**Core Concept**
Collagen is the most abundant protein in the human body, comprising approximately 25% to 35% of all proteins. It is a type of structural protein that provides strength and elasticity to tissues, particularly in the skin, bones, tendons, and ligaments.

**Why the Correct Answer is Right**
Collagen is primarily composed of three polypeptide chains, also known as alpha helices, which twist together to form a triple-helix structure. This unique structure provides the strength and elasticity necessary to maintain the integrity of the skin. Type I collagen is the most abundant type of collagen in the skin, comprising approximately 90% of collagen found in the dermis. It is produced by fibroblasts and plays a crucial role in wound healing.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because collagen is not primarily composed of keratin, which is a type of structural protein found in hair, nails, and skin but is not the main component of collagen.
**Option B:** This option is incorrect because elastin is a type of protein that provides elasticity to tissues but is not a component of collagen.
**Option C:** This option is incorrect because glycoproteins are molecules that contain both carbohydrate and protein components but are not the primary component of collagen.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that collagen is a crucial component of the skin's structure, and its degradation is associated with various skin disorders, including acne, psoriasis, and scleroderma.

**Correct Answer: A. Type I collagen is the primary type of collagen found in the skin.**