Join thousands of students who trust us to help them ace their exams!Watch the first video
Multiple Choice
At rest, the tropomyosin molecule is held in place by which of the following proteins?
A
Actin
B
Troponin
C
Titin
D
Myosin
Verified step by step guidance
1
Understand the structure of the sarcomere, the functional unit of muscle contraction, which includes actin (thin filaments) and myosin (thick filaments). Tropomyosin is a regulatory protein associated with actin filaments.
Learn the role of tropomyosin in muscle contraction. Tropomyosin blocks the binding sites on actin filaments, preventing myosin heads from attaching to actin and initiating contraction.
Identify the protein responsible for holding tropomyosin in place. Troponin is a complex of three subunits (Troponin T, Troponin I, and Troponin C) that binds to tropomyosin and actin, stabilizing tropomyosin's position on the actin filament.
Understand the interaction between troponin and calcium ions during muscle contraction. When calcium ions bind to Troponin C, it causes a conformational change in the troponin-tropomyosin complex, exposing the binding sites on actin for myosin.
Review the incorrect options: Actin is the filament tropomyosin is associated with, but it does not hold tropomyosin in place. Titin is a structural protein that stabilizes myosin and maintains sarcomere elasticity. Myosin is the motor protein responsible for contraction but does not interact directly with tropomyosin to hold it in place.