Except blood, the cells of connective tissue secrete certain substances that act as matrix. These substances are

Options

A. Conjugated proteins
B. Signalling molecules
C. Cholesterol
D. Modified polysaccharides

Answer

To answer the question regarding the substances secreted by the cells of connective tissue that act as the matrix (excluding blood), we can break down the information as follows:

### Step-by-Step Solution:

1. **Understanding Connective Tissue**:
- Connective tissue is a type of tissue that supports, binds together, and protects tissues and organs of the body. It consists of cells and an extracellular matrix.

2. **Components of the Matrix**:
- The matrix of connective tissue is primarily composed of various substances secreted by the connective tissue cells. These substances include:
- **Complex Polysaccharides**: These are long chains of sugar molecules that provide structural support.
- **Glycoproteins**: These are proteins that have carbohydrate groups attached to them, playing a crucial role in cell signaling and structural integrity.
- **Fibrous Proteins**: These proteins, such as collagen and elastin, provide strength and elasticity to the tissue.
- **Glycosaminoglycans (GAGs)**: These are a type of complex polysaccharide that helps in retaining water and providing cushioning.

3. **Functions of the Matrix**:
- The matrix serves several important functions:
- It provides density and structural support to the tissue.
- It aids in the mechanical support of other tissues.
- It facilitates the exchange of nutrients and waste products between the blood and surrounding tissues.

4. **Conclusion**:
- Therefore, the substances secreted by the cells of connective tissue that act as the matrix include complex polysaccharides, glycoproteins, fibrous proteins, and glycosaminoglycans.

### Final Answer:
The substances secreted by the cells of connective tissue that act as the matrix are complex polysaccharides, glycoproteins, fibrous proteins, and glycosaminoglycans.

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