Which type of organism would not have chloroplasts?
a. cacti
b. plants from greenhouse
c. mushrooms
d. photosynthetic protists

Answer and Explanation:

The steps of the sliding filament theory are:

Muscle activation: breakdown of energy (ATP) by myosin.

Before contraction begins, myosin is only associated with a molecule of energy (ATP), which myosin breaks down into its component molecules (ADP + P) causing myosin to change shape.

Muscle contraction: cross-bridge formation

The shape change allows myosin to bind an adjacent actin, creating a cross-bridge.

Recharging: power (pulling) stroke

The cross-bridge formation causes myosin to release ADP+P, change shape, and to pull (slide) actin closer to the center of the myosin molecule.

Relaxaction: cross-bridge detachment

The completion of the pulling stroke further changes the shape of myosin. This allows myosin and ATP to bind, which causes myosin to release actin, destroying the cross-bridge. The cycle is now ready to begin again.

The repeated cycling through these steps generates force (i.e., step 2: cross-bridge formation) and changes in muscle length (i.e., step 3: power stroke), which are necessary to muscle contraction.