The smallest and most abundant serum proteins are

Options

A. Albumins
B. Globulins
C. Clotting factors
D. Immunoglobulins

Answer

To answer the question "The smallest and most abundant serum proteins are," we will analyze the options provided and determine which one fits the criteria of being both the smallest and most abundant serum protein.

### Step-by-Step Solution:

1. **Understanding Serum**:
- Serum is the liquid portion of blood that remains after the blood has clotted. It is essentially blood minus the clotting factors.

2. **Analyzing the Options**:
- **Option A: Albumin**
- Albumins are proteins that are known for their role in maintaining osmotic pressure in the blood. They are indeed the most abundant proteins found in serum.
- **Option B: Globulins**
- Globulins are a group of proteins that play various roles, including immune functions, but they are not the most abundant serum proteins.
- **Option C: Clotting Factors**
- Clotting factors are proteins involved in the blood coagulation process. However, they are not present in serum since serum is defined as blood without these factors.
- **Option D: Immunoglobulins**
- Immunoglobulins are antibodies that are part of the immune response. While they are important, they are not the most abundant serum proteins.

3. **Conclusion**:
- After evaluating the options, we find that albumins are the smallest and most abundant serum proteins. Therefore, the correct answer is **Option A: Albumin**.

### Final Answer:
The smallest and most abundant serum proteins are **Albumin**.