Reading the Gut by Its Gas: teacher key

Burps and Farts, grade 11 edition, written for 11th grade. People pass far more gas in a day than their gut holds at any moment. Breath tests, diet studies and a study that collected every passage of gas from 16 people show where gut gas comes from and where some of it goes.

Read the book. Print this page for the key.

Questions and answers

1. What is the puzzle in the gas numbers?
   • The gut holds under 200 milliliters at a time yet people pass 600 to 700 a day (answer)
   • Gas has no source at all
   • People pass more gas than they eat food
2. What does a rise in breath hydrogen after a test sugar show?
   • Human cells made the hydrogen
   • Gut bacteria have been fermenting the sugar (answer)
   • The person swallowed air
3. Why can methanogens shrink the total volume of gas?
   • They turn several gas molecules into one (answer)
   • They make the gas smell stronger
   • They stop bacteria from living
4. A person's gas is rich in carbon dioxide, hydrogen and methane but low in nitrogen. What does that most likely point to?
   • Swallowed air
   • Bacteria working on food (answer)
   • A carbonated drink only
5. In this passage, what does a gas chromatograph do?
   • It counts how many times a person passes gas
   • It makes gas smell stronger
   • It sorts a gas mix into its parts and measures each (answer)

Words

• aerophagia: swallowing air
• methanogens: methane-making microbes
• microbiome: gut microbe community
• chromatograph: gas-sorting machine
• FODMAPs: fast-fermenting carbohydrates