Question

Smooth muscle is characterized by all of the following EXCEPT ________. a) it appears to lack troponin b) there are noncontractile intermediate filaments that attach to dense bodies within the cell c) there are no sarcomeres d) there are more thick filaments than thin filaments.

Answer 1

Answer:

There are more thick filaments than thin filaments. (Ans. D)

Explanation:

Smooth muscle doesn't contain the calcium binding protein troponin. In smooth muscle, contraction is initiated by a calcium regulated phosphorylation of myosin, rather than a calcium activated troponin system.

The intermediate filaments are connected to each other with the help of dense bodies, which are attached to adherens junction in the cell membrane of the smooth muscle cells which are known as sarcolemma.

Smooth muscle cell lack sarcomeres because their filaments occur as a spiral and actin, myosin filaments are not regularly arrayed along the length of the cell.

In smooth muscle thin filaments occurs more than thick filaments.

So, the answer is D.