Mark the correct statement for enzymes.

Options

A. Enzymes in a living system are highly unspecific w.r.t. substrate
B. Enzymes remain unaltered upto the end of chemical reaction
C. All enzymes are thermostable
D. Enzymes increase the activation energy of reactants hence speed up the reaction

Explanation

To determine the correct statement about enzymes, let's analyze each of the provided statements step by step:

1. **Statement 1: Enzymes in the living system are highly unspecific with respect to substrate.**
- Enzymes are known for their specificity. They typically catalyze reactions for specific substrates due to their unique active sites that fit particular substrate shapes. Therefore, this statement is **incorrect**.

2. **Statement 2: Enzymes remain unaltered up to the end of a chemical reaction.**
- Enzymes act as catalysts in biochemical reactions, meaning they facilitate the reaction without being consumed or permanently altered in the process. They return to their original state after the reaction is complete. Hence, this statement is **correct**.

3. **Statement 3: All enzymes are thermostable.**
- Thermostability refers to the ability of an enzyme to remain functional at high temperatures. Most enzymes are not thermostable; they can denature (lose their functional shape) at elevated temperatures. Only a few enzymes, like Taq polymerase, are known to withstand high temperatures. Therefore, this statement is **incorrect**.

4. **Statement 4: Enzyme increases the activation energy of reactants, hence speed up the reaction.**
- Enzymes actually lower the activation energy required for a reaction to occur, which speeds up the reaction. Thus, this statement is also **incorrect**.

After analyzing all the statements, the correct answer is **Statement 2: Enzymes remain unaltered up to the end of a chemical reaction.**