instruction:
Given a scientific question, generate a correct answer to it.
question:
The major component of what cellular structures is the phospholipid bilayer?
answer:
cell membranes

question:
What is the basic structure that holds plants upright, allowing plants to get the sunlight and air they need?
answer:
stem

question:
When a wave travels down a string, the string vibrates up and down at right angles to the wave's what?
answer:
direction