Which one of the followign pairs of substances and function is not correctly matched?

Options

A. actin : slides past myosin causing contraction
B. Calcium : Triggers enzymatic action of Myosin
C. ATPase : Enzyme that splits ATP
D. ATP : Supplies energy for breaking Actomyosin

Answer

To determine which pair of substances and functions is not correctly matched, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Identify the first pair: Actin and Myosin**
- **Function**: Actin slides past myosin causing contraction.
- **Explanation**: This is based on the sliding filament theory proposed by A.F. Huxley and H.E. Huxley in 1954. According to this theory, actin filaments slide over myosin filaments during muscle contraction. This statement is correctly matched.

2. **Identify the second pair: Calcium and Myosin**
- **Function**: Calcium triggers enzymatic action of myosin.
- **Explanation**: In a resting state, the binding site for myosin on actin is covered by the troponin-tropomyosin complex. When calcium ions bind to troponin, it causes a conformational change that uncovers the binding site for myosin. However, the statement claims that calcium triggers the enzymatic action of myosin, which is incorrect. Calcium does not directly trigger myosin's enzymatic action; rather, it facilitates the exposure of the binding site on actin. Therefore, this statement is not correctly matched.

3. **Identify the third pair: ATPase and ATP**
- **Function**: ATPase is an enzyme that splits ATP.
- **Explanation**: ATPase activity on the myosin head breaks down ATP into ADP and phosphate. This statement is correctly matched.

4. **Identify the fourth pair: ATP and Actomyosin**
- **Function**: ATP supplies energy for breaking actomyosin.
- **Explanation**: The release of ADP and phosphate allows a new ATP molecule to bind to the myosin head, leading to the dissociation of the myosin head from the actin filament. This statement is also correctly matched.

### Conclusion:
The pair that is not correctly matched is the second one: **Calcium triggers enzymatic action of myosin**.

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