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
Key Characteristics of Globin and Globulin Proteins
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.
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)
FAQs on Difference Between Globin and Globulin
1. What is the main difference between globin and globulin?
The main difference lies in their specificity and function. Globin is a specific type of protein that is a component of haemoglobin and myoglobin, primarily responsible for oxygen transport. In contrast, globulin is a broad category of proteins found in blood plasma, with diverse functions including transport, enzymatic activity, and immunity.
2. What is the specific function of the globin protein within haemoglobin?
Within the haemoglobin molecule, the globin portion consists of four polypeptide chains. The primary function of these chains is to create a stable, protective environment for the iron-containing heme groups. This structure allows haemoglobin to bind reversibly with oxygen in the lungs and efficiently release it to the tissues throughout the body.
3. What are the major types and functions of globulin proteins?
Globulins are classified into three main types based on their movement in an electric field (electrophoresis):
Alpha (α) and Beta (β) globulins: These proteins primarily act as transport molecules. They carry substances like lipids, hormones, and metal ions (such as iron in transferrin) through the bloodstream.
Gamma (γ) globulins: These are also known as immunoglobulins or antibodies. Their main function is to provide immunity by identifying and neutralising foreign invaders like bacteria and viruses.
4. How are globulin and immunoglobulin related?
The relationship is one of category and sub-type. Globulin is the broad family of proteins. Immunoglobulin (also known as an antibody) is a specific type of gamma globulin. Therefore, all immunoglobulins are globulins, but not all globulins are immunoglobulins. The other types, like alpha and beta globulins, have different functions unrelated to immunity.
5. If both are globular proteins, why are globin and globulin classified so differently?
While both have a compact, spherical (globular) shape, their classification is based on different criteria. Globin is classified based on its highly specific structure (the 'globin fold') and singular function—binding heme for oxygen transport. It's a functional and structural classification. Globulin, on the other hand, is a broader, older classification based on physical properties, primarily its solubility in saline solutions and its migration pattern in electrophoresis. This category includes hundreds of functionally and structurally diverse proteins.
6. How does the structure of globin facilitate oxygen transport compared to the diverse structures of globulins?
Globin's structure is highly specialised. Its specific tertiary structure, known as the 'globin fold,' creates a protective hydrophobic pocket for the heme group. This pocket prevents the iron in heme from being permanently oxidised, allowing for the crucial reversible binding of oxygen. In contrast, globulins exhibit a vast array of structures tailored to their varied roles. For example, the Y-shape of an immunoglobulin is perfectly designed for its antigen-binding function, which is fundamentally different from oxygen transport.
7. What is the clinical importance of the Albumin-to-Globulin (A/G) ratio in blood tests?
The Albumin-to-Globulin (A/G) ratio is a crucial diagnostic marker used to assess health, particularly liver and kidney function. Since albumin and globulins are the two major protein groups in the blood, their ratio provides important insights. A low A/G ratio might suggest overproduction of globulins (as seen in chronic infections or multiple myeloma) or underproduction of albumin (indicating potential liver disease or kidney issues). A high A/G ratio is less common but could point to genetic disorders or certain leukaemias.
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
