Given a scientific passage and an answer, generate a question for the given answer.

[EX Q]: Passage: When electrons are removed from an atom, that process requires energy to pull the electron away from the nucleus. Addition of an electron releases energy from the process. Answer: energy
[EX A]: What is required when electrons are removed from an atom, and released from the process when an electron is added?

[EX Q]: Passage: Membranes Biological membranes surround cells and serve to keep the insides separated from the outsides. They are formed of phospholipid bilayer1 s, which by definition are a double layer of fatty acid2 molecules (mostly phospholipid3 s, lipids containing lots of phosphorus). Proteins4 serve very important functions in cellular membranes. They are active transports in and out of the cell, acting as gatekeepers. They relay signals in and out of the cell. Proteins are the site of many enzymatic reactions in the cell, and play a role in regulation of cellular processes. Answer: biological membranes
[EX A]: What is it that surrounds cells and serve to keep the insides separated from the outsides?

[EX Q]: Passage: Cooling and crystallization. Deep within the Earth, temperatures can get hot enough to create magma. As magma cools, crystals grow, forming an igneous rock. The crystals grow larger if the magma cools slowly, as it does if it remains deep within the Earth. If the magma cools quickly, the crystals will be very small. When crystals form from magma it is called crystallization . Answer: crystallization
[EX A]:
What is it called when crystals form from magma?

