**Core Concept**
Mucopolysaccharides, also known as glycosaminoglycans (GAGs), are complex polysaccharides found in connective tissue, composed of a protein core with a long chain of negatively charged sugar molecules. Uronic acid is a key component of many GAGs, particularly hyaluronic acid, chondroitin sulfate, and dermatan sulfate.

**Why the Correct Answer is Right**
The correct answer is **Heparin**. Heparin is a unique GAG that does not contain uronic acid, unlike other GAGs. Instead, it is composed of a repeating disaccharide unit of glucosamine and glucuronic acid isomers are not present in heparin; it is made up of D-glucosamine and L-iduronic acid (iduronic acid) or L-glucuronic acid (glucuronic acid isomers are not present in heparin) along with N-acetyl glucosamine. This distinct composition allows heparin to have anticoagulant properties.

**Why Each Wrong Option is Incorrect**
**Option A:** Hyaluronic acid contains uronic acid, specifically glucuronic acid.
**Option B:** Chondroitin sulfate contains uronic acid, specifically glucuronic acid.
**Option C:** Dermatan sulfate contains uronic acid, specifically iduronic acid.

**Clinical Pearl / High-Yield Fact**
Heparin's unique composition and anticoagulant properties make it a crucial medication in preventing and treating thrombosis, especially in patients undergoing surgical procedures or suffering from deep vein thrombosis.

**Correct Answer:** . Heparin