Glucose Metabolism Quiz

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Questions and Answers

What is the primary role of glucose in the body?

It is stored primarily as fat in adipose tissue.

It regulates hormonal balance in the liver.

It is the primary component of muscle tissue.

It serves as the main source of cellular energy. (correct)

Which hormone is most crucial for regulating blood glucose levels?

Glucagon

Epinephrine

Insulin (correct)

Cortisol

What is a common cause of hyperglycemia?

Increased glucose utilization

Diabetes mellitus (correct)

Excess insulin secretion

Decreased glycogen storage

Which condition is associated with hypoglycemia?

Insulinoma Signup and view all the answers

What is the significance of measuring glucose in urine?

It aids in the diagnosis of diabetes and renal defects. Signup and view all the answers

What is a potential consequence of pancreatitis related to glucose levels?

Hyperglycemia due to insulin deficiency Signup and view all the answers

Through which fluid is glucose measurement commonly used for evaluating neurological disorders?

Cerebrospinal fluid Signup and view all the answers

What test modification has been developed for glucose analysis in clinical chemistry?

Dipstick test Signup and view all the answers

What is the primary role of glucose oxidase in the determination of glucose levels?

It catalyzes the oxidation of glucose to gluconic acid. Signup and view all the answers

Which substance is produced when glucose is oxidized by glucose oxidase?

Hydrogen Peroxide Signup and view all the answers

Which reaction is coupled with glucose oxidase for visualizing glucose levels colorimetrically?

Peroxidase-catalyzed reaction with o-dianisidine Signup and view all the answers

What is the significance of measuring the intensity of pink color at 540 nm?

It is proportional to the glucose concentration. Signup and view all the answers

What type of enzyme is glucose oxidase classified as?

Oxido-reductase Signup and view all the answers

In which application is glucose oxidase widely used?

Monitoring glucose levels in diabetics Signup and view all the answers

What role does sulfuric acid play in the glucose oxidation reaction described?

It stabilizes the oxidized o-dianisidine product. Signup and view all the answers

How do enzyme electrode biosensors detect glucose levels?

By tracking the number of electrons transferred. Signup and view all the answers

What should be done if turbidity develops in the glucose stock solution?

Discard the solution. Signup and view all the answers

What is the purpose of making each standard glucose solution in triplicate?

To ensure accuracy and reliability of the results. Signup and view all the answers

How much of unknown solution should be used in each test tube?

500 ul Signup and view all the answers

At what temperature and duration should the mixture be incubated?

37°C for 15 minutes Signup and view all the answers

What is measured to determine the concentration of glucose in the unknown solution?

Absorbance at 540 nm Signup and view all the answers

What is the concentration range for the standard glucose solutions prepared?

5-25 ug/ml Signup and view all the answers

What reagent is added to each test tube to initiate the glucose assay?

Glucose oxidase-peroxidase (GOD-POD) reagent Signup and view all the answers

How should the glucose stock solution be stored for optimal stability?

At 2–8°C Signup and view all the answers

What is the maximum stability duration of the solution at 2–8°C?

1 month Signup and view all the answers

What should be done if turbidity develops in the solution?

Discard it Signup and view all the answers

How should O-Dianisidine reagent be prepared?

Dissolve 5mg in 1.0 ml of 50% ethanol Signup and view all the answers

What temperature should the O-Dianisidine reagent be stored at for maximum stability?

2–8°C Signup and view all the answers

What is the incubating temperature and duration for the GOD-POD assay?

37°C for 15 minutes Signup and view all the answers

What is the purpose of adding 500 µl of 12N H2SO4 in the procedure?

To stop the reaction Signup and view all the answers

What is the ideal volume of unknown solution to be used in the test tubes?

500 µl Signup and view all the answers

How is the standard glucose solution prepared for the assay?

Using potassium phosphate buffer at pH 7.0 Signup and view all the answers

What is the primary advantage of the Trinder method over the original method using o-dianisidine?

It replaces o-dianisidine with safer reagents. Signup and view all the answers

Which of the following reagents is stable for at least six months when stored at 2-8°C?

Glucose stock solution Signup and view all the answers

What is the purpose of the glucose oxidase and peroxidase in the GOD-POD reagent?

To catalyze the oxidation of glucose. Signup and view all the answers

Why is it important to minimize exposure to light when handling the reagents?

It avoids chemical reactions that can degrade the reagents. Signup and view all the answers

What specific temperature range is suggested for storing the GOD-POD reagent?

2°C to 8°C Signup and view all the answers

What is the role of 4-aminoantipirine in the glucose estimation process?

It replaces the carcinogenic component. Signup and view all the answers

How should the o-dianisidine reagent be prepared for use?

Dissolving in 50% ethanol. Signup and view all the answers

What occurs if turbidity develops in the glucose stock solution?

It should be discarded. Signup and view all the answers

Study Notes

Glucose Metabolism and Regulation

Glucose oxidation is the main energy source in the body
Dietary glucose is stored as glycogen in the liver or as fatty acids in adipose tissue
Blood glucose concentration is tightly regulated by hormones, mainly insulin
Hyperglycemia is most commonly caused by diabetes mellitus, due to insulin deficiency or resistance

Hypoglycemia

Less frequent than hyperglycemia
Causes include insulinoma, hypopituitarism, or insulin-induced hypoglycemia

Glucose Measurement in Urine

Used as a diabetes screening test
Involves measuring glucose levels in urine to assess for glucosuria, renal tubular defects, and to manage diabetes mellitus

Glucose Measurement in Cerebrospinal Fluid

Used for evaluating meningitis, neoplastic involvement of meninges, and various neurological disorders

Enzymatic Glucose Analysis

Widely used in clinical chemistry for analyzing glucose in blood and urine
Dipstick tests utilize glucose oxidase, coupled with peroxidase reaction
The reaction visualizes the formed H2O2 colorimetrically
Used in diagnostics, using spectrometric assays (manual or automated)
Used in monitoring glucose levels in fermentation, bioreactors, and to control glucose content in vegetal raw materials and food products

Biosensors

Enzyme electrode biosensors detect glucose by tracking electrons passed through the enzyme, connected to an electrode and measuring the resulting charges
Possible application in nanotechnology, using tiny electrodes as glucose sensors for diabetics

Principle of Glucose Analysis

Glucose is oxidized to gluconic acid, and molecular oxygen is reduced to hydrogen peroxide by glucose oxidase
Hydrogen peroxide reacts with o-dianisidine in the presence of peroxidase enzyme to form oxidized o-dianisidine, which then reacts with sulfuric acid to produce a stable colored product
The intensity of the pink color measured at 540 nm is directly proportional to the original glucose concentration
Glucose oxidase, an oxido-reductase, catalyzes the oxidation of glucose to D-glucono-δ-lactone, reducing molecular oxygen to hydrogen peroxide
In cells, it aids in breaking down sugar into its metabolites

Historical Evolution of Glucose Determination

Enzymatic methods for glucose determination were first described in 1948 by Keilin and Hartee using glucose oxidase in a manometric technique
Keston modified this method in the early 1950s using glucose oxidase/peroxidase enzyme system and o-dianisidine chromogen system
The Trinder method replaced carcinogenic o-dianisidine with phenol plus 4-aminoantipirine

Reagents Required

Glucose Stock: 200 µg/ml solution in 20 mM potassium phosphate (pH 7.0) buffer, stable at 2-8°C for at least six months
GOD-POD Reagent: 500 units of glucose oxidase, 100 units of peroxidase dissolved in 39.2 ml of 20 mM potassium phosphate (pH 7.0) buffer, stable up to one month at 2-8°C and for at least 6 months frozen at -20°C
o-Dianisidine Reagent: 5 mg of o-dianisidine dissolved in 1.0 ml of 50% ethanol, stable for 3 months at 2-8°C
GOD-POD Assay Reagent: 0.8 ml of o-Dianisidine reagent added to the bottle containing 39.2 ml of GOD-POD Reagent, stable for 1 month at 2-8°C

Procedure

Prepare five standard glucose solutions (5-25 µg/ml) using 20 mM potassium phosphate (pH 7.0) buffer
Make each standard glucose solution in triplicate, with 500 µl volume in each test tube
Use 500 µl of 20 mM potassium phosphate pH 7.0 solutions for blank (duplicates are sufficient)
Use 500 µl of unknown solution in triplicate
Add 500 µl of GOD-POD assay reagent to each test tube, including the blanks
Mix well and incubate for 15 min at 37°C using a hot air oven
Add 500 µl of 12N H2SO4 to each test tube and mix well
Measure the absorbance of the pink color at 540 nm using a plastic cuvette
Draw a standard curve and calculate the amount of glucose present in the unknown solution

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Description

Test your knowledge on glucose metabolism and regulation. This quiz covers glucose oxidation, storage, measurement in urine and cerebrospinal fluid, and causes of hypoglycemia and hyperglycemia. Perfect for students of biochemistry and medicine.