Enzymes
Quick Notes
- Enzymes are proteins that function as biological catalysts.
- They operate under mild temperature and pH.
- Highly specific for substrates.
- Activity influenced by temperature, pH, and substrate concentration.
- Enzymes contain an active site where the substrate binds.
Full Notes
Enzymes are biological catalysts that accelerate the rate of chemical reactions in living organisms. They are highly specific and efficient, playing vital roles in digestion, metabolism, and cellular regulation.
Mechanism of Enzyme Action
Enzymes work by lowering the activation energy required for a reaction to proceed. The mechanism generally follows these steps:
- Substrate Binding: The substrate (reactant) binds to the active site of the enzyme, forming an enzyme–substrate complex.
- Lock and Key Model – substrate fits exactly into the active site.
- Induced Fit Model – enzyme changes shape slightly to fit the substrate.
- Catalysis: The enzyme catalyses the conversion of the substrate into product(s). During this, chemical bonds in the substrate are broken or formed.
- Product Release: The product is released from the enzyme. The enzyme remains unchanged and is reused for another cycle.
E + S ⇌ ES → E + P
(Enzyme + Substrate ⇌ Enzyme–Substrate Complex → Enzyme + Product)
Factors Influencing Enzyme Activity
Temperature:
Optimal activity at specific temperatures (often ~37 °C for human enzymes).
pH:
Each enzyme has an optimum pH range (e.g., pepsin at pH ~2).
Substrate Concentration:
Activity increases with substrate concentration up to a point (saturation).
Inhibitors:
Substances that reduce enzyme activity by blocking the active site or altering the enzyme structure.
Summary
- Enzymes are protein catalysts with specific active sites.
- They follow lock-and-key or induced-fit binding to form ES complexes.
- Activity depends on temperature, pH, and substrate concentration.
- Inhibitors decrease enzyme activity by interfering with binding or structure.