_____ results from the deposition of uric acid crystals in joints and soft tissues that results in inflammation.

Choice A reason: Actin is a structural protein that forms the thin filaments in muscle fibers. While it interacts with myosin during contraction, it does not bind calcium directly.

Choice B reason: Tropomyosin is a regulatory protein that blocks the myosin-binding sites on actin in a resting muscle. It shifts position when calcium binds to troponin but does not itself bind calcium.

Choice C reason: Titin is a large elastic protein that helps maintain the structural integrity of the sarcomere and contributes to passive elasticity. It does not function as a calcium receptor.

Choice D reason: Troponin is the correct answer. It is a regulatory protein complex associated with the thin filament. When calcium ions bind to troponin, it induces a conformational change that moves tropomyosin away from actin’s binding sites, allowing muscle contraction to occur.

Choice E reason: Dystrophin is a structural protein that connects the cytoskeleton of muscle fibers to the extracellular matrix. It is important for muscle integrity but does not bind calcium.

Choice A reason: Perforating canals (also known as Volkmann's canals) connect the central canals of different osteons and allow blood vessels and nerves to travel across bone. While they contribute to nutrient transport, they do not directly facilitate exchange between osteocytes.

Choice B reason: Lamellae are concentric rings of bone matrix within osteons. They provide structural support but do not directly mediate nutrient or waste exchange between osteocytes.

Choice C reason: Central canals (Haversian canals) contain blood vessels and nerves and run longitudinally through osteons. They help deliver nutrients to the bone but do not directly connect individual osteocytes.

Choice D reason: Canaliculi are microscopic channels that connect osteocytes within lacunae to each other and to the central canal. These channels allow for the direct exchange of nutrients and waste products between osteocytes, making them the most direct structure for this function.