The four core histones are present in equal amounts in the cell. H1 is half as abundant as the other histones, which is consistent with the finding that only one molecule of H1 can associate with a nucleosome.

TLS Online TPP Program

#Id: 1413

#Unit 4. Cell Communication and Cell Signaling

When the Ca2+ level rises, Ca2+ binds CaM.

TLS Online TPP Program

#Id: 1414

#Unit 4. Cell Communication and Cell Signaling

The CaM*-Ca2+ complex binds and activates MLC kinase, phosphorylates the myosin LC. 

TLS Online TPP Program

#Id: 1415

#Unit 4. Cell Communication and Cell Signaling

The CaM*-Ca2+ complex binds and activates MLC kinase, phosphorylates the myosin LC. 

TLS Online TPP Program

#Id: 1416

#Unit 4. Cell Communication and Cell Signaling

Phosphorylation of MLC  unfolds the myosin II, active and can assemble into bipolar filaments for contraction. 

TLS Online TPP Program

#Id: 1417

#Unit 4. Cell Communication and Cell Signaling

When the Ca2+ levels drop: Myosin LC is dephosphorylated by MLC phosphatase, causing muscle relaxation.

TLS Online TPP Program

#Id: 1418

#Unit 4. Cell Communication and Cell Signaling

Integrins are the principal receptors used by animal cells to bind to the extracellular matrix.