Structure And Two Functions Of Proteins

Introduction:

Based on the biochemical structure of the protein, it is macromolecules or large biomolecules that is made up of one or more connected long chains of amino acids residues. A single linear chain consisting of different amino acids is known as polypeptides. One protein molecule is consisting of at least single polypeptide. Protein is associated with different functions ranges from the catalysis of metabolic reaction to DNA replication. Protein is important for human body in term of conducting several cellular functions, such as repairing and maintaining the cell functions, energy production, production of different hormones and enzymes, transportation and storage of different molecules through the blood and formation of antibodies. This assignment is going discuss the overall biochemical structure of protein. Moreover, this study will also discuss the variety of functions of protein which is essential for maintaining the proper physical health.

Protein structure:

Protein is considered as the biological polymer, that consists of amino acids that are linked together by the peptide’s bonds (Clabbers et al. 2017). Through peptides bonds amine acids are connected to each other and form polypeptide chain. One and more poly peptides chains are twisted in a 3D shape in order to for the protein molecule. Protein molecules has different shapes such as curve, loops and twisted form. Folding of the polypeptides chains occurs spontaneously. The chemic bond between the amino acids holds the polypeptides chain strong, which gives the proper shapes and structure to each protein, molecule. There are two different general classes of protein molecules such as

• Fibrous protein
• Globular protein

Globular protein is generally, soluble, compact and spherical in shape. On the hand, the fibrous protein is typically insoluble and elongated (Clark et al. 2016).

Based on the degree of the complexity in the polypeptide chains, protein molecules is classified into four major types:

Primary Structure:

Primary protein structure demonstrates the unique order of the amino acids, in which all the amino acids are connected together to form the protein molecules. Here, the protein molecule consists of 20 amino acids that are connected to each other through peptide bonds.

Generally, the structure of amino acid in each protein molecule is as follows:

• A carbon, the alpha carbon that is connected to the four groups below
• A hydrocarbon (H)
• Carboxyl group (-COOH)
• Amino group (-NH2)
• R group or Variable group (R)

In all amino acids there is one alpha carbon that is chemically bonded to the hydrogen atom, amino group and carboxyl group. The presence of “R” group varies with the different structure of amino acids (Crowe and Bradshaw, 2014). Differences between the protein monomers determines the presence of “R” group in the amino acids. The seconds of amino acids is determined through information of the cellular genetic codes. The order of all the amino acids is unique for the particular type of protein.

Secondary structure:

In the secondary protein structure, the polypeptides are folded and twisted to give the protein a 3D folding shape (Kirk, 2014). Two types of structure can be seen in the secondary structure of protein

• One type is alpha helix structure (α)
• The second type is Beta pleated sheet (β)

In the alpha helix structure (α), the polypeptides chain resembles the coiled spring, that is secured and protected through the hydrogen bond. on the other hand, in the second Beta pleated sheet structure, the shape of the polypeptide chains is like folded and pleated structure, in which the polypeptides are held together through the hydrogen bond between the polypeptide units of folded chain residing adjacent to each other.

Tertiary structure:

It is the comprehensive and complex 3D structure of protein, in which there are different binds as well as forces that holds the protein in proper manner thereby offering the tertiary structure to the protein molecule (Crowe and Bradshaw, 2014).

Hydrophobic interaction:

This interactional is responsible for folding as well as shaping of the polypeptide chains in the tertiary protein structure. The “R” group in the amino acids maty be either hydrophilic or hydrophobic (Kirk, 2014). In case of the amino acids with hydrophilic R group, it seeks the aqueous environment. The amino acids with hydrophobic R group, always avoid the contact with water.

Hydrogen bond:

Hydrogen bond is present between the amino acids “R” group and polypeptide chain, that provides the structural strength and proper shape to the protein molecule

Ionic bond:

During the protein molecule folding process, ionic bond also develops between the negative and positive changed “R” group of amino acids.

Quaternary structure:

This structure is formed through the chemical interaction among the multiple polypeptide chains. This structure is considered as the large protein macromolecules, in which each polypeptide chain is refed as the subunit (Stryer et al. 2019). In case of this type of protein, each protein molecule can consist of more than one similar type of protein subunits. Moreover, the quaternary protein molecules also consist of more than one different type of protein subunits.

Haemoglobin is the example of quaternary protein, that is present in blood. It is the iron containing protein that connects to the oxygen molecule,

Protein functions:

Protein is important source of energy in the human body. It has several important functions. Two of the major functions of protein are as follows:

Protein as the building blocks of body:

Protein acts as the building block of body by taking active and primary part in repairing and maintaining of the body tissues, muscle and organs. According to Stryer et al. (2019), protein is crucial in development and repairing of skin, tissue, eyes, hair and muscle.

The body has ability to produce the amino acids that are important for proper physical construction. There are eight essential amino acids for adults such as leucine, lysine, histidine, isoleucine, methionine, threonine, tryptophan, phenylalanine and Valine. These eight amino acids are essential for assisting the body to perform the repairing and maintaining process.

Storage and transportation of molecule

Protein is one of eth most important transportation molecule in the body, which carry different molecules, gas and particles through the blood into the different cells of the body (Crowe and Bradshaw, 2014). Protein acts as the carrier molecule, transportation molecule that transport the important molecules through the body fluid into the destination organ.

For example, haemoglobin is the transportation protein that carries oxygen and transport this throughout the body. Ferritin acts as the storage protein molecule that attaches to the iron and store the important molecules into the body cells.

Conclusion:

From the above discussion it can be concluded that, protein is the macromolecule or biomolecules that comprises at least one polypeptide chain, each polypeptide chain is formed of several amino acids which are connected to each other through peptide bonds. Protein has four main structure based on the degree of the complexity in the polypeptide chain, such as primary, secondary, tertiary and quaternary structure. Protein is associated with several important functions such as energy source for body, repairing and maintaining activities in the body, tissue formational, enzyme and hormone production and transportation of the molecule.

Reference list:

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