B cells migrate to the lymphoid follicles. They are directed there by chemokine interactions between CXCL13, which is secreted by follicular dendritic cells (FDCs).

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#Section 3: Genetics, Cellular and Molecular Biology

Sarcomere

Within each skeletal muscle cell are many myofibrils consisting of a repeating array of a specialized structure

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#Id: 8394

#Section 3: Genetics, Cellular and Molecular Biology

When the Ca2+ levels drop:

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

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#Section 3: Genetics, Cellular and Molecular Biology

Phosphorylation of MLC 

unfolds the myosin II, active and can assemble into bipolar filaments for contraction

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#Section 3: Genetics, Cellular and Molecular Biology

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

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#Section 3: Genetics, Cellular and Molecular Biology

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

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#Id: 8373

#Section 3: Genetics, Cellular and Molecular Biology

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