Understanding Carbohydrates and Their Classification

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Questions and Answers

Which enzyme is deficient in von Gierke's disease?

  • Brancher enzyme
  • Glucose-6-phosphatase (correct)
  • Debrancher enzyme
  • a-1,4-glucosidase

What clinical feature is associated with Pompe's disease?

  • Hypoglycemia and mental retardation (correct)
  • Severe fasting hypoglycemia
  • Progressive liver enlargement
  • Absence of storage glycogen

What enzyme deficiency characterizes Forbe's disease?

  • Brancher enzyme
  • Debrancher enzyme (correct)
  • Glucose-6-phosphatase
  • C-Peptide

How much does whole blood glucose decrease per hour at room temperature?

<p>10 mg/dL (C)</p> Signup and view all the answers

What is the plasma glucose concentration at which glucagon and other glycemic factors are released?

<p>65-70 mg/dL (B)</p> Signup and view all the answers

Which type of symptoms are associated with neurogenic/adrenergic hypoglycemia?

<p>Tremors and palpitations (B)</p> Signup and view all the answers

What is the fasting requirement for assessing blood glucose levels?

<p>10-16 hours (A)</p> Signup and view all the answers

Which of the following is a characteristic of Andersen's disease?

<p>Unbranched amylopectin storage (D)</p> Signup and view all the answers

What is a characteristic symptom of Cushing syndrome?

<p>Excessive cortisol (A)</p> Signup and view all the answers

What condition is characterized by glucose intolerance that begins during pregnancy?

<p>Gestational diabetes mellitus (B)</p> Signup and view all the answers

Which laboratory finding would you expect in a state of hyperglycemia?

<p>Ketonemia (B)</p> Signup and view all the answers

What is the fasting plasma glucose threshold indicating provisional diabetes diagnosis?

<p>FPG ≥126 mg/dL (B)</p> Signup and view all the answers

What does the HbA1c measurement assess over a period of about 60 days?

<p>Long-term glucose control (C)</p> Signup and view all the answers

Which method separates glycated proteins based on chemical structure?

<p>Affinity chromatography (C)</p> Signup and view all the answers

In the Nelson Somogyi method, what is the end product produced indicative of glucose measurement?

<p>Arsenomolybdenum blue (A)</p> Signup and view all the answers

What is the primary disadvantage of the Glucose Oxidase Method?

<p>It is inhibited by high concentrations of several substances. (A)</p> Signup and view all the answers

Which reagent is used in the Dubowski method to measure glucose levels in urine and CSF?

<p>Glacial acetic acid (B)</p> Signup and view all the answers

What does the Hexokinase method quantify to determine glucose concentration?

<p>NADH formation (B)</p> Signup and view all the answers

Which hormone is elevated in pheochromocytoma?

<p>Epinephrine (B)</p> Signup and view all the answers

Which ketone body comprises the largest percentage in the body?

<p>β-hydroxybutyric acid (A)</p> Signup and view all the answers

What is indicated by C-peptide levels greater than 1:1 in a patient?

<p>Excessive insulin production (A)</p> Signup and view all the answers

What is the recommended specimen type for ketone measurement in diabetic patients?

<p>Fresh serum or urine (C)</p> Signup and view all the answers

Which of the following is not a cause of increased ketone levels?

<p>Lactose intolerance (A)</p> Signup and view all the answers

What does the Glucose Dehydrogenase Method measure?

<p>NADH generation (B)</p> Signup and view all the answers

What is the recommended situation for measuring ketones in Type 1 Diabetes patients?

<p>During acute illness or stress (C)</p> Signup and view all the answers

Which of the following methods is generally accepted as the reference method for glucose measurement?

<p>Hexokinase Method (D)</p> Signup and view all the answers

What is the general formula for a carbohydrate?

<p>Cx(H2O)y (A)</p> Signup and view all the answers

Which type of carbohydrate has a terminal carbonyl group?

<p>Aldose (B)</p> Signup and view all the answers

Which of the following is a characteristic of reducing sugars?

<p>Can reduce other compounds (A)</p> Signup and view all the answers

What determines the classification of oligosaccharides?

<p>Number of sugar units (D)</p> Signup and view all the answers

Which of the following is an example of a disaccharide?

<p>Maltose (A)</p> Signup and view all the answers

Which carbohydrate classification mainly focuses on whether the compound can exist in non-superimposable forms?

<p>Stereochemistry (B)</p> Signup and view all the answers

Trioses are classified as carbohydrates with how many carbon atoms?

<p>Three (D)</p> Signup and view all the answers

Which of the following carbohydrates yield more than 10 monosaccharides upon hydrolysis?

<p>Polysaccharides (A)</p> Signup and view all the answers

What characteristic defines non-reducing substances?

<p>No free anomeric carbon (A)</p> Signup and view all the answers

Which enzyme is responsible for converting disaccharides to monosaccharides in the intestine?

<p>Maltase (A)</p> Signup and view all the answers

What is a direct end product of glycolysis?

<p>Pyruvic acid (A)</p> Signup and view all the answers

What type of metabolic pathway is glycolysis classified as?

<p>Both aerobic and anaerobic (C)</p> Signup and view all the answers

Which enzyme deficiency is most commonly associated with galactosemia?

<p>Galactose-1-phosphate uridyl transferase (D)</p> Signup and view all the answers

What is a diagnostic indicator of essential fructosuria?

<p>Presence of fructose in urine (A)</p> Signup and view all the answers

What clinical feature is associated with hereditary fructose intolerance?

<p>Irritability and lethargy (C)</p> Signup and view all the answers

What condition occurs due to a defect in fructose-1,6-biphosphate?

<p>Hypoglycemia and lactic acidosis (D)</p> Signup and view all the answers

Flashcards

Carbohydrate general formula

Cx(H2O)y, where x and y are integers; CxHyOz.

Monosaccharides

Simple sugars that cannot be broken down into simpler sugars.

Disaccharides

Two monosaccharides joined by a glycosidic linkage.

Reducing sugars

Sugars with a free anomeric carbon that can reduce other compounds.

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Aldose

A type of monosaccharide with a terminal carbonyl group (aldehyde).

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Ketose

A type of monosaccharide with a middle carbonyl group (ketone).

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Glycosidic linkage

A covalent bond that links two monosaccharides to form a disaccharide or polysaccharide.

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Polysaccharides

Long chains of monosaccharides.

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Non-reducing sugars

Sugars that do not have a free aldehyde or ketone group and cannot reduce other compounds.

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Glycolysis

A metabolic pathway that breaks down glucose into pyruvate, producing ATP and NADH.

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Galactosemia

A genetic disorder affecting galactose metabolism, often causing infant health issues.

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Essential fructosuria

A genetic disorder causing fructose to be present in the urine due to a deficiency in the enzyme fructokinase.

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Hereditary fructose intolerance

A genetic disorder impairing fructose metabolism in liver, kidney and intestine, leading to severe symptoms.

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Fructose-1,6-biphosphate deficiency

A genetic disorder affecting fructose-1,6-biphosphate, leading to issues in glucose production.

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Amylase

An enzyme that breaks down complex carbohydrates into smaller sugars.

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Von Gierke's Disease

A glycogen storage disease caused by a deficiency in glucose-6-phosphatase, leading to severe fasting hypoglycemia, lactic acidosis, and glycogen accumulation in organs.

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Pompe's Disease

A glycogen storage disease caused by a deficiency in α-1,4-glucosidase, resulting in glycogen accumulation, particularly in muscle tissue.

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Forbe's Disease

A glycogen storage disease characterized by a deficiency in the debrancher enzyme, leading to glycogen accumulation and liver enlargement.

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Andersen's Disease

A glycogen storage disease caused by a lack of the brancher enzyme, leading to unbranched glycogen accumulation.

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Hypoglycemia

A condition characterized by abnormally low blood glucose levels, typically below 65-70 mg/dL.

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Neurogenic Hypoglycemia Symptoms

Symptoms of hypoglycemia related to the nervous system, including tremors, palpitations, anxiety, and sweating.

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Neuroglycopenic Hypoglycemia Symptoms

Symptoms of hypoglycemia related to the brain's lack of glucose, including dizziness, tingling, blurred vision, confusion, and behavioral changes.

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72-hour Fast Test

A diagnostic test for hypoglycemia involving a 72-hour fast with glucose, insulin, C-peptide, and proinsulin levels measured every 6 hours.

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Glucose Oxidase Method

A method for measuring glucose in CSF that involves the enzyme glucose oxidase. It's commonly used but can be inhibited by substances like uric acid, vitamin C, and bilirubin.

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Hexokinase Method

The reference method for measuring glucose, considered more accurate than oxidase methods. It's based on the enzyme hexokinase and involves measuring the formation of NADPH.

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Ketone Bodies

Molecules produced by the liver when the body needs energy from stored fat, especially during low carbohydrate availability.

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Ketonemia

High levels of ketone bodies in the blood.

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Ketonuria

Presence of ketone bodies in the urine.

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What are some causes of increased ketone levels?

High ketone levels can be caused by diabetes mellitus, starvation, high-fat diets, prolonged vomiting, and glycogen storage diseases.

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Why are ketone levels measured in Type 1 Diabetes?

Measuring ketone levels is recommended for patients with Type 1 Diabetes during acute illness, stress, pregnancy, or elevated blood glucose levels, as it can indicate ketoacidosis.

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What specimen is used for Ketone testing?

Fresh serum or urine is used for ketone testing; the urine sample should be tightly stoppered and analyzed immediately.

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Cushing syndrome

A hormonal disorder characterized by excess cortisol production, leading to various symptoms like weight gain, high blood pressure, and muscle weakness.

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Pheochromocytoma

A tumor in the adrenal gland that produces excessive epinephrine and norepinephrine, causing high blood pressure, rapid heart rate, and anxiety.

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Acromegaly

A hormonal disorder characterized by excess growth hormone, leading to enlarged hands, feet, and jaw.

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Gestational diabetes mellitus (GDM)

A condition where glucose intolerance develops during pregnancy, often due to hormonal changes.

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Diabetes symptoms

Symptoms of diabetes include increased thirst, frequent urination, excessive hunger, weight loss, fatigue, blurred vision, and slow-healing sores.

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Fasting plasma glucose (FPG)

A measure of blood glucose levels after an overnight fast, used to diagnose diabetes, impaired fasting glucose, or normal glucose levels.

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Glycosylated hemoglobin (HbA1c)

A blood test that measures the average blood sugar level over the past 2-3 months, indicating long-term blood sugar control.

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Microalbuminuria

The presence of small amounts of protein in the urine, an early sign of kidney damage in diabetic patients.

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C-peptide

A peptide that is released along with insulin from the pancreas, reflecting how well the pancreas is producing insulin.

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Folin-Wu method

A chemical method for measuring ALL REDUCING SUBSTANCES in the blood using Cupric ion reduction and phosphomolybdic acid as a reagent.

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Study Notes

Carbohydrates

  • Carbohydrates are compounds containing C, H, and O.
  • General formula: Cx(Hâ‚‚O)y
  • All carbohydrates contain C=O and -OH functional groups.
  • Derivatives may have additional chemical groups like phosphates, sulfates, and amines.
  • Models include Fischer and Haworth projections.

Classification of Carbohydrates

  • Based on the size of the carbon chain:
    • Trioses (3 carbons)
    • Tetroses (4 carbons)
    • Pentoses (5 carbons)
    • Hexoses (6 carbons)
  • Based on the position of the carbonyl group:
    • Aldoses (aldehyde group at the end)
    • Ketoses (ketone group in the middle)
  • Based on the number of sugar units:
    • Monosaccharides (cannot be broken down further)
    • Disaccharides (2 monosaccharides joined)
    • Oligosaccharides (2-10 monosaccharides joined)
    • Polysaccharides (many monosaccharides joined)
  • Examples of monosaccharides include glucose, fructose, and galactose.
  • Examples of disaccharides include maltose, lactose, and sucrose.
  • Examples of polysaccharides include starch and glycogen.

Chemical Properties of Carbohydrates

  • Reducing Sugars: Contain a ketone or aldehyde group, with a free anomeric carbon. They can reduce other compounds. Glucose, maltose, fructose, lactose, and galactose are examples.
  • Non-Reducing Sugars: Do not have a free anomeric carbon or a ketone or aldehyde group. Sucrose (table sugar) is an example.

Major Metabolic Pathways

  • Glycogenesis: Conversion of glucose to glycogen for storage.
  • Glycogenolysis: Breakdown of glycogen to glucose.
  • Hexose Monophosphate Shunt (HMP): Converts glucose-6-phosphate, creating NADPH and pentose phosphates.

Diabetes Mellitus

  • A group of metabolic diseases characterized by hyperglycemia (high blood sugar).
  • Glucosuria occurs when plasma glucose exceeds 180 mg/dL.
  • Ketosis develops with excessive Acetyl-CoA synthesis.
  • Hyperglycemia results from hormone imbalances.

Types of Diabetes

  • Type 1 Diabetes (possibly autoimmune and insulin dependent)
  • Type 2 Diabetes (possibly insulin resistant)
  • Gestational Diabetes Mellitus (GDM)(occurs during pregnancy)

Criteria and Points of Difference

  • Detailed information about the types of diabetes based on various medical criteria.

Specimen Collection and Handling

  • Fasting plasma glucose is typically higher in the morning.
  • Normal fasting glucose for serum/plasma is 70-110 mg/dL.
  • Arterial/capillary glucose is about 5 mg/dL higher than venous glucose when fasting.
  • Urine glucose analysis needs preservative and 4°C storage to prevent loss.
  • CSF glucose analysis requires centrifugation, 4°C-20°C storage if delayed, and normal CSF glucose is roughly 60-70% of plasma glucose.
  • The renal threshold for glucose is 180 mg/dL

Glucose Metabolism

  • Various tests for diagnosing, and long-term control of glucose metabolism are discussed in detail. (Includes various methods of testing blood glucose, and HbA1c)

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