**Core Concept**
Collagen is the most abundant protein in the human body, making up approximately 25% to 35% of all proteins. It is a type of structural protein that provides strength and elasticity to connective tissue, which is found in skin, bones, tendons, and ligaments. The triple helix structure of collagen is a unique feature that allows it to provide these structural properties.

**Why the Correct Answer is Right**
The triple helix structure of collagen is formed by three alpha helices that are twisted together, forming a rope-like structure. This structure is stabilized by hydrogen bonds between the amino acid residues of the three helices. The most common amino acid found in collagen is glycine, which is essential for the formation of the triple helix structure. The triple helix structure of collagen allows it to provide strength and elasticity to connective tissue, making it essential for maintaining tissue integrity.

**Why Each Wrong Option is Incorrect**
**Option A:** Cystine is a type of amino acid that is found in some proteins, but it is not associated with the triple helix structure.
**Option C:** Pectin is a type of polysaccharide that is found in the cell walls of plants, but it does not have a triple helix structure.
**Option D:** DNA is a type of nucleic acid that is found in the nucleus of cells, and it has a double helix structure, not a triple helix structure.

**Clinical Pearl / High-Yield Fact**
Collagen is essential for maintaining skin integrity, and defects in collagen can lead to conditions such as osteogenesis imperfecta, which is characterized by brittle bones and skin fragility.

**✓ Correct Answer: B. Collagen**