Final answer:
The most abundant structural protein in the human body, present in ligaments and skin, is collagen (option 1). It has a triple helix structure and is key in the composition of connective tissues such as tendons and cartilage, making up 25% to 35% of vertebrate proteins.
Step-by-step explanation:
The most abundant structural protein in the human body, found in ligaments and skin, is collagen. Collagen is special because of its triple helix configuration, making it incredibly strong and elastic. This protein is a major component of the extracellular matrix (ECM) and constitutes about 25% to 35% of the protein content in vertebrates. It is found in connective tissues, such as tendons, cartilage, blood vessels, skin, and bone. Collagen fibres provide structural support, serving as the main building block for cells, tissues, and organs. These fibres are fibrous connective tissue that serves as packing and binding material for most of our organs.
Different proteins have various functions based on their structure. For instance, keratin is found in hair and the outer layers of skin, while elastin is principal in ligaments and the elastic tissue of artery walls due to its property of returning to its original shape after being stretched. Knowing the role of these proteins helps in understanding their importance in the human body.