Why do nitrogen molecules have a bond order of three, whereas oxygen molecules have a bond order of two?

This is because the electron configuration of Nitrogen is 2.5 while that of oxygen is 2.6. This is putting into perspective that the stable configuration for this period of elements is 2.8. Therefore Nitrogen would require 3 electron to reach stable configuration (2.8) while oxygen requires 2. This means that in sharing of electrons in covalent bonds, nitrogen will form three(3) bonds while oxygen will form two (2).

the answer is: the „power stroke“ step.

muscle contraction can be divided into a few steps:

1. the release of ach (acetylcholine) in the synaptic cleft, binding of ach for its receptor and consequently opening of the ca channels.

2. the release of ca, binding of ca for the troponin

3. troponin shifting the tropomyosin, which was blocking the active site on the actin

4. myosin heads attaching to actin by breaking down atp to adp+ pi

5.   formation of the ‘cross-bridge’ on the active site of the actin filament by myosin head

6. “power stroke” -the cross bridge pulls actin, which slides over the myosin

9.     7. the release of adp completes the cross-bridge movement and atp attaches to myosin, breaking the actin-myosin cross bridge.