Fibrous vs Globular Proteins
Proteins are biological compounds that are composed of one or more polypeptide chains. Each polypeptide chain is made up of amino acids bound together by peptide bonds. Thus, the functional and structural unit of protein is amino acid. Due to their huge molecular mass, proteins are considered as one of the most important macromolecules in the body. During the synthesis of proteins, polypeptide chains are folded up to form specific three-dimensional (3D) structures. Depending on the nature of these three- dimensional structures proteins are divided into two main categories; namely, globular and fibrous proteins. These two types of proteins are equally important as they carry out many functions in the body.
What is Globular Protein?
Globular proteins are water soluble proteins with spherical shapes and irregular amino acid sequences. The polypeptide chains are folded in, to form their shapes, and this shape is specific for each globular protein type. The water solubility of globular proteins enables them to transport through blood and other body fluids to various locations where their action is required.
Globular proteins mainly involve in carrying many chemical reactions, which enable organisms to convert outside energy sources to usable energy form. These proteins also act as catalysis for thousands of chemical reactions occurring in the body. Moreover, globulin proteins involve in glucose metabolism, oxygen storage in muscles, oxygen transport in blood, immune responses etc. Some examples for globular proteins are insulin, myoglobin, hemoglobin, transferrin, and immunoglobulins.
What is Fibrous Protein?
Fibrous proteins are water insoluble proteins that form various types of structures such as rigid, rod-like, sheet-like etc. As the name implies, most of the fibrous proteins are extensively cross-linked to form fibrous structures.
Fibrous proteins mainly involve in supporting functions such as providing tensile strength, elasticity, rigidity, and structural functions such as forming membrane structures, scaffold structures inside cells etc. Fibrous proteins can be found in skin, hair, nuclear membrane, red blood cell membranes etc. Some examples for fibrous proteins are F-actin, collagen, desmin, elastin, fibroin, keratin etc.
What is the difference between Globular Protein and Fibrous Protein?
• Globular proteins are water soluble, whereas fibrous proteins are generally water insoluble.
• Fibrous proteins involve in structural functions such as providing support and protection while globular proteins are responsible for certain metabolic functions such as catalysis, transport, and regulation.
• Globular proteins often have several types of secondary structure, whereas fibrous proteins contain a single type of secondary structure.
• The number of different types of globular proteins is higher than that of fibrous proteins.
• Being the most abundant protein in the human body, fibrous proteins have a higher total mass than globular proteins.
• Examples for fibrous proteins are keratin and collagen, whereas examples for globular proteins are hemoglobin and myoglobin.
• Globular proteins have much more weaker secondary and tertiary bonds than in fibrous proteins thus globular proteins denature easily than fibrous proteins.