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

[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: Analogous structures are structures that are similar in unrelated organisms. The structures are similar because they evolved to do the same job, not because they were inherited from a common ancestor. For example, the wings of bats and birds, shown in Figure below , look similar on the outside. They also have the same function. However, wings evolved independently in the two groups of animals. This is apparent when you compare the pattern of bones inside the wings. Answer: analogous
[EX A]: What term is used to describe structures that are similar in unrelated organisms?

[EX Q]: Passage: Figure 7.14 Maxillary Bone The maxillary bone forms the upper jaw and supports the upper teeth. Each maxilla also forms the lateral floor of each orbit and the majority of the hard palate. Answer: maxillary bone
[EX A]:
What bone forms the upper jaw and supports the upper teeth?