Carbohydrate Metabolism Overview
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Questions and Answers

What is the primary role of carbohydrate metabolism in the body?

  • To exclusively store glucose as fat
  • To generate energy for various metabolic pathways (correct)
  • To convert fats directly into proteins
  • To synthesize hormones for muscle growth

    • What happens when carbohydrate metabolism is deranged?

  • It leads to collapse of the whole metabolic system (correct)
  • Only minor symptoms are observed
  • It enhances muscle performance
  • It primarily affects cardiovascular health

    • Which metabolic process is initiated by the digestion of carbohydrates?

  • Nucleotide digestion
  • Conversion to monosaccharides (correct)
  • Lipid metabolism
  • Protein synthesis

    • How does the liver contribute to carbohydrate metabolism?

    <p>It stores and distributes glucose in the body</p> Signup and view all the answers

    What is primarily formed during the breakdown of carbohydrates?

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

    Which statement is true about insulin's role in carbohydrate metabolism?

    <p>Insulin facilitates glucose uptake into cells</p> Signup and view all the answers

    Which process begins the complete oxidation of glucose?

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

    What is the fate of glucose in the body post-digestion?

    <p>It can be catabolized to produce ATP</p> Signup and view all the answers

    What happens if anaerobic metabolism is not maintained within the body?

    <p>The entire metabolic system may collapse</p> Signup and view all the answers

    What happens to glucose after it is converted to fatty acids?

    <p>It is stored in adipose tissue as triglycerides.</p> Signup and view all the answers

    How does glucose affect insulin secretion in β cells?

    <p>It stimulates electrical activity.</p> Signup and view all the answers

    Which aspect of carbohydrate metabolism is crucial for athletic performance?

    <p>Proper utilization of carbohydrates for energy production</p> Signup and view all the answers

    What kind of insulin precursor is synthesized in the β cells?

    <p>Pre-proinsulin</p> Signup and view all the answers

    What is the fate of glucose after its initial breakdown?

    <p>It is oxidized to synthesize ATP.</p> Signup and view all the answers

    What enzyme plays a key role in the processing of pro-insulin?

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

    What mechanism is responsible for the actual release of insulin from β cells?

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

    What is the role of insulin in regulating glucose transport in muscle and fat cells?

    <p>Insulin stimulates the transport of glucose across the cell membranes.</p> Signup and view all the answers

    Which glucose transporter is primarily responsible for glucose uptake in response to insulin in fat and muscle cells?

    <p>GLUT-4</p> Signup and view all the answers

    What happens to GLUT-4 transporters when insulin levels decrease?

    <p>They are recycled back into the cytoplasm.</p> Signup and view all the answers

    Which of the following tissues does not require insulin for glucose uptake?

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

    What is the primary function of insulin in relation to glycogen synthesis in the liver?

    <p>Insulin stimulates the storage of glucose in the form of glycogen.</p> Signup and view all the answers

    How does obesity affect insulin sensitivity in cells?

    <p>Obesity leads to insulin resistance in fat cells.</p> Signup and view all the answers

    What occurs in the liver when insulin is absent?

    <p>Enzymes responsible for glycogen breakdown become active.</p> Signup and view all the answers

    Which enzyme is activated by insulin to facilitate the trapping of glucose within liver cells?

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

    What is the primary effect of having more fat cells than muscle cells on insulin effectiveness?

    <p>Insulin becomes less effective, allowing glucose to remain in circulation.</p> Signup and view all the answers

    What characterizes Diabetes Mellitus primarily?

    <p>Hyperglycaemia and metabolic disturbances.</p> Signup and view all the answers

    What is a common consequence of insulin resistance in diabetic patients?

    <p>Overworking of the pancreas leading to potential failure.</p> Signup and view all the answers

    Which of the following is a symptom of chronic hyperglycaemia in diabetes?

    <p>Polydipsia.</p> Signup and view all the answers

    Which blood glucose level qualifies for a diagnosis of Diabetes Mellitus during a fasting plasma glucose test?

    <p>126 mg/dl (7.0 mmol/l).</p> Signup and view all the answers

    What long-term complications are associated with chronic hyperglycaemia?

    <p>Retinopathy and renal failure.</p> Signup and view all the answers

    What indicates the diagnosis of diabetes using a casual plasma glucose test?

    <p>200 mg/dl (11.1 mmol/l).</p> Signup and view all the answers

    What happens to red blood cells with excess glucose exposure in diabetes?

    <p>Glucose molecules get attached to them.</p> Signup and view all the answers

    What is the main feature distinguishing latent autoimmune diabetes in adults (LADA) from type 2 diabetes?

    <p>LADA is an autoimmune disease.</p> Signup and view all the answers

    Which of the following diseases can cause Type 3c diabetes?

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

    What is the role of cortisol in carbohydrate metabolism?

    <p>It preserves carbohydrate reserves.</p> Signup and view all the answers

    What percentage of the Jamaican population is affected by Type 2 diabetes?

    <p>15-20%</p> Signup and view all the answers

    How does human placental lactogen affect insulin resistance during pregnancy?

    <p>It blocks the uptake and use of glucose by tissues.</p> Signup and view all the answers

    What distinguishes Type 1 diabetes in terms of prevalence compared to other types?

    <p>It is less common than Type 2 diabetes.</p> Signup and view all the answers

    Which hormone increases glucose concentration in the bloodstream by breaking down glycogen?

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

    What is the primary physiological consequence of insulin resistance?

    <p>Reduced biological response to insulin</p> Signup and view all the answers

    What is one potential cause of insulin resistance related to the secretion of insulin?

    <p>Abnormal β cell secretory product</p> Signup and view all the answers

    Circulating insulin antagonists can be classified into which two categories?

    <p>Hormonal and non-hormonal</p> Signup and view all the answers

    What factor can hinder the action of insulin at target tissues?

    <p>Defect in any downstream effector systems from receptor binding</p> Signup and view all the answers

    How does elevated free fatty acids (FFA) influence insulin resistance?

    <p>Inhibits important enzymatic reactions like hexokinase action</p> Signup and view all the answers

    What is insulin sensitivity defined as?

    <p>The ability of β cells to adapt insulin secretion to blood glucose changes</p> Signup and view all the answers

    Defective secretion of which hormone can contribute to insulin resistance?

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

    What role does adiponectin play in the context of insulin sensitivity?

    <p>It functions in the homeostatic control of glucose and lipid metabolism.</p> Signup and view all the answers

    What can resolving elevated free fatty acids potentially affect?

    <p>Alleviate insulin resistance</p> Signup and view all the answers

    Study Notes

    Carbohydrate Metabolism Lecture 1

    • Course Information:
      • 8-10 multiple choice questions on the in-course test (October 2024).
      • Possibly 10-12 multiple choice questions on the final exam (December 2024).
      • 1 long answer question on the final exam from lectures (December 2024).

    Lecture Content

    • Carbohydrate Metabolism Overview:
      • Defining carbohydrate metabolism.
      • Importance of carbohydrate metabolism.
      • Is glycolysis the same as carbohydrate metabolism? (Question to consider).
      • Insulin's role in carbohydrate metabolism.
      • Major diseases associated with carbohydrate metabolism.

    Lecture Topics

    • Questions for the lecture:
      • What exactly is carbohydrate metabolism?
      • When carbohydrate metabolism goes abnormal, what are the consequences/pathologies?

    Summary

    • Central Role of Carbohydrates:
      • Carbohydrate metabolism is central to all metabolic pathways.
    • Metabolic Interdependence:
      • Disruptions in carbohydrate metabolism lead to issues in other metabolic pathways (fat and protein metabolism).
    • Diabetes Mellitus:
      • Diabetes Mellitus is strongly linked to problems with carbohydrate metabolism.

    Metabolism/Energy

    • Body's Energy Needs:
      • The body requires energy for life processes (brain and muscle function).
    • Energy Sources:
      • Energy comes from carbohydrates, proteins and fats.
    • Energy Storage and Use:
      • Excess energy is stored as fat, leading to potential obesity.
    • Metabolic Rate:
      • Metabolic rate measures caloric use.
    • Consequences of Inadequate Supply:
      • An insufficient energy supply causes system failure, leading to death.
    • Lactate Metabolism:
      • Lactate metabolism is an alternative energy source for cells in emergencies.

    Carbohydrates to Glucose

    • Digestion & Conversion:
      • Digestion changes carbohydrates into monosaccharides, which the liver converts to glucose.
    • Liver Function:
      • The liver is key for storing and distributing glucose throughout the body.
    • Glucose Metabolism:
      • Glucose is metabolized in peripheral tissues, primarily to produce ATP (energy).

    Carbohydrate Metabolism

    • Energy Production:
      • The breakdown of carbohydrates releases energy, primarily in the form of ATP.
    • Coupling Agent:
      • ATP acts as a coupling agent between different metabolic processes.
    • Energy Source:
      • Carbohydrates, particularly glucose, are crucial energy sources for organisms.

    Carbohydrates as Electron Donors

    • Energy Storage:
      • Metabolism involves storing energy as ATP.
    • Heat Production:
      • Metabolic reactions also produce heat.
    • Metabolic Equation:
      • Glucose metabolism results in ATP, carbon dioxide, and water.

    Fate of Glucose

    • Storage:
      • Glucose is stored as glycogen in the liver and muscles.
    • Fat Conversion:
      • Glucose can be converted to fatty acids and stored as triglycerides in adipose tissue.
    • Energy Production:
      • Glucose is broken down through glycolysis for ATP production.

    Biosynthesis of Insulin

    • Pancreatic Production:
      • Insulin is made in significant quantities by beta cells in the pancreas.
    • mRNA Translation:
      • Insulin mRNA is initially translated into a precursor molecule (pre-proinsulin).
    • Processing:
      • Signal peptides are removed, and the precursor undergoes further processing to form proinsulin and finally mature insulin.

    Mechanism of Insulin Secretion

    • Glucose Entry:
      • Glucose enters beta cells via GLUT-2 transporter.
    • Metabolism & ATP Production:
      • Glucose metabolism and ATP production cause changes in the beta cells.
    • Calcium Release:
      • Calcium channels open, leading to calcium influx that stimulates insulin release.

    Effect of Glucose Infusion

    • Initial Insulin Rise:
      • A glucose infusion leads to a fast insulin rise from already existing insulin.
    • Secondary Insulin Rise:
      • The level of newly synthesized insulin increases and is released immediately.

    Insulin Secretion

    • Electrical Activity Trigger:
      • Glucose triggers electrical activity in beta cells.
    • Glucose Transporter:
      • GLUT-2 is the glucose transporter in beta cells.
    • Obligate Step:
      • Glucose metabolism is a critical step for insulin secretion.

    Release of Insulin

    • Exocytosis:
      • Insulin is released from beta cells via exocytosis.
    • Membrane Fusion:
      • Insulin granule membranes fuse with the cell membrane.
    • Disruption and Release:
      • The membranes break down, releasing insulin into the extracellular space.

    Insulin and Regulation of Glucose Transport

    • Muscle and Fat Transport:
      • Insulin boosts glucose uptake by muscle and fat cells.
    • GLUT-4 Activity:
      • A glucose transporter protein (GLUT-4) is crucial for this uptake.
    • Sequestering of GLUT-4 in Absence of Insulin:
      • When insulin is low, GLUT-4 is stored within the cell to keep it out of the lipid membrane and out of action.

    Insulin and Regulation of Glucose Transport (continued)

    • Insulin Receptor Binding:
      • Insulin binding to receptors on target cells leads to glucose transporter movement.
    • Glucose Transporter Recycling:
      • When insulin levels fall, glucose transporters are transported back into the cell to be stored and used again when necessary.
    • Insulin-Independent Tissues:
      • Some tissues (e.g., brain and liver) do not depend on insulin for glucose uptake.

    Distribution of Glucose After a Meal

    • 90g of glucose and its distribution:
      • Diagram demonstrating glucose distribution after a meal (Liver, Fat, Muscle, Brain, Kidneys).

    Insulin and Regulation of Glycogen Synthesis

    • Liver Glycogen Storage Stimulation:
      • Insulin induces glycogen storage in the liver from circulating glucose.
    • Hexokinase Activation:
      • Hexokinase is activated to phosphorylate glucose, keeping it inside the cells.
    • Glycogen Synthesis:
      • Glucose is converted into glycogen (the storage form).

    Too Much Energy from Food and Diabetes

    • Overeating and Obesity Link:
      • Excessive food intake creates an obesity cycle, leading to insulin resistance and type 2 diabetes.
    • Metabolic Cycle:
      • The diagram shows the cycle of overeating, obesity, enlarged fat cells, and insulin resistance leading to type 2 diabetes.

    Obesity and Insulin Resistance

    • Association with Resistance:
      • Obesity is frequently connected to insulin resistance.
    • Insulin's Delivery Function:
      • Insulin moves glucose into cells.
    • Cellular Responsiveness:
      • Obesity makes cells less sensitive to insulin.
    • Fat Cell Resistance:
      • Fat cells are more resistant to insulin than muscle cells.

    High Glucose Levels and Diabetes Mellitus

    • Defining Characteristic:
      • Diabetes Mellitus is defined by excess glucose in the blood.
    • Metabolic Disturbances:
      • Excess glucose and disturbances in carbohydrate, fat, and protein metabolism are hallmarks of diabetes mellitus.
    • Impact of Insulin Deficiencies:
      • Absolute and relative insulin deficiency is linked to these disturbances.

    Obesity, Insulin Resistance, and Diabetes

    • Correlation with Obesity:
      • The rise in diabetes is directly linked to increasing obesity rates.
    • Prevalence in Overweight/Obese:
      • Most people with diabetes are overweight or obese.
    • Cellular Changes:
      • Excess weight creates cellular changes that cause insulin resistance.
    • Pancreatic Overwork:
      • Insulin resistance strains the pancreas leading to later pancreatic failure.

    Description of Diabetes Mellitus

    • Chronic Disorder:
      • Diabetes Mellitus is a chronic metabolic disorder.
    • Hyperglycemia State:
      • High blood sugar (hyperglycemia) in fasting or after eating is common in diabetes.
    • Organ Dysfunction:
      • Chronic hyperglycemia damages various organs (eyes, kidneys, nerves, heart, blood vessels).

    Diabetes Mellitus Description (cont'd)

    • Symptoms of Hyperglycemia:
      • Symptoms include polyuria, polydipsia, weight loss, and blurred vision.
    • Comorbidities:
      • Impaired growth and increased infection risk are associated with diabetes.
    • Long-Term Complications:
      • Chronic high blood sugar leads to severe complications including retinopathy (vision damage) and nephropathy (kidney failure).

    Determining Blood Glucose Levels

    • Diagnosis of Diabetes Criteria:
      • Casual plasma glucose concentration of 200 mg/dL (11.1 mmol/L) or higher with symptoms is used to diagnose diabetes mellitus.
    • Fasting Blood Glucose:
      • A fasting blood glucose level of 126 mg/dL (7.0 mmol/L) or higher is used to diagnose diabetes mellitus when a person has not had any food intake for at least eight hours.
    • Oral Glucose Tolerance Test (OGTT):
      • An oral glucose tolerance test (OGTT) involves measuring blood glucose after a load of sugar and it is assessed if the high blood glucose level exceeds 200 mg/dL (11.1 mmol/L) to diagnose diabetes mellitus .

    Diabetes Mellitus Diagnosis (cont'd)

    • Glycated Hemoglobin (HbA1c):
      • Testing the glycated hemoglobin (HbA1c) shows average blood glucose levels over the past 120 days which is used for diagnosing diabetes mellitus.
      • A HbA1c level of 6.5 mmol/L or higher indicates diabetes mellitus.

    Impaired Glucose Tolerance

    • Fasting Glucose Level:
      • Fasting glucose is greater than 6.1 mmol/L.
    • Postprandial Glucose Level:
      • Postprandial glucose is greater than 7.8 mmol/L.

    Types of Diabetes Mellitus

    • Type 1:
      • Formerly known as juvenile diabetes.
      • Characterized by Beta cell destruction due to an autoimmune process.
      • Often develops before age 25.
    • Type 2:
      • Also called adult-onset diabetes.
      • Characterized by insulin resistance and impaired insulin secretion.
      • Strongly linked to lifestyle factors like obesity and lack of exercise.
    • Gestational Diabetes:
      • Diagnosed during pregnancy.
      • Relative insulin deficiency usually resolves after pregnancy.
      • Significant risk factor for later developing type 2 diabetes.
    • Other Specific Types:
      • These types result from various causes (e.g., genetic defects, diseases).

    Counter-regulatory Hormones & Diabetes

    • Cortisol:
      • Preserves carbohydrate stores by promoting glucose production (gluconeogenesis).
      • Promotes protein breakdown.
      • Promotes fat breakdown.
      • Decreases glucose metabolism.
    • Glucagon:
      • Breaks down glycogen in the liver and muscles.
      • Increases glucose levels in the bloodstream.
      • Promotes gluconeogenesis.
    • Human Placental Lactogen:
      • Contributes to insulin resistance and increased circulating free fatty acids (FFAs).
      • Interferes with glucose use by peripheral tissues.

    Insulin Resistance

    • Reduced Response:
      • Insulin resistance is a state in which the body's response to insulin is reduced.
    • Glucose Disposal:
      • The inability of glucose to be taken up by cells to be used as energy.
    • Insulin Action Pathway:
      • Describes the path for insulin to travel through the circulatory system to the target tissue.

    Insulin Resistance (continued)

    • Causes of Insulin Resistance:
      • Abnormal beta-cell function.
      • Circulating insulin antagonists.
      • Target-tissue defects.
      • Defective adiponectin secretion.

    Insulin Resistance Causes (Specific)

    • Abnormal Beta Cell Product:
      • Defectively created insulin can cause resistance.
      • Incomplete conversion of proinsulin to insulin.
    • Circulating Insulin Antagonists:
      • Hormones (cortisol, glucagon).
      • Non-hormonal (antibodies).
    • Target Cell Defects:
      • Problems in the downstream pathways after insulin binding to the receptor can cause resistance.
    • Defective Adiponectin Secretion:
      • Adiponectin, a hormone secreted by fat cells plays a vital role in glucose metabolism and insulin sensitivity.

    Elevated Fatty Acids and Insulin Resistance

    • Uptake Inhibition:
      • Elevated free fatty acids (FFAs) inhibit the uptake of glucose by peripheral tissues (fat and muscle).
    • Enzyme Inhibition:
      • FFAs block enzymes crucial for glucose metabolism (e.g., hexokinase).
    • Glucose Level Increase:
      • High FFAs increase glucose in the bloodstream.
    • Insulin Resistance Development:
      • High levels of FFAs contribute to insulin resistance.

    Insulin Sensitivity

    • Definition:
      • Insulin sensitivity is the ability of cells to respond to insulin.
    • Regulation:
      • Prompt changes in insulin secretion are crucial for maintaining sensitivity.
    • Importance for Homeostasis:
      • Insulin sensitivity is essential for metabolic homeostasis.
    • Effect of Decreased Sensitivity:
      • Decreased sensitivity causes high blood glucose (hyperglycemia), leading to diabetes.

    Summary (Reiteration)

    • Carbohydrate Central Role:
      • Carbohydrate metabolism is fundamental for overall metabolic processes.
    • Disruptions and Consequences:
      • Disruptions in carbohydrate metabolism lead to problems in fat and protein metabolism.
    • Diabetes as a Result:
      • Diabetes Mellitus is the prominent disorder caused by problems in carbohydrate metabolism.

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    Related Documents

    BIOC2014 Carbohydrate Metabolism Lecture 1 PDF

    Description

    Explore the essential processes and roles of carbohydrate metabolism in the human body with this quiz. Test your knowledge on digestion, insulin function, and the metabolic pathways involved. Understand how carbohydrates influence athletic performance and overall health.

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