instruction:
Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
question:
Saturated hydrocarbons hydrocarbons contain only single bonds between carbon atoms.
answer:
What hydrocarbons contain only single bonds between carbon atoms?

question:
Chemical digestion mainly occurs in the small intestine.
answer:
Where does chemical digestion mainly occur?

question:
Vesicles are used during endocytosis to allow molecules to enter the cell.
answer:
What cellular structure is used during endocytosis to allow molecules to enter the cell?