Which of the following activities occurs in both prokaryotic cells and eukaryotic cells? A. Proteins are assembled on ribosomes.
B. A large central vacuole stores DNA and RNA.
C. Mitochondria provide energy for cell processes.
D. Chloroplasts capture and transform the energy of sunlight.
E. The rough endoplasmic reticulum releases enzymes to break apart wastes.

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.