Activation of the M2 receptors decreases cyclic adenosine 3′,5′-monophosphate (cAMP) in the cells, and this slows the opening of Ca 2+ channels.

TLS Online TPP Program

#Id: 8312

#Unit 2. Cellular Organization

Actin exists as: 

a globular monomer -G-actin 

a filamentous polymer- F-actin

TLS Online TPP Program

#Id: 8313

#Unit 2. Cellular Organization

3 isoforms of actin-

α - expressed only in muscle cells

β and γ - found together in almost all non-muscle cells

TLS Online TPP Program

#Id: 8314

#Unit 2. Cellular Organization

Each actin subunit (globular or G-actin) is a 375-amino-acid polypeptide contains a Mg+2 ion complexed with either ATP or ADP

TLS Online TPP Program

#Id: 8315

#Unit 2. Cellular Organization

Actin can reversibly assemble into filaments that consist of two helices of actin subunits

TLS Online TPP Program

#Id: 8316

#Unit 2. Cellular Organization

Persistence length,

minimum filament length at which random thermal fluctuations are likely to cause it to bend.

TLS Online TPP Program

#Id: 8317

#Unit 2. Cellular Organization

Actin polymerization in vitro proceeds in three steps:

1.Nucleation phase

2.Elongation phase

3.Steady-state