Describe three dimensional structure of enzyme.

HN Series

  • The enzymes are globular proteins.
  • The specificity of enzymes comes from their unique three dimensional structures.
  • Tertiary structure of a protein or any other macromolecule, play important role in the proper functioning.
  • The simple protein consists of only one long polypeptide chain e.g. ribonuclease consists of amino acids.
  • The kind of amino acids and the sequence in which they are arranged determines the three dimensional structure of an enzyme.

Explain (Catalytic) Characteristics of Enzymes.

Enzymes being catalysts show following characteristics.
Efficiency: They are very efficient in function e.g. one enzyme may catalyze 100,000 substance in one second. (The unit is called as one turnover number).
ii) Specific Temperature: Enzymes need Specific temperature for their proper functioning. drinking cold water during meal is medically wrong.
iii) Specific pH: Enzymes need Specific pH for their proper functioning.
iv) Specific in Action: Enzymes are highly Specific i.e. one enzyme acts only a specific substance
e.g'amylase acts only on amylose.
v. Constant nature: Enzymes remain constant after the reaction so they can be used again and again.
vi. In vivo and in vitro Study: Enzyme may be studied in living cell (in vivo) or outside living
i.e in glassware (in vitro).
vii. Cofactor: Most of enzymes need cofactor for their functioning.
viii. Most of enzymes need co-factor for their functioning.
ix. Medium: Enzymes need aqueous (watery) environment for their functioning, that's why feel thirst after taking meal.
x) Sites: Many enzymes have two sites i.e. allosteric site and active site.


What are Enzyme Cofactors?

Enzyme cofactors are non-protein chemical compounds or metallic ions that are required for an enzyme's biological activity. Think of them as tiny "helper molecules" that an enzyme needs to do its job. An enzyme without its cofactor is called an apoenzyme (inactive), while the complete, active enzyme with its cofactor is called a holoenzyme. 

Types of Cofactors

There are two main types of enzyme cofactors:

1.  Inorganic Ions: These are simple, non-carbon-based ions, such as metal ions. They help the enzyme function by either stabilizing its structure or directly participating in the chemical reaction.

Examples: Zinc (Zn2+), Iron (Fe2+ or Fe3+), Magnesium (Mg2+), and Copper (Cu2+


2.  Coenzymes: These are complex, non-protein organic molecules. Many coenzymes are derived from vitamins and are essential for carrying chemical groups, atoms, or electrons between different enzymes.Examples:

  • Vitamins: Vitamin B1 (Thiamine), Vitamin B2 (Riboflavin), and Vitamin B3 (Niacin).

    • Molecules: ATP, NAD$^+$ (a crucial electron carrier), and FAD.


3. Prosthetic Groups: This is a special type of coenzyme that is very tightly and permanently bound to the enzyme, often through a strong covalent bond. They are an essential and inseparable part of the enzyme's structure.

  • Examples: Heme (found in enzymes like catalase) and Biotin.



Differentiate between metal ions, coenzymes and prosthetic groups.




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