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

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
What is it that surrounds cells and serve to keep the insides separated from the outsides?

Passage: Plants in the haploid generation are called gametophytes . They form from haploid spores. They have male and/or female reproductive organs and reproduce sexually. They produce haploid gametes by mitosis. Fertilization of gametes produces diploid zygotes. Zygotes develop into the diploid generation. Answer: through mitosis
How do gametophyte plants form haploid gametes?

Passage: Voltmeters have high resistances and are placed in the circuit in parallel. Answer: in parallel
How are voltmeters placed in the circuit?