A) titin B) actin C) elastin D) myosin

Did you know that titin is often referred to as the "Giants of proteins"? This colossal protein plays a crucial role in muscle elasticity and is the largest known protein, with a length of about 1.2 micrometers! It helps keep muscles functioning properly by acting like a spring, which is essential for the contraction and relaxation of muscle fibers. When it comes to real-world applications, actin and myosin are key players in muscle contraction. These proteins work together in a beautiful synchronized dance, converting chemical energy into mechanical work—think of it like the ultimate teamwork in the gym! Their roles extend beyond just muscles; they’re also vital in cell movement, shape, and division, making them essential for life itself!