The enzymes that join together two molecules by forming new covaient bonds are:

Options

A. A) oxidoreductases
B. B) transferases
C. C) lyases
D. D) ligases

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the type of enzyme that joins two molecules by forming new covalent bonds.

2. **Analyzing the Options**:
- **Option A: Oxido-reductases** - These enzymes are involved in oxidation-reduction reactions, not in forming covalent bonds between molecules.
- **Option B: Transferases** - These enzymes transfer functional groups from one molecule to another but do not necessarily form new covalent bonds.
- **Option C: Ligase** - Ligases are enzymes that join two molecules together by forming new covalent bonds, specifically phosphodiester bonds in the case of DNA.
- **Option D: Ligase** - This is a repetition of Option C.

3. **Identifying the Correct Answer**: Based on the analysis, the correct answer is **Ligase** (Option C and D refer to the same enzyme).

4. **Explanation of Ligase Function**: Ligases catalyze the joining of two molecules by forming covalent bonds. For example, DNA ligase joins DNA fragments by creating phosphodiester bonds, which are covalent in nature.

5. **Conclusion**: The enzyme that joins together two molecules by forming new covalent bonds is **Ligase**.

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