Type of Protein and Its Functions

Difference Between Globular and Fibrous Protein

We often notice so many bodybuilders and several physical trainers drinking whey protein along with milk for building up their metabolism and strength. However, when it comes to our body, our hair and nails are made of proteins mostly. Basically, proteins are the fundamental building blocks of the human body. They are large and complex macromolecules, also called bio-molecules that perform a huge role in the functioning and regulating of the body cells, tissues and several other organs in our body. They are also used to provide strength to our body for producing hormones, enzymes, and many other metabolic chemicals. They are also involved in the functioning and the regulation of all our body cells, tissues and organs. Proteins are composed of amino acids that are arranged into several different groups. These fundamental amino acids sequences are known to be specific and all its arrangements are controlled by the human DNA. Since our body is not able to synthesize these essential amino acids by its own, it is essential for us to have plenty of protein foods in our daily diet to keep the metabolisms of our body stable. We will learn about the simple definition of protein, type of protein and its function, the difference between globular and fibrous protein, and the classes of proteins in detail in this article.


Classes of Proteins

The classification of proteins is done on the basis of their shape, constitution and the nature of their molecules. Hence, the different classes of proteins are as follows:


1. On the Basis of Their Shape

  1. Fibrous Protein or Scleroprotein: You can find these kinds of proteins in the animals and they are insoluble in water. Fibrous proteins are resistant to the proteolytic enzymes and are coiled. They tend to exist in threadlike structures and form fibres, for example, collagen, keratin in hair, claws, and feathers, actin, and myosin, etc.

  2. Globular Proteins: Globular proteins, unlike the fibrous proteins are soluble in water. They are made of polypeptides which are coiled around themselves and form oval or spherical molecules like albumin, and insulin, and hormones like oxytocin, etc.

2. On the Basis of Their Constitution

  1. Simple Proteins: Simple proteins are made of just amino acids for example globulins, albumins, prolamins, etc.

  2. Conjugated Proteins: Conjugated proteins are the complex proteins which are combined with the characteristics of the non–amino acid substance known as the prosthetic group.

They are of Following Types:

  • Nucleoproteins: They are a combination of the proteins and the nucleic acid

  • Mucoproteins: They are a combination of the proteins and carbohydrates (>4%)

  • Glycoproteins: They are a combination of proteins and carbohydrates (<4%)

  • Chromoproteins: They are a combination of the proteins and different coloured pigments.

  • Lipoproteins: They are a combination of the proteins and lipids.

  • Metalloprotein: They are a combination of the proteins and metal ions.

  • Phosphoprotein: They are the combination of the proteins and a phosphate group.

  • Derived Proteins: When the proteins are hydrolyzed either by acids, alkalies or enzymes, the degradation products that are obtained from them are known as the derived proteins.

3. On the Basis of the Nature of the Molecules

  1. Acidic Proteins: These exist as the anion and contain acidic amino acids, for example, the blood groups.

  2. Basic Proteins: These exist as the cations and are rich in the basic amino acids, for example, lysine, arginine etc.


Functions of Proteins

The role of protein in the human body is as follows:

Structural Functions: Proteins are called the building blocks of our body. They make for an essential component of several structures in the cells and the tissues. You can also find these proteins in the outer membrane of all the cells that are present in the human body. You can also find the structural proteins in your hair, skin, and muscles. Proteins generally act to strengthen all these structures. Proteins working together would allow movement within the body, for example, the contraction of muscles and the movement of food through your digestive system, etc. These proteins are required for the growth, development, repair and healing of the tissues.

  1. Protective: Proteins are the essential constituent of the antibodies which protect our body from the antigens and pathogens and help to prevent several infections.

  2. Hormonal Regulation: Hormones are usually composed of different proteins. Hormones play a crucial role in the regulation of muscle mass, sex hormones, and the overall growth and development.

  3. Enzymes: Proteins are referred to as biological buffers since they, as enzymes, help to regulate several different biochemical reactions which are occurring in the body.


Structure of Proteins

Since there are different rearrangements of amino acids, the structure of the proteins is divided into four different types:

  1. Primary: The covalent bonds of the proteins

  2. Secondary: The linear peptide chains tend to fold either into an alpha-helical structure which is coiled or a beta-pleated structure which is in the form of sheets that contain hydrogen bonds.

  3. Tertiary: The arrangement and the interconnection of proteins into particular loops and bends form the tertiary structures of the proteins. This structure consists of the hydrogen, ionic and the disulfide bonds.

  4. Quaternary: This structure is proteins that contain more than one peptide chain.

FAQ (Frequently Asked Questions)

1. What are the Two Types of Proteins Found in the Human Body?

There are 20 different amino acids in the proteins which make up each molecule of protein, and these amino acids are therefore split into 2 categories named non-essential amino acids and essential amino acids. Therefore, the two types of protein in the body are non-essential amino acids and essential amino acids. 

  1. Non - Essential Amino Acids: They are produced naturally by the human body

  2. Essential Amino Acids: They are not produced naturally by the human body and hence must be consumed in the food or through supplements

2. Which Type of Protein is Haemoglobin?

Haemoglobin is a kind of conjugated protein. It contains a basic protein called globin which is joined to a non-protein group heme, therefore, the name haemoglobin. The haemoglobin molecule is a complex of 4 different heme molecules that are joined with 4 globin molecules. The name haemoglobin is derived from the two words heme and globin, which reflects the fact that each of the subunits of haemoglobin is a globular protein having an embedded heme group. Each of the heme group consists of one iron atom, which can bind to one oxygen molecule with the help of the ion-induced dipole forces. Hence, haemoglobin is a type of protein called globin.