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

Passage: Hormones Hormones are molecular signals that help regulate a number of biochemical processes. Single amino acids and short protein chains are very common types of hormones. For example, insulin is a protein hormone that regulates the amount of glucose present in the bloodstream. Answer: hormones
What do you call the type of molecular signals that include insulin and that help regulate a number of biochemical processes?

Passage: Centrioles are rod-like structures made of short microtubules. Nine groups of three microtubules make up each centriole. Two perpendicular centrioles make up the centrosome . Centrioles are very important in cellular division, where they arrange the mitotic spindles that pull the chromosome apart during mitosis. Answer: centrioles
What are the rod-like structures made of short microtubules that play an important part in cellular division?

Passage: Caffeine is an example of a psychoactive drug. It is found in coffee and many other products (see Table below ). Caffeine is a central nervous system stimulant . Like other stimulant drugs, it makes you feel more awake and alert. Other psychoactive drugs include alcohol, nicotine, and marijuana. Each has a different effect on the central nervous system. Alcohol, for example, is a depressant . It has the opposite effects of a stimulant like caffeine. Answer: psychoactive drug
What term describes a drug that has an effect on the central nervous system?