Which of the following statements about enzymes are correct ?
(i) Enzymes do not alter the overall change in free energy for a reaction.
(ii) Enzymes are proteins whose three dimensional energy.
(iii) Enzymes speed up reactions by lowering activation energy.
(iv) Enzymes are highly specific for reactions.
(v) The energy input needed to start a chemical reaction is called activation energy.

Options

A. (i) and (v)
B. (ii) and (iv)
C. (i),(ii) and (iv)
D. All of these

Answer

To determine which statements about enzymes are correct, let's analyze each statement one by one.

**Step 1: Analyze Statement (i)**
- **Statement:** Enzymes do not alter the overall change in free energy for a reaction.
- **Analysis:** This statement is correct. Enzymes lower the activation energy required for a reaction to occur but do not change the overall free energy change (ΔG) of the reaction.

**Step 2: Analyze Statement (ii)**
- **Statement:** Enzymes are proteins whose three-dimensional energy.
- **Analysis:** This statement is incomplete and somewhat misleading. Enzymes are indeed proteins, and their three-dimensional structure is crucial for their function, but the phrase "three-dimensional energy" is not scientifically accurate. Therefore, this statement is not correct.

**Step 3: Analyze Statement (iii)**
- **Statement:** Enzymes speed up reactions by lowering activation energy.
- **Analysis:** This statement is correct. Enzymes act as catalysts and lower the activation energy required for reactions, thus speeding them up.

**Step 4: Analyze Statement (iv)**
- **Statement:** Enzymes are highly specific for reactions.
- **Analysis:** This statement is correct. Enzymes are highly specific and typically catalyze only one type of reaction or act on a specific substrate, similar to a key fitting into a lock.

**Step 5: Analyze Statement (v)**
- **Statement:** The energy input needed to start a chemical reaction is called activation energy.
- **Analysis:** This statement is correct. Activation energy is indeed the energy required to initiate a chemical reaction.

**Final Conclusion:**
Based on the analysis:
- Correct statements: (i), (iii), (iv), and (v).
- Incorrect statement: (ii).

**Final Answer:**
The correct statements about enzymes are (i), (iii), (iv), and (v).

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