Question

Read the following statements about enzymes. Which among them are correct?
I. The mechanism by which enzymes work is known as lock and key.
II. They denature at high temperatures.
III. They are mostly proteins having a tertiary structure.
IV. They may be assisted by vitamins and minerals.

• A. I, II and III only
• B. I, II, III and IV
• C. II and IV only
• D. I, II and IV only

Answer 1

Answer: (B)

Enzymes are a group of biomolecules which act as bio-catalyst, speeding up the reaction. These are made up of proteins. When such proteins encounter high temperature, it causes certain bonds to break in the structure, resulting in conformational change (denaturation). This denaturation makes the enzyme inactive and useless as catalyst. For an enzyme to be active, it may need support of non-protein constituents called cofactors, which bind to it, thus, making it catalytically active. These can be organic compounds, vitamins or mineral ions. The working of an enzyme binding to a single substrate was explained using a lock and key analogy given by Emil Fischer. In this analogy, the lock is the enzyme and the key is the substrate; on binding of substrate, the enzyme unlocks and changes the substrate to product. Also, this model explains the specificity of an enzyme as there is only one type of key to open the lock.