Question

Proteoglycan present in the glomerular basement membrane is?

• A. Keratan sulphate 1
• B. Keratan sulphate 2
• C. Heparan sulphate
• D. Chondroitin sulphate

Answer 1

The Correct Option is C

The proteoglycan present in the glomerular basement membrane is Heparan sulphate.

To understand why Heparan sulphate is the correct answer, it's important to comprehend the role of proteoglycans within the glomerular basement membrane (GBM):

• Structure and Function of the GBM: The GBM is a key component of the kidney's filtration barrier. It is a dense network composed of a variety of molecules including proteins and proteoglycans.
• Role of Proteoglycans: Proteoglycans are a subtype of glycoproteins characterized by their carbohydrate chains called glycosaminoglycans (GAGs), which are extensively sulfated. These molecules contribute significant electrostatic properties to the GBM, essential for size and charge-selective filtration.
• Why Heparan Sulphate? Among the proteoglycans, Heparan sulphate is predominant in the GBM. Its numerous sulfate groups give it a high negative charge, playing a vital role in preventing negatively charged molecules, such as albumin, from passing through, thus maintaining proper filtration function.
• Comparison with Other Options:
  • Keratan sulphate 1 and 2: These are forms of keratan sulfate, which are less prevalent in the GBM compared to Heparan sulphate and are usually found in cartilage, the cornea, and other tissues.
  • Chondroitin sulphate: This proteoglycan is also a component of cartilage and not significantly present in the GBM.

Therefore, the predominant proteoglycan contributing to the unique properties of the glomerular basement membrane is Heparan sulphate.