In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.

[EX Q]: Question: Calcium ion is an example of what kind of messenger? Answer: second
[EX A]: Calcium ion is an example of a second messenger.

[EX Q]: Question: A binary molecular compound is made up of two of what? Answer: elements
[EX A]: A binary molecular compound is made up of two elements.

[EX Q]: Question: What is the energy needed to start a reaction between catalysts and reactants called? Answer: activation energy
[EX A]:
Activation energy is the energy needed to start a reaction between catalysts and reactants called.