Fibrous and Globular Proteins
Protein is present abundantly in our body. They are compounds formed by amino acids. These amino acids are attached to one another in a long chain-like structure to form a protein. Proteins are polymers or macromolecules made up of smaller structural units. Most functions in our body occur due to the presence of protein. Different types of protein help in the smooth functioning of our body.
Processes like DNA replication, transporting molecules, providing structural balance to cells and organs, response to stimuli, and metabolic reactions are supported by proteins. Proteins are classified on the basis of the sequence of amino acids, and upon the basis of structure and function. The four different levels of a protein structure are- primary, secondary, tertiary, and quaternary structure. On the basis of function, proteins can be classified as fibrous protein, globular protein, and membrane protein. We will discuss the difference between fibrous and globular proteins and the different types of protein.
Types of Proteins
Protein is present in our hairs, nails, muscles, and in the haemoglobin present in our red blood cells. Depending upon the functions of protein we differentiate protein into three types- globular, fibrous, and membrane proteins. These proteins help in the normal functioning of the body. Let us discuss these three types of proteins in detail.
Globular Proteins:
Globular proteins have a spherical structure. These are one of the most abundant types of proteins. Globular proteins help in bodily functions. These proteins are mostly soluble in water and form colloids. They act as enzymes, messengers, transporters, regulators, and sometimes also as structural protein. Haemoglobin is a common globular protein.
Fibrous Proteins:
Fibrous proteins are made up of sheet-like filamentous structures. Fibrous proteins have low solubility in water. These types of protein provide protection and function in the structural role by forming connective tissues, tendons, and muscle fibres. Fibrous proteins are made up of regular amino acid sequences. The most common form of fibrous protein is collagen.
Membrane Proteins:
Membrane proteins as the name suggests are commonly found and are present in the membranes. They interact with biological membranes and therefore are the target of medicinal drugs. These help in providing receptor signals between the internal and external environments of the cell. Also, they help in transporting molecules and allow interaction between molecules. Types of membrane proteins include integral membrane protein and peripheral membrane protein.
Common Proteins and Their Uses
Globular Proteins
Haemoglobin: It is the red colour pigment found in our red blood cells. Haemoglobin is the reason why our blood is red in colour. Its main function is to store and transport oxygen to different parts of the body. The level of haemoglobin should always be maintained in a body as lower amounts of haemoglobin can lead to lower amounts of oxygen and higher amounts of haemoglobin can lead to thickening of the blood which can further lead to heart attack, strokes.
Insulin: Insulin is formed in our pancreas which regulates the level of sugar in our body. It allows glucose to enter our body so that the cells can provide energy.
Fibrous Proteins
Collagen- It is a type of protein that is most abundant in humans (30%). It is made up of amino acids which are further made up of carbon, hydrogen, and oxygen. It gives strength to our various body parts and also protects them. It is a major part of human skin and nails.
Keratin- It is a type of fibrous protein which is present in our hair, nails, and skin. It can also be found in most of the organs inside our body.
What is the Difference between Fibrous Protein and Globular Protein?
Globular protein and fibrous protein are different types of protein that are essential in the proper functioning of a human body. While globular helps in a variety of functions, fibrous proteins are involved in providing structural stability to the organism. Proteins are made up of amino acid strands.
Globular protein and fibrous protein have some differences. These are due to changes in the structure of the protein and the sequence of amino acids. The differences between fibrous protein and globular protein are given below:
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FAQs on Difference Between Globular and Fibrous Protein
1. Explain the different functions of globular proteins.
Globular proteins are functional proteins that are involved in a variety of bodily functions. Globular proteins are made up of irregularly arranged amino acid sequences. Globular proteins are soluble in water and form corresponding colloids. Other types of protein, fibrous, and membrane are insoluble in water.
Globular proteins are commonly found proteins that are spherical or round. This shape is influenced by the tertiary structure of the protein. Globular proteins have a variety of roles:
Globular proteins act as enzymes and catalyze various organic reactions taking place inside the organism specifically targeting the reaction under mild conditions.
Hormones such as insulin act as messengers of information about biological processes.
Globular proteins help in regulating different biological processes taking place inside the body.
They also act as transporters of molecules through membranes.
Globular proteins also work as structural proteins. These are soluble in water but form long and stiff polymers.
2. Explain the differences in the structures of the protein.
The three-dimensional structure of the protein is essential to its function. The variety of functions that take place in a body is possible due to the presence of protein. These varying properties of proteins are a function of their different structures-
Primary Structure - The amino acid sequence present in the protein defines its primary structure. The unique function of the protein is due to this sequence of amino acids bonded together by peptide bonds.
Secondary Structure - The secondary structure forms an irregular substructure of the protein. Two common arrangements are- alpha helix which adopts a spiral shape and beta-sheet which is made up of side by side arranged amino acids.
Tertiary Structure - The overall three-dimensional structure of the protein is defined by the tertiary structure. Intermolecular forces exist to provide stability between these molecules.
Quaternary Structure - It defines the specific interaction and orientation of the protein structure.
3. What are the major types of interactions which determine the shape of the tertiary structures of the protein?
There are four major types of interactions that take place to form different shapes of the tertiary structure of the proteins. They are given below-
1. Ionic Bonding - As you know, the chains of amino acids have two sides, one is positively charged and the other one is negatively charged. When the two charged ends attract, an ionic bond is formed.
2. Hydrogen Bonding - When a highly electronegative oxygen atom (or a nitrogen atom) and a hydrogen atom attached to another oxygen atom or a nitrogen atom exist, then hydrogen bonding takes place. This can be found in polar amino acid side chains. Both intramolecular interactions and inter-molecular interactions require hydrogen bonding to take place.
3. Disulfide Linkages - This bond or linkage happens between the sulphur-containing side chains of cysteines. This type of bond is much stronger than the rest of the bonds and has a strong stabilising effect.
4. Dispersion Forces - These forces are weak intermolecular forces. Such types of forces arise when in a nonpolar molecule, an instantaneous dipole moment happens because of the uneven distribution of the atoms.
4. Explain the types of membrane proteins.
Membrane proteins mainly present in the membranes help in providing signals between the internal and external environments of the cell. They also help to transport molecules and allow interaction between molecules. The two common types of membrane proteins are integral membrane protein and peripheral membrane protein.
Integral Membrane Protein - This is the permanent part of the plasma membrane. They act as receptors as they receive information and also act as transporters as they help in the movement of the molecules. Examples are insulin receptors, rhodopsin, etc.
Peripheral Membrane Protein - This is the temporary part of the plasma membrane. Their function is to transport materials within or outside the cell. They help to activate proteins and enzymes and also take part in the cell to cell interactions.
