Denaturation of Proteins and Its Causes

Dhristi JEE 2022-24

Denaturation of Proteins

Denaturation can be defined as a process that occurs as proteins folded structure ceases to function. We already know that living organisms might require many types of molecules both small and large in order to survive but what needs all attention is the fact that only a few of them are used as proteins. Let us understand what proteins mean, proteins are large molecules that are composed of folded chains of amino acids which varies in shape, and understanding of the shape is important because that unique shape determines the things it does, we can think of them as keys that fit into certain logs around the body, the same mechanism is used in locating the proteins and its function with respect to the structure it has. Just like other things in the body, proteins have their own set of merits and perform a lot of different things around the body including speeding up biological processes, recognizing antibodies, proteins are the basis of structure to certain body parts, they regulate genes and also help in transporting substances. Proteins may range in various sizes from small to large, an example of a small size protein can be insulin, which has only 51 amino acids and on the other hand, we can take the example of titin, which consists of almost 27 to 28,000 amino acids. Whatever may be the size it is important to know that they must be folded into a particular shape in order to function. It is highly possible that when things go wrong it might cause the protein to unfold and when that happens the process is called denaturation. Denaturation is the process by which proteins lose their folded structure and cease to function.

The Denaturation process occurs as proteins' folded structure ceases to function. Learn the causes behind this occurrence by understanding the four levels of protein structure: Primary, secondary, tertiary, and quaternary. 

What is Denaturation of Protein?

Denaturation of protein is a process that breaks down the strong links or bonds that make up the protein molecules. Protein molecules in their native or natural form have strong bonds and a highly ordered and stable structure. After denaturation of the protein molecule, the links or bonds weaken, and the molecule takes a more loose or random structure, most of them being insoluble. For instance, when food is cooked, like egg or meat, it becomes firm due to the change in the protein molecules after it receives adequate heat. This process can be reversed to regain the original structure. 

If the denaturation agent is removed, the original structure will be restored. This process is called the renaturation of proteins. 

Causes of Denaturation of Proteins 

Many physical and chemical conditions maintain the stability of the protein molecule. If those conditions are disarranged, the molecular structure will change and cause disruption. 

  • Temperature maintains stability to a great extent. The heat can disrupt hydrogen bonds and non-polar hydrophobic interactions. When heat is applied, it causes the molecules to vibrate, and it increases the kinetic energy, which disrupts the molecular structure.

  • Due to certain changes in the pH level, temperature, and chemical structure, the hydrogen bonds are disrupted, which results in the unfolding of globular proteins and uncoiling of the helix structure. Thus, the denaturation of proteins takes place, and the secondary and tertiary structures are destroyed. Heavy salts disrupt the protein molecule structure in the same manner as the salts and the bases.

  • Denaturation breaks the covalent bonds and disrupts the amino acid chains. For instance, alcohol of a very high concentration can disrupt the hydrogen bonding in amide groups in the secondary or tertiary protein structure in various amino acid combinations.

Process of Denaturation of Protein

The process of denaturation of protein is discussed below.

  • Denaturation can easily change the secondary, tertiary, and quaternary protein structure. The primary structure remains intact.

  • Heating, acids, and bases can act as an agent to disrupt the protein molecule bonds due to violent physical reactions.

  • The protein molecule structure can also change by heavy metal poisons that bind the functional group to the protein surface.

  • Any physical change or chemical change can do the process. For example, when the egg is boiled, the heat that acts as an agent disrupts the molecular structure and turns the liquid substance into a semi-solid one. Similarly, in beating the egg, the molecular structure is disrupted due to the change in kinetic energy.  

  • Most of the denaturation process cannot be reversed. However, there is a certain exception in which the process could be reversed, called the renaturation of proteins. For instance, when milk is curdled, it turns into a semi-solid substance called curd due to the molecules' rapid movement and the increase in kinetic energy. However, this entire process cannot be reversed. The curd cannot be converted to milk.  

The Structure of Proteins

  1. Primary Structure

The primary structure can be defined as the basic structure of a protein which has a sequence of amino acids that form that particular protein, as mentioned above every protein has a unique sequence of amino acids that are linked or interlinked in a long chain, these proteins are in a chain together because they perform certain functions bye being together now if the amino acids are out of order the protein will not function properly.

For example, insulin has a chain that begins with the amino acid glycine followed by isoleucine, Valine, and glutamic acid, the change continues as we go further but if anyone particle or protein from the chain goes out of order or is switched with the other than that combination of the chain will not give us insulin because the way a protein is structured, in a unique sense, gives us the product that we required in a sequenced manner so anything out of order will deliver us something inappropriate.

  1. Secondary Structure

Please can be understood by proteins that refer to regular repeated patterns in the folding of amino acid chains. Once the sequencing is done and the chain is formed, the secondary structure identifies patterns in these folds. There are two types of holding that we see at this level which are alpha helixes and beta sheets.

The alpha helix is a spiral coil shape that is said to be formed by hydrogen bonds between amino acids of the same chain. These bones are responsible and cause the chain to go back around in the spiral pattern that we see.

Beta sheets are formed when two chains of amino acid alliance and in turn the assets of these two Chains form hydrogen bonds with one another. With this mechanism it causes them to change to run parallel to each other, which gives us a flatter wrinkled pattern.

Additionally, proteins can be divided into two categories which are fibrous and globular. Fibrous proteins tend to be insoluble in water and globular or more soluble in water. What is an IT structure that we see in the proteins describes the arrangement of subunits that are present in a protein which is made up of more than one subunit. Four major types of attractive interactions determine the shape and stability of the folded protein which are ionic bonding, hydrogen bonding, disulfide linkages, and dispersion forces.

​​An example that we see in a day to day life is when we have a fried egg, we can observe denaturation there as well. The clear egg white turns opaque, this is a result of albumin getting denatured and coagulated. This process has not yet been reversed. The process where a folded protein would unfold is under extensive research and it is highly possible that under sufficiently general conditions it can re-fold and may start showing or exhibiting its natural biological activity.

Extra Facts

  • The duration of denaturation and the temperature required for denaturation vary from sample to sample. 

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FAQs (Frequently Asked Questions)

1. What is the process to turn egg whites from clear to white?

Objects like eggs change colour when exposed to heat or high temperature. The protein structure conforms to the most important component of a living creature. The hydrogen bonding dictates the tertiary structure of the protein molecule. When the egg is exposed to a temperature above 41 degrees Celsius, the protein structure is broken down, and it changes form and colour. In this case, it turns from clear to white. The entire liquid form of the egg, which was the state before the process of denaturation, solidifies. There are many different processes to turn the egg white from clear to white.

2. Name the factors that cause denaturation of proteins?

Various reasons cause the denaturation of protein. Some of them are an increased temperature that ruptures the protein molecules' structure, changes in pH level, adding of heavy metal salts, acids, bases, protonation of amino acid residues, and exposure to UV light and radiation.

3. How is the process of denaturation of proteins important to human beings?

The process of denaturation is extremely important to live beings. When we ingest food, and it goes to our stomach, the acids present over there, that is, HCL breaks down the protein molecule components so that the body can easily consume the nutrition. Without breaking the secondary and tertiary protein structure, facilitate the working ability of pepsin enzymes to convert it into peptides. Thus, digestion would not have been properly possible without the denaturation of proteins.