**Core Concept**
Mucopolysaccharides, also known as glycosaminoglycans (GAGs), are a type of complex carbohydrate that play a crucial role in various physiological processes, including cell growth, differentiation, and tissue structure. They are composed of a core protein with covalently attached carbohydrate chains, which provide them with unique properties and functions.

**Why the Correct Answer is Right**
Mucopolysaccharides are involved in maintaining the integrity and function of connective tissue, cartilage, and other extracellular matrices. They interact with growth factors, cytokines, and other signaling molecules to regulate cell proliferation, migration, and differentiation. The carbohydrate chains of mucopolysaccharides also contribute to their ability to bind water, forming a gel-like substance that provides structural support and tissue hydration.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect, as mucopolysaccharides are not a type of glycoprotein, but rather a distinct class of complex carbohydrates.
**Option B:** Incorrect, as mucopolysaccharides are not solely involved in energy storage, although they do contribute to the storage of water and electrolytes in tissues.
**Option C:** Incorrect, as mucopolysaccharides are not directly involved in the synthesis of nucleic acids, although they do play a role in maintaining the structure and function of cells.

**Clinical Pearl / High-Yield Fact**
Mucopolysaccharidoses, a group of genetic disorders caused by enzyme deficiencies involved in mucopolysaccharide breakdown, can lead to the accumulation of these complex carbohydrates in tissues, resulting in a range of clinical manifestations, including skeletal abnormalities, cognitive impairment, and organ dysfunction.

**Correct Answer:** D.