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TLS Online TPP Program

#Id: 8256

The negative sign indicates that energy is released out of the system, because energy is released when bonds are formed, even weak bonds.

#Unit 1. Molecules and their Interaction Relevant to Biology #Stablizing interactions (Van der Waals, electrostatic, hydrogen bonding, hydrophobic interaction) #Part B Pointers
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TLS Online TPP Program

#Id: 8406

#Unit 2. Cellular Organization

Vertebrate skeletal muscle contraction, also depends on set of specialized accessory proteins that are closely associated with the actin thin filaments:

a) Tropomyosin

b) Troponin
TLS Online TPP Program

#Id: 8408

#Unit 2. Cellular Organization

Tropomyosin (TM) is a ropelike molecule, about 40 nm in length, binds to 7 actin subunits in an actin filament.
TLS Online TPP Program

#Id: 8409

#Unit 2. Cellular Organization

Troponin, a complex of three polypeptides, 
TN-T (tropomyosin-binding)
TN-I  (inhibitory)
TN-C (Ca2+-binding)
TLS Online TPP Program

#Id: 8410

#Unit 2. Cellular Organization

TN-C is the calcium-binding subunit, controls the
position of TM on the surface of an actin filament through the TN-I and TN-T subunits
TLS Online TPP Program

#Id: 8411

#Unit 2. Cellular Organization

In the absence of Ca2+, muscle is relaxed
TM blocks myosin’s interaction with F-actin
TLS Online TPP Program

#Id: 8412

#Unit 2. Cellular Organization

Binding of Ca2+ ions to TN-C
triggers movement of TM to a new position on the filament, thereby exposing the myosin-binding sites on actin.