What is the Difference Between Intracellular and Extracellular Enzymes

The main difference intracellular and extracellular enzymes is that intracellular enzymes of endoenzymes function within the cell, aiding intracellular digestion, whereas extracellular enzymes or exoenzymes function outside the cell, aiding extracellular digestion. Furthermore, intracellular enzymes account for the majority of enzymes, while the minority is extracellular enzymes. In addition to these, intracellular enzymes break down large polymers into smaller chains of monomers while extracellular enzymes act on the end of the polymer to break down its monomers one at a time. 

Intracellular and extracellular enzymes are the two types of digestive enzymes present in a cell. Generally, they are categorized based on the location of the action.

Key Areas Covered 

1. What are Intracellular Enzymes
     – Definition, Mechanism of Action, Importance
2. What are Extracellular Enzymes
     – Definition, Mechanism of Action, Importance
3. What are the Similarities Between Intracellular and Extracellular Enzymes
     – Outline of Common Features
4. What is the Difference Between Intracellular and Extracellular Enzymes
     – Comparison of Key Differences

Key Terms 

Digestive Enzymes, Extracellular Enzymes, Intracellular Enzymes, Location of Action

What are Intracellular Enzymes 

Intracellular enzymes or endoenzymes are a type of enzymes functioning inside the cell. They are responsible for undergoing millions of metabolic reactions inside the cell of both eukaryotes as well as prokaryotes. Thus, intracellular enzymes carry out both photosynthesis and cellular respiration inside the cell. Moreover, these enzymes are responsible for carrying out DNA replication, protein synthesis etc. Intracellular enzymes are also responsible for the digestion of food inside food vacuoles in unicellular organisms. This process is known as intracellular digestion. Generally, lysosomes contain these intracellular enzymes. Furthermore, the digestive enzymes in lysosomes are responsible for the cell death of old cells.

Figure 1: Intracellular Enzymes

Furthermore, intracellular enzymes break down large polymers into smaller chains of monomers. For example, the enzyme endoamylasebreaks down large amylose molecules into dextrin chains, which are shorter. In contrast, exoenzymes break down monomer subunits of large polymers, starting from the ends.  

What are Extracellular Enzymes 

Extracellular enzymes or exoenzymes are the enzymes which act outside the cell. Generally, the number of extracellular enzymes is less than the number of intracellular enzymes. Moreover, they are responsible for extracellular digestion, which occurs in the alimentary canal of animals. Here, different types of accessory organs secrete digestive enzymes into the lumen of the alimentary canal through which the food passes. By mixing with these enzymes, carbohydrates, proteins, lipids, and nucleic acids in the food are digested into their monomer units known as monosaccharides and disaccharides, amino acids, fatty acids, and nucleotides, respectively. 

Figure 2: Extracellular Enzymes

Moreover, extracellular enzymes secreted by decomposers to the outside environment are responsible for the digestion of decaying organic matter. Furthermore, decomposers play a key role in ecosystems, recycling nutrients. In addition, these organisms can absorb nutrients, which are the products of the extracellular digestion through their cell wall. Other organisms such as plants can also absorb these nutrients from their roots.  

Similarities Between Intracellular and Extracellular Enzymes  

• Intracellular and extracellular enzymes are the two types of digestive enzymes that occur in cells.  
• Both occur in eukaryotes as well as prokaryotes.  
• They differ by their location of the action.  
• Based on their action, they have different important functions in the cell.  
• However,  their main function is to undergo digestion of food particles.    
• Both are protein molecules made up of chains of amino acids. 

Difference Between Intracellular and Extracellular Enzymes 

Definition 

Intracellular enzymes refer to the enzymes which act inside the cell while extracellular enzymes refer to the enzymes made by the cell but, work in the outside of the cell. 

Also Known as 

Intracellular enzymes are also known as endoenzymes while extracellular enzymes are known as exoenzymes. 

Proportions 

Moreover, intracellular enzymes account for the majority of enzymes while the minority is extracellular enzymes. 

Mechanism of Action 

While itracellular enzymes breakdown large polymers into smaller chains of monomers, extracellular enzymes act on the end of the polymer to breakdown its monomers one at a time. 

Type of Digestion 

Furthermore, intracellular enzymes undergo intracellular digestion while extracellular enzymes undergo extracellular digestion. 

Occurrence 

Intracellular enzymes are responsible for the digestion of food particles inside the cytoplasm of unicellular organisms while extracellular enzymes are responsible for the digestion of food inside the alimentary canal of higher animals and the extracellular digestion in decomposers such as fungi and bacteria. 

Conclusion 

Intracellular enzymes are the enzymes that function inside the cell. Most enzymes are intracellular enzymes, breaking down large polymers into small chains of monomers. Generally, intracellular enzymes occur in unicellular organisms that undergo intracellular digestion of food particles. On the other hand, extracellular enzymes are the minor group of enzymes, functioning outside the cell. In contrast, they breakdown large polymers into monomers starting from the ends. Basically, extracellular enzymes are responsible for the digestion inside the alimentary canal in higher animals as well as the extracellular digestion in decomposers including fungi and bacteria. Therefore, the main difference between intracellular and extracellular enzymes is the location of action and importance. 

References:

1. Intracellular and Extracellular Enzymes, Available Here

Image Courtesy:

1. “Figure 04 04 04” By CNX OpenStax (CC BY 4.0) via Commons Wikimedia   
2. “Organelles of the Secretory Pathway” By Artwork by Holly Fischer – Cell Biology Slide 11; Histology of Glands Slide 4 (CC BY 3.0) via Commons Wikimedia