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Coffee and Your Brain

High school learnscience.org

Name Date

Predict

Many adults drink coffee in the morning to wake up. Coffee has a chemical in it called caffeine. Does the caffeine in coffee give your body energy?

Circle one. Yes / No

Why?

Watch

  1. Coffee doesn’t give you energyyoutube.com/shorts/qIIaPqW8qkk

Word of the day

Adenosine (uh-DEN-uh-seen). A molecule made of adenine joined to the sugar ribose. In the brain, adenosine builds up during waking and signals the need for sleep.

Word partComes fromMeaning
aden-Greek adḗngland
-os-ribosea sugar found in RNA
-ineFrench and Latin -inaan ending used in the names of chemical substances
  • Your adenoids, at the top of your throat, carry the same aden- root.
  • Caffeine has the same -ine ending. Its name comes from café, the French word for coffee.

Bonus words. Receptor (rih-SEP-tur) is a protein on or in a cell that a molecule binds to, starting a change in the cell. The word comes from Latin and is related to receive. Antagonist (an-TAG-uh-nist) is a molecule that binds a receptor and blocks the receptor’s signal. The word comes from the Greek antagōnízesthai, “to contend against.” In a story, the antagonist is the hero’s opponent.

Questions

  1. Caffeine is an adenosine receptor antagonist. An antagonist binds a receptor and blocks the receptor’s signal without turning the receptor on. Caffeine gives brain cells no energy. Why does blocking adenosine receptors still make a person feel more alert?

    Hint. Think about what adenosine’s signal does in the brain. What happens when less of adenosine’s signal gets through?

  2. Caffeine blocks two kinds of adenosine receptors, A1 and A2A, about equally. In one set of experiments, caffeine still kept mice awake when the mice had no working A1 receptors. Caffeine did not disrupt sleep in mice with no working A2A receptors. Which receptor do the mouse experiments point to for caffeine’s wake-up effect?

    Circle one. A1 / A2A / Both equally

    Hint. Find the mice that slept normally after caffeine. Which receptor were those mice missing?

  3. Caffeine is absorbed in the small intestine and carried by the blood. Caffeine binds adenosine receptors in the brain and in organs such as the heart and blood vessels. In a 1978 study, 250 mg of caffeine raised adrenaline in the blood by 207% and raised blood pressure within an hour. Caffeine goes in your mouth and ends up changing both your brain and your heart. How does caffeine get there? Name the body systems at each step.

    Hint. Trace caffeine from the small intestine to the brain and the heart. Which systems carry the caffeine, and which systems respond?

  4. In rats and mice, daily caffeine increased the number of adenosine receptors in the brain. How could extra adenosine receptors change what a daily coffee drinker feels when the caffeine wears off?

    Hint. Picture the receptors once caffeine leaves. Which molecule is waiting to bind, and how many places can that molecule bind now?

Claim, evidence, reasoning

In rats and cats, adenosine outside brain cells rose during waking, fell during sleep and rose higher after long stretches of waking. When adenosine binds A1 receptors, brain cells release less glutamate, a signal that excites other brain cells. In negative feedback, a change triggers a response that undoes the change. Does adenosine work as a negative feedback signal that keeps sleep and waking in balance? Make a claim, back it up with evidence, and explain your reasoning. Then name one measurement that would test your claim.

Hint. Follow the loop. What does waking do to adenosine, what does adenosine push the brain to do, and what does sleep do to adenosine?

Claim

Evidence

Reasoning

Going further: caffeine and energy

  1. In a 2013 study, adults took 400 mg of caffeine 6 hours before bed. Use a 5-hour half-life. About how much of the 400 mg dose was still in the body at bedtime?

    Circle one. About 50 mg / About 100 mg / About 175 mg / About 400 mg

    Hint. After 5 hours, half of the 400 mg is left. The sixth hour removes a little more.

  2. ATP, short for adenosine triphosphate, carries energy inside cells. Cellular respiration breaks down food and oxygen and forms new compounds that carry energy, such as ATP. Brain cells make adenosine when brain cells use up ATP. Why can’t caffeine give cells energy the way food does?

    Hint. Follow where the energy in ATP comes from. Then think about what caffeine does at the receptor.

Exit ticket

In the video, Raven says coffee is not giving you energy. What does caffeine do in the brain instead? And why does the tired feeling come back later?

Hint. Think about what an antagonist does at a receptor. Then think about the adenosine that keeps forming while caffeine sits in the receptors.

Sources