Protein that precipitates on heating to 45° C and redissolves on boiling is –
**Question:** Protein that precipitates on heating to 45° C and redissolves on boiling is -
A. Albumin
B. Globulin
C. Glycoproteins
D. Immunoglobulins
**Core Concept:** Proteins are complex organic molecules made up of amino acids. They perform various functions in the body, such as enzymes, hormones, antibodies, and transporting substances like iron and glucose. Proteins can undergo conformational changes upon heating, which leads to precipitation or solubility.
**Why the Correct Answer is Right:** The correct answer, D. Immunoglobulins, refers to a class of proteins that are part of the body's immune system. These proteins, specifically antibodies, are responsible for recognizing and neutralizing foreign substances like bacteria and viruses. When heated to 45° C, immunoglobulins precipitate due to their high molecular weight and complex structure. When heated further to boiling (100° C), these proteins undergo denaturation, which reverses the conformational changes, making them soluble again.
**Why Each Wrong Option is Incorrect:**
A. Albumin (Correct Answer D) is a different type of protein, primarily involved in maintaining osmotic pressure and fluid balance within the body. Heating to 45° C does not cause precipitation of albumin because it has a lower molecular weight and simpler structure compared to immunoglobulins.
B. Globulins are a group of proteins that include immunoglobulins and other proteins, such as enzymes and hormones. However, unlike immunoglobulins, globulins do not exhibit specific precipitation at 45° C.
C. Glycoproteins are proteins modified with sugar molecules (glycosylation). Although heating can affect protein structure and function, the specific precipitation at 45° C is not a characteristic of glycoproteins.
**Clinical Pearl:** The phenomenon of protein precipitation and solubility upon heating has implications in laboratory testing, particularly in serology. Knowing the different protein types and their thermal stability can help interpret test results accurately and avoid misinterpretation of findings.