College of Massage Therapists of British Columbia (CMTBC) Practice Exam

What is the primary role of the muscle protein Titin?

1. Facilitates muscle contraction

2. Stores energy in muscles

3. Provides structure and elasticity

4. Transports calcium ions

The correct answer is: Provides structure and elasticity

The primary role of the muscle protein Titin is to provide structure and elasticity. Titin is one of the largest proteins in the human body and plays a critical role in muscle function. It spans half a sarcomere, connecting the Z-disc to the M-line, which helps to preserve the structural integrity of the sarcomere during muscle contraction and relaxation. Titin's elasticity allows it to stretch and recoil, contributing to the overall passive elasticity of muscle tissue. This is fundamental for maintaining muscle tone, allowing muscles to return to their resting length after being stretched. The elastic properties of Titin also help absorb the force generated during rapid muscle movements, protecting the muscle fibers from damage. In contrast, while muscle contraction is facilitated by other proteins such as actin and myosin, Titin itself does not play a direct role in the active process of contraction. Although muscles do require energy, that function is typically associated with other elements like creatine phosphate and ATP. Furthermore, the transport of calcium ions is carried out by proteins such as the sarcoplasmic reticulum, rather than Titin. Thus, the choice that highlights Titin's role in providing structure and elasticity accurately reflects its primary function in muscle physiology.