticulum?

    <p>GluT 7</p> Signup and view all the answers

    What role does sodium play in the absorption of glucose?

    <p>It is co-transported with glucose into intestinal cells.</p> Signup and view all the answers

    Which glucose transporter is not under the control of insulin?

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

    How does glucose exit intestinal cells into the bloodstream?

    <p>Through facilitated diffusion via GluT 2</p> Signup and view all the answers

    What impact does reduced GluT4 have on type 2 diabetes mellitus (DM)?

    <p>It reduces glucose uptake in muscle and fat cells.</p> Signup and view all the answers

    What is the net yield of ATP produced from one molecule of glucose during glycolysis?

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

    Which of the following enzymes is involved in the conversion of glucose to glucose 6-phosphate?

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

    During glycolysis, which compound is produced along with NADH?

    <p>1,3-Bisphosphoglycerate</p> Signup and view all the answers

    What factors increase the rate of glycolysis?

    <p>Increase in insulin concentration</p> Signup and view all the answers

    In the absence of oxygen, how many ATP molecules are produced from glycolysis?

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

    Which of the following statement about glycolysis is incorrect?

    <p>Glycolysis can only occur in the presence of oxygen.</p> Signup and view all the answers

    Which of the following mechanisms is involved in the regulation of glycolysis?

    <p>Changes in the rate of enzyme synthesis</p> Signup and view all the answers

    What is the primary role of phosphofructokinase in glycolysis?

    <p>To limit the rate of glycolysis</p> Signup and view all the answers

    What is the final product of glycolysis?

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

    Which of the following statements about pyruvate kinase is true?

    <p>It functions as an allosteric tetramer</p> Signup and view all the answers

    What inhibits the activity of phosphofructokinase?

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

    What effect does insulin have on glycolysis?

    <p>It increases the concentration of key glycolytic enzymes</p> Signup and view all the answers

    Which of the following enzymes is specifically inhibited by its product, glucose 6-phosphate?

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

    How do red blood cells primarily generate energy?

    <p>By glycolysis alone</p> Signup and view all the answers

    What is the major function of fructose 2,6-bisphosphate in metabolic regulation?

    <p>It acts as an inhibitor to gluconeogenesis</p> Signup and view all the answers

    What unique structural characteristic do mature erythrocytes possess?

    <p>They lack a nucleus and cytoplasmic structures</p> Signup and view all the answers

    What is the outcome of glucose oxidation regardless of oxygen availability?

    <p>Formation of pyruvic acid and lactic acid</p> Signup and view all the answers

    What is the biochemical significance of the Rapoport-Luebering shunt in red blood cells?

    <p>It allows for the production of 2,3-BPG which alters hemoglobin's affinity for oxygen.</p> Signup and view all the answers

    How does the ATP/ADP ratio behave in mature red blood cells?

    <p>It remains stable due to inactive ATPase activity.</p> Signup and view all the answers

    What effect does hexokinase deficiency have on BPG concentration in red blood cells?

    <p>BPG concentration decreases to about 2/3 of normal.</p> Signup and view all the answers

    What is true regarding the effect of 2,3-BPG on adult hemoglobin (Hb-A1)?

    <p>High 2,3-BPG concentration reduces oxygen affinity.</p> Signup and view all the answers

    What happens to the oxygen affinity of hemoglobin in pyruvate kinase deficiency?

    <p>It decreases, leading to less efficient oxygen unloading.</p> Signup and view all the answers

    How does competitive inhibition affect glycolysis in mature red blood cells?

    <p>It causes a cessation of glycolysis due to BPG accumulation.</p> Signup and view all the answers

    Which of the following statements accurately describes 2,3-BPG's role in fetal hemoglobin (Hb-F)?

    <p>Low 2,3-BPG concentration increases oxygen affinity.</p> Signup and view all the answers

    Study Notes

    Metabolism of Carbohydrates

    • The citric acid cycle (CAC) generates reducing equivalents, NADH and FADH2, as part of tertiary metabolism within mitochondria.
    • These reducing equivalents enter the electron transport chain (ETC) to release energy, contributing to cellular respiration.

    Digestion of Carbohydrates

    • Carbohydrates in the diet primarily consist of polysaccharides (starch, glycogen) and some disaccharides (sucrose, lactose).
    • They are hydrolyzed into monosaccharides (glucose, galactose, fructose) in the gastrointestinal tract (GIT).

    Digestion Process

    • Mouth: Saliva contains salivary amylase which begins carbohydrate digestion by hydrolyzing α-1→4 glycosidic bonds.
    • Stomach: No significant carbohydrate digestion occurs due to the absence of carbohydrate-splitting enzymes.
    • Duodenum: Mixing with pancreatic juice introduces pancreatic amylase, which continues the hydrolysis of polysaccharides.
    • Small Intestine: Intestinal juice contains multiple enzymes (amylase, lactase, maltase) that hydrolyze disaccharides and oligosaccharides to glucose.

    Transporters for Glucose

    • GluT 1: Found in RBCs, brain, and other tissues; responsible for glucose uptake.
    • GluT 2: Located in intestinal cells, liver, and pancreatic beta cells; acts as a glucose sensor with low affinity.
    • GluT 3: Present in neurons, with high affinity for glucose.
    • GluT 4: Found in skeletal muscle and adipose tissue; insulin-mediated uptake.
    • GluT 5: Serves as a fructose transporter in the small intestine.
    • GluT 7: Located in liver endoplasmic reticulum, involved in glucose transport.

    Absorption of Carbohydrates

    • Only monosaccharides are absorbed by the intestine, with varying absorption rates.
    • Simple/Passive Diffusion: Monosaccharides absorbed based on concentration gradients.
    • Facilitated Diffusion: Glucose and galactose absorption is active and energy-dependent, mediated by specific carrier molecules.

    Mechanism of Glucose Absorption

    • Co-transport: Glucose co-transported with sodium into intestinal cells via sodium-dependent glucose transporter-1 (S GluT-1).
    • Uniport: Glucose is transported into the bloodstream by GluT 2 without sodium dependency.
    • GluT4: Insulin-regulated glucose transporter in muscle and fat cells; impairment leads to insulin resistance.

    Glycolysis Overview

    • Converts one glucose molecule into two pyruvate molecules, producing two NADH and two ATP molecules.
    • Key pathway for energy generation and metabolic intermediates.

    Energy Yield

    • Aerobic Glycolysis: Produces a higher ATP yield in the presence of oxygen.
    • Anaerobic Glycolysis: Limited ATP yield (2 ATP) when oxygen is absent.

    Regulation of Glycolysis

    • Three primary regulatory mechanisms: enzyme synthesis changes, covalent modification, and allosteric regulation.
    • Hormonal influences: insulin boosts glycolysis by upregulating enzymes, while glucagon and catecholamines inhibit it.

    Key Enzymes in Glycolysis

    • Hexokinase: Phosphorylates glucose; inhibited by glucose-6-phosphate.
    • Phosphofructokinase: Rate-limiting step; allosterically regulated by ATP and fructose 2,6-bisphosphate.
    • Pyruvate Kinase: Converts phosphoenolpyruvate to pyruvate; regulated by fructose 1,6-bisphosphate and energy charge.

    Fermentation Pathways

    • Lactic acid and alcohol fermentation pathways follow glycolysis based on oxygen availability.

    Unique Features of Glycolysis in Red Blood Cells

    • Mature red blood cells rely exclusively on glycolysis for energy, lacking organelles that would utilize other metabolic pathways.
    • Pyruvate is continuously converted to lactic acid without the use of mitochondrial processes.

    Rapoport-Luebering Cycle

    • Glycolytic diversion produces 2,3-bisphosphoglycerate (2,3-BPG) in red blood cells, influencing hemoglobin’s oxygen affinity.

    Inherited Enzyme Deficiencies

    • Deficiencies in hexokinase and pyruvate kinase impact 2,3-BPG levels, affecting hemoglobin's oxygen binding.

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    Description

    Test your knowledge on key concepts in Chapter 5 of biology, focusing on the digestive system and metabolic pathways. This quiz covers the citric acid cycle, carbohydrate digestion, and the role of various enzymes such as salivary amylase. Perfect for students looking to reinforce their understanding of these essential processes.

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