Quantitative Determination of Glucose in Biochemistry

What is the primary function of insulin in relation to glucose?

Which type of diabetes is characterized by an inability to produce or secrete insulin?

What is the role of glucose oxidase (GOD) in glucose determination?

In the procedure, what is the appropriate wavelength for reading absorbance?

What additional component is needed for the reaction of hydrogen peroxide with phenol in the glucose assay?

How long should the color formed during the assay be stable for reading absorbance?

What is the purpose of adjusting the instrument to zero with a reagent blank?

What does the intensity of the color formed during the glucose reaction indicate?

What is the normal range for blood glucose concentration in plasma/serum?

Which of the following conditions can cause hyperglycemia?

What is the formula used to calculate the concentration of glucose in mg/dl?

What is the maximum acceptable blood glucose level for a diabetic patient before a meal for tooth extraction?

How does high blood glucose affect wound healing?

Which of the following is NOT a cause of hypoglycemia?

Glucose Overview

Glucose is a major source of energy for most cells.
Insulin facilitates glucose entry into cells.
Diabetes (hyperglycemia) results from an inability of insulin to be produced or secreted.

Types of Diabetes

Insulin-dependent diabetes mellitus (IDDM)
Non-Insulin-dependent diabetes mellitus (NIDDM)
Gestational diabetes
Diabetes insipidus

Glucose Oxidase (GOD) Principle

GOD catalyzes the oxidation of glucose to gluconic acid.
Hydrogen peroxide (H2O2) is detected by a chromogenic oxygen acceptor, phenol, 4-aminophenazone (4-AP) in the presence of peroxidase (POD).
The intensity of the color formed is proportional to glucose concentration in the sample.

Assay Conditions

Wavelength: 546nm (490-550)
Cuvette: 1cm light path
Temperature: 37ºC or 15-25ºC
Adjust the instrument to zero with reagent blank

Procedure

Pipette into a cuvette:
- Blank: 1.0 ml R2
- Standard: 1.0 ml R2, 10 µl standard
- Sample: 1.0 ml R2, 10 µl sample
Mix and incubate for 10 min at 37ºC or 30 min at room temperature (15-25ºC)
Read the absorbance (A) of the samples and standard, against the blank

Calculation

Concentration of glucose (mg/dl) = A Sample / A Standard * 100 (standard conc.)
1 mg/dl = 0.0555 mmol/L

Expected Value

Plasma, serum: 60-110 mg/dl (~ 3.33-6.1 mmol/L)

Clinical Significance

Causes of hyperglycemia:
- Pancreatitis
- Diabetes mellitus
- Obesity
- Acromegaly
- Hyperthyroidism
- Cushing's syndrome
- Administration of certain drugs
Causes of hypoglycemia:
- Insulinemia
- Addison's disease
- Galactosemia
- Alcohol ingestion
- Severe liver disease

Dental Treatment

Maximum acceptable levels of blood glucose for removal of teeth in diabetics:
- 180 mg/dl (before meal)
- 234 mg/dl (2 h after a meal)
High blood glucose levels reduce nitric oxide secretion, leading to poor circulation and slow-healing sockets.

Learn about the importance of glucose, insulin, and diabetes in biochemistry. Understand how dietary carbohydrates are digested and absorbed, and how blood glucose concentration is regulated.