Question

During contraction of muscles $C{a}^{2+}$ attaches to

• A. Troponin-C
• B. Troponin-A
• C. Calmodulin
• D. Cal bindin

Answer 1

The correct option is A Troponin-C

• Active sites for myosin are present on actin which are masked by troponin-C in resting state. when Ca++ level increases it leads to the binding of calcium with a subunit of troponin i.e Troponin-C on actin(thin) filaments and thereby remove the masking of active sites for myosin.
  
• Utilizing the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge.
• This pulls the attached actin filaments towards the centre of ‘A’ band.
  
• The ‘Z’ line attached to these actins are also pulled inwards thereby causing a shortening of the sarcomere, i.e., contraction. The myosin, releasing the ADP and P1 goes back to its relaxed state.
• Hence During contraction of muscles Ca ++ attaches to Troponin -C.
• So, the correct answer is 'Troponin-C'