A mucopolysaccharide that functions as cell cement and lubricant is

Options

A. Heparin
B. Hyaluronic acid
C. Keratan sulphate
D. Chondrotin sulphate.

Answer

To answer the question "A mucopolysaccharide that functions as cell cement and lubricant is," we need to analyze the given options and identify the correct one.

### Step-by-Step Solution:

1. **Understanding Mucopolysaccharides**: Mucopolysaccharides, also known as glycosaminoglycans, are long chains of disaccharide units that play various roles in the body, including structural and lubricating functions.

2. **Evaluating the Options**:
- **Heparin**: Heparin is an acidic glycosaminoglycan produced by basophils and mast cells. Its primary function is as an anticoagulant, preventing blood clotting. It does not act as a cell cement or lubricant. **(Incorrect)**

- **Hyaluronic Acid**: Hyaluronic acid is a mucopolysaccharide composed of glucuronic acid and acetyl glucosamine. It is found in the extracellular fluid, vitreous humor of the eye, and cerebrospinal fluid. Its functions include maintaining the elasto-viscosity of liquid connective tissues, acting as a lubricant by binding water, and serving as a cementing material between animal cells. **(Correct)**

- **Keratin Sulfate**: Keratin sulfate is a type of glycosaminoglycan found in the cornea, cartilage, and bone. It plays a role in corneal development but does not function as a cell cement or lubricant. **(Incorrect)**

- **Chondroitin Sulfate**: Chondroitin sulfate is a major component of cartilage and is used for treating arthritis. While it is important for cartilage structure, it does not serve as a cell cement or lubricant. **(Incorrect)**

3. **Conclusion**: After evaluating all the options, the mucopolysaccharide that functions as cell cement and lubricant is **Hyaluronic Acid**.

### Final Answer:
**Hyaluronic Acid**