Which of the following is not involved in muscle contraction?

Options

A. A) Creatine phosphokinase
B. B) Troponin
C. C) Calcium ions
D. D) All of the above are involved in muscle contraction

Answer

To determine which of the following is not involved in muscle contraction, we need to analyze each option provided:

1. **Creatine Phosphokinase (CPK)**: This enzyme plays a crucial role in the energy metabolism of muscle cells. It helps regenerate ATP from creatine phosphate, which is essential for muscle contraction. Therefore, CPK is involved in muscle contraction.

2. **Propionyl**: This term refers to a chemical group or compound that is not typically associated with muscle contraction. It does not play a direct role in the muscle contraction process.

3. **Calcium Ions (Ca²⁺)**: Calcium ions are critical for muscle contraction. They bind to the troponin complex on the actin filaments, causing a conformational change that allows myosin to bind to actin, leading to muscle contraction.

4. **All of the Above**: This option suggests that all the previous options are involved in muscle contraction.

Now, evaluating the options, we find that:

- **Option A (Creatine Phosphokinase)**: Involved in muscle contraction.
- **Option B (Propionyl)**: Not involved in muscle contraction.
- **Option C (Calcium Ions)**: Involved in muscle contraction.
- **Option D (All of the Above)**: Incorrect since not all options are involved.

Thus, the correct answer to the question "Which of the following is not involved in muscle contraction?" is **Option B: Propionyl**.

### Step-by-Step Solution:
1. Identify the role of each option in muscle contraction.
2. Analyze the function of Creatine Phosphokinase (CPK) in ATP regeneration.
3. Understand the significance of Calcium ions in the muscle contraction mechanism.
4. Determine that Propionyl does not have a role in muscle contraction.
5. Conclude that the correct answer is Option B: Propionyl.