Stomata are bordered by guard cells, which can open or close the stomata. The guard cells typically close the stomata when the plant has lost excessive water, as light levels in the environment decrease, or when the plant has an excess of carbon dioxide. The guard cells
can open the stomata when carbon dioxide levels in the leaf cells become too low.
The regulation of gas exchange by the guard cells of stomata is an example of

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.

z is the answer.

(sorry caplock) lol

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