Which of the following is not a component of saliva?

Options

A. Electrolytes `Na^(+),K^(+),Cl^(-) and HCO_(3)^(-)` ions
B. Ptyalin / `alpha`- salivary amylase
C. Mucin, lysozyme and thiocyanate ions
D. Antibody (IgG)

Answer

To determine which of the following is not a component of saliva, we will analyze the components typically found in saliva and compare them with the provided options.

### Step-by-Step Solution:

1. **Understanding Saliva Composition**: Saliva is a fluid produced by the salivary glands in the mouth. It plays a crucial role in the digestion of food and helps in the formation of food boluses.

2. **Identifying Common Components**: The main components of saliva include:
- **Electrolytes**: Such as sodium (Na+), potassium (K+), chloride (Cl-), and bicarbonate (HCO3-).
- **Enzymes**: The enzyme ptyalin (also known as alpha-salivary amylase) is present, which helps in the digestion of carbohydrates.
- **Mucin**: A glycoprotein that helps in lubricating food.
- **Lysozyme**: An enzyme that has antibacterial properties.
- **Thiocyanate ions**: These also have antibacterial effects.

3. **Reviewing the Options**: Now, we need to look at the options provided in the question and identify which one is not typically found in saliva.

4. **Analyzing Each Option**:
- **Electrolytes**: Present in saliva.
- **Ptyalin (alpha-salivary amylase)**: Present in saliva.
- **Mucin**: Present in saliva.
- **Antibodies**: Generally, antibodies (like IgG) are not found in saliva.

5. **Conclusion**: Based on the analysis, the component that is not found in saliva is **antibodies**.

### Final Answer:
The correct answer is **option 4: antibodies**.