Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fiber?

A. Tropomyosin shifts and unblocks the cross-bridge binding sites.

B. Calcium is released and binds to the troponin complex.

C. Transverse tubules depolarize the sarcoplasmic reticulum.

D. The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP.

E. An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane.

#Question id: 4175

#Unit 3. Fundamental Processes

The initiation codon __.

#Question id: 2582

#Unit 2. Cellular Organization

Following statements are regarding to dynamics of actin filaments.

A. When the concentration of G-actin is above the Cc, the filament end will grow; when it is less than the Cc, the filament will shrink.

B. ATP–G-actin is added much faster at the (+) end than at the (−) end, resulting in a lower critical concentration at the (+) end than at the (−) end.

C. At steady state, actin subunits treadmill through a filament. ATP-actin is added at the (+) end, ATP is then hydrolyzed to ADP and Pi, Pi is lost, and ADP-actin dissociates from the (−) end.

D. ATP–G-actin is added much faster at the (-) end than at the (+) end, resulting in a lower critical concentration at the (-) end than at the (+) end.

E. At steady state, actin subunits treadmill through a filament. ATP-actin is added at the (-) end, ATP is then hydrolyzed to ADP and Pi, Pi is lost, and ADP-actin dissociates from the (+) end.

Which of the following statements are correct?

#Question id: 657

#Unit 1. Molecules and their Interaction Relevant to Biology

Structural proteins that typically assemble into large cables or threads to provide mechanical support to cells or organisms are classified as ________ proteins.

#Question id: 32510

#Unit 1. Molecules and their Interaction Relevant to Biology

#Question id: 11496

#Unit 7. System Physiology – Animal

Forced rapid breathing results in alkalization of the blood which would lead to which of the following changes in neuronal activity?