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Globin and Globulin

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Overview

The article gives information about the proteins like globin and globulin. After reading this article, the reader will learn about:


  • The differences between globin and globulin

  • Functions of globin and globulin

  • Examples of globin and globulin

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What is Globin?

A superfamily of globular proteins with a heme group is called the protein known as globin. So, the primary function of globins is to transfer or bind oxygen. Myoglobin and haemoglobin are the two main types of globins in the body. The oxygen-binding protein in vertebrate muscles is known as myoglobin, while the oxygen-transporting metalloprotein in vertebrate red blood cells is haemoglobin. Furthermore, certain invertebrate tissues may also contain globins. Furthermore, a heme prosthetic group that reversibly binds to oxygen is present in each of these proteins.


Additionally, the globin fold, made up of a sequence of eight alpha-helical segments, is the primary structural component of all known globins. Additionally, this fold has three dimensions. But these eight helices are connected at the core by a particular nonlocal structure. In this particular form, amino acids are typically found adjacent to one another in both their core structure and the surrounding space. Also, the packing angle is typically 50 degrees. Androglobin, globin E, globin X, globin Y, cytoglobin, and neuroglobin are the other six globin subtypes in vertebrates.


What is Globulin?

The globulins are a class of globular proteins insoluble in pure water but dissolve in diluted salt solutions. They have greater molecular weights than albumins. While the immune system generates some globulins, others are made in the liver. The three main blood proteins are fibrinogen, albumins, and globulins. About 2.6 to 3.5 g/dL of globulins are typically present in human blood. Sometimes "globulin" and "globular protein" are used interchangeably.


Albumins are globular proteins as well, but they are not globulins. Globulins are all other serum globular proteins. The essential functions of globulins are to maintain proper liver functioning, help blood clotting, and fight off infections caused by pathogens.


Alpha 1 globulins, alpha 2 globulins, beta globulins, and gamma globulins are the four types of globulins. Immunoglobulins, often known as antibodies, are a class of gamma globulins. Additionally, among globulins, alpha globulins have the lowest molecular weight. They have a molecular mass of around 93 kDa. Gamma globulins have a molecular weight of around 1193 kDa and have the largest molecular weight. Furthermore, the two globulin types found in beans are vicilin and legumin, which perform the role of storage proteins.


Similarities Between Globins and Globulins

  • Both Globin and Globulin are globular proteins present in the blood plasma.

  • They both are soluble in water but under slightly different conditions.

  • These proteins carry out their major functions in metabolic activity and primarily in the blood.


Differences Between Globins and Globulins

Let’s look at the difference between globins and globulins.



Globins

Globulins

Definition

Globin refers to a superfamily of heme-containing globular proteins that are in charge of binding and transporting oxygen.

Globulin refers to a family of simple proteins that are soluble in salt solutions and make up a significant portion of the proteins in blood serum.

Functions

The primary role of globins is to bind and/or transport oxygen.

Globulins are serum proteins produced by the immune system and the liver, which help in blood clotting and fights off infection.

Molecular weight

Molecular weight of globins is around 16 kDa.

Molecular weight of globulins is around 100-1000 kDa.

Solubility

Globins are soluble in water.

Globulins are insoluble in pure water but soluble in dilute salt solutions.

Examples

Myoglobin and Haemoglobin.

Alpha globulins, Beta globulins and Gamma globulins.


Interesting Facts

  • Four heme groups surround a globin group in each haemoglobin molecule. Iron is present in heme, which gives the molecule its red colour. Two linked pairs of polypeptide chains make up globin.

  • Serum protein electrophoresis can be used to separate globulins from one another.


Important Questions

1. What is alpha globulin?

A class of globular plasma proteins known as alpha globulins are very mobile in alkaline or electrically charged solutions. They have strong inhibitory efficacy and inhibit several blood proteases. Molecular weights for alpha globulins are generally about 93 kDa. Certain hormones, hormone-transporting proteins, and other substances, including prothrombin and HDL (High-Density Lipoprotein), are included in alpha globulins.


2. What is the major difference between Globins and Globulins?

The primary distinction between globin and globulin is that the former is a superfamily of globular proteins that include heme, while the latter is a family of globular proteins with larger molecular weights.


Conclusion

A group of blood proteins with a smaller molecular weight is known as globins. They are also the structural building blocks of myoglobin and haemoglobin. As a result, globins' primary role is to bind to and transport oxygen. Whereas, the blood contains globulin, a form of globular protein. In contrast to albumins, they have a larger molecular weight. Additionally, they have an immunological role in the body. Thus, the primary distinction between globin and globulin is based on their function and molecular weight.


Practice Questions

1. How many oxygen molecules can a haemoglobin molecule carry?

a. 1 molecule

b. 2 molecules

c. 3 molecules

d. 4 molecules


2. Which of the following is a plant-based globulin?

a. Legumin

b. Beta globulin

c. Gamma globulin

d. None of the above


Answer:

1. (d)


2. (a)

Last updated date: 28th Sep 2023
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FAQs on Globin and Globulin

1. Write a note on Haemoglobin.

The oxygen-carrying pigment and main protein found in red blood cells is haemoglobin. The bond between oxygen and haemoglobin is weak and reversible. Its name is oxyhemoglobin, and it is a vivid red colour when it is oxygenated. Deoxyhemoglobin, which is purple-blue in its reduced form. Four heme groups surround a globin group in each haemoglobin molecule.


Iron is present in heme, which gives the molecule its red colour. Two linked pairs of polypeptide chains make up globin. Changes in the amino acid sequence of these chains cause anomalies in haemoglobins. Haemoglobin S, for instance, is present in sickle-cell anaemia, a severe form of anaemia in which the red blood cells take on the sickle shape when oxygen levels are low.

2. What is Serum Protein Electrophoresis?

Serum Protein Electrophoresis is an electrophoresis technique used to examine the globulin protein in the blood serum. In this technique, blood serum is applied to an acetate membrane soaked in a liquid buffer, to a buffered agarose gel matrix, or into liquid in a capillary tube, and exposed to an electric current to separate the serum protein components into five major fractions by electrical charge and size: serum albumin, alpha-1 globulins, alpha-2 globulins, beta 1 and 2 globulins, and gamma globulins.

3. What is the importance of Serum Protein Electrophoresis and A/G ratio test?

A serum protein electrophoresis test is most frequently performed to diagnose or monitor, a monoclonal gammopathy of unknown significance (MGUS), multiple myeloma, or to further explore a discrepancy between low albumin and a reasonably high total protein level. Additionally, multiple myeloma symptoms, unexplained bone pain, anaemia, proteinuria, chronic renal disease, and hypercalcemia are the other diseases diagnosed by Serum protein electrophoresis (SPE) test.


The albumin/globulin (A/G) ratio test measures your blood's overall protein content. This test is used to diagnose nutritional diseases and diseases related to the kidneys and liver.


Overview

The article gives information about the proteins like globin and globulin. After reading this article, the reader will learn about:


  • The differences between globin and globulin

  • Functions of globin and globulin

  • Examples of globin and globulin


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