Which of the following processes require the presence of 02 in order to occur?
a. glycolysis
b. glycogenesis
c. fermentation
d. citric acid cycle
e. more than one is correct

d. Citric acid cycle

Explanation:

The only process in the list that requires the presence of O2 in order to occur is the Citric acid cycle or Krebs cycle. This cycle is part of the aerobic cellular respiration and it occurs only when O2 is available. If there is no oxygen, an alternative process that could happen is fermentation, but this is only carried by some microorganisms and some cells such as muscle cells.  

In fact, oxygen is not needed by citric acid cycle but it is by the next step: the electron transport chain. In this chain, oxygen is the final acceptor of electrons, and without oxygen, the Krebs cycle doesn't occur because the final electron transport chain can't be done.

after a the power stroke, adp is released, but the cross-bridge formed is still in place. atp then binds to myosin, moving the myosin to its high-energy state, releasing the myosin head from the actin active site.