MCQ Detailed View

Enzymes are biological molecules that function as organic catalysts, meaning they accelerate the rate of chemical reactions in living organisms without being consumed in the process. Almost all enzymes are proteins, specifically globular proteins, which have unique three-dimensional shapes that allow them to interact with specific substrates.

The catalytic activity of enzymes comes from their active site, a specialized region on the protein where substrates bind. This site lowers the activation energy required for a chemical reaction, allowing it to proceed much faster than it would without the enzyme. For example, digestive enzymes such as amylase (breaks down starch into sugars), lipase (breaks down fats), and protease (breaks down proteins) are all protein-based catalysts essential for human survival.

Although proteins are the main structural component of enzymes, certain enzymes also require cofactors (inorganic ions such as Mg²⁺, Fe²⁺, Zn²⁺) or coenzymes (organic molecules such as vitamins) to function properly. These help stabilize the enzyme or participate directly in the catalytic process.

While most enzymes are proteins, there are exceptions. Some RNA molecules, known as ribozymes, also possess catalytic activity. However, these are relatively rare compared to the vast majority of protein-based enzymes.

Enzymes play a role in nearly every biological process including:

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  Digestion of food into absorbable nutrients.

  
  


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  DNA replication and repair.

  
  


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  Energy production through metabolic pathways like glycolysis and the Krebs cycle.

  
  


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  Detoxification of harmful substances in the liver.

  
  

Without enzymes, biochemical reactions would be too slow to sustain life. For instance, a reaction that might take years in a test tube can occur in milliseconds with the help of an enzyme.

✅ Key Facts Recap

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  Enzymes = mostly proteins

  
  


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  Function = lower activation energy, speed up reactions

  
  


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  Require cofactors/coenzymes in some cases

  
  


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  Ribozymes exist but are exceptions

  
  


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  Essential in metabolism, digestion, and genetic processes

  
  

👉 Correct Answer: Proteins