The curvature of the crista junctions is due to a protein complex called MICOS (mitochondrial contact site and cristae organizing system).

TLS Online TPP Program

#Id: 8371

#Unit 2. Cellular Organization

In the presence of ATP,  myosin head releases from the actin filament. 

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#Id: 8372

#Unit 2. Cellular Organization

Thick-filament regulation

Myosin-dependent mechanism regulate contraction in smooth muscle and non-muscle cells.

TLS Online TPP Program

#Id: 8373

#Unit 2. Cellular Organization

In vertebrate smooth muscle, phosphorylation of the myosin regulatory light chain activates contraction in Ca2+ dependent manner.

TLS Online TPP Program

#Id: 8374

#Unit 2. Cellular Organization

When the Ca2+ levels drop:

Myosin LC is dephosphorylated by MLC phosphatase, causing muscle relaxation.

TLS Online TPP Program

#Id: 8375

#Unit 2. Cellular Organization

Ca2+ dependence of vertebrate skeletal muscle contraction, depends on :

action potential

specialized accessory proteins Tropomyosin,

Troponin (T, I, and C)

TLS Online TPP Program

#Id: 8376

#Unit 2. Cellular Organization

Myosin 

Actin-based motors powered by ATP hydrolysis.