Metabolic Diversity: Choosing an Electron Donor and Acceptor · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.
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Who breathes what, and who wins

Science · Microbiology · ages 19-20
Name ______________________   Date ____________

  1. What is the correct payoff order of final catchers?

    • Sulfate, then nitrate, then oxygen
    • Carbon dioxide, then oxygen, then nitrate
    • Oxygen, then nitrate, then sulfate

  2. What three traits classify a microbe metabolism?

    • Carbon source, energy source, final catcher
    • Size, shape, colour
    • Speed, noise, smell

  3. Where oxygen reaches, oxygen breathers outgrow the alternatives.

    Circle one:   True   False

  4. Who dominates the deepest oxygen free mud layer?

    • Sulfate breathers and methane makers
    • Oxygen breathers
    • Nitrate breathers

  5. A microbe feeds on ready made food, burns chemicals, and ends with nitrate. What is it?

    • Light eater using carbon dioxide with oxygen
    • Chemical eater using organics with nitrate
    • Chemical eater using organics with oxygen

  6. What does electron flow do with the gap energy?

    • It wastes the gap as heat
    • It stores nothing at all
    • It pumps a gradient that mints ATP

  7. A friend says fermentation beats full breathing for yield. Is that right?

    • No, most fuel energy stays locked in its waste
    • Yes, it banks the full gap
    • Yes, gradients play no role

  8. Oxygen vanishes from a bay but nitrate stays. Who takes over?

    • Oxygen users keep winning
    • Nitrate users take the lead
    • All growth stops forever
LightMySky · lightmysky.comW1-mt__2yCr9OSIn-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

Who breathes what, and who wins W1-mt__2yCr9OSIn-s1

  1. Oxygen, then nitrate, then sulfate · Willingness to catch electrons runs oxygen first and carbon dioxide last.
  2. Carbon source, energy source, final catcher · Where carbon and energy come from plus the final catcher fully classifies the lifestyle.
  3. True · The biggest donor catcher gap banks the most ATP per fuel molecule.
  4. Sulfate breathers and methane makers · Deep layers keep only the weakest catchers, so the weak catcher users rule there.
  5. Chemical eater using organics with nitrate · Organics for carbon plus chemicals for energy plus nitrate at the end fits that pattern.
  6. It pumps a gradient that mints ATP · Electron flow pumps a gradient and its return through the synthase mints energy.
  7. No, most fuel energy stays locked in its waste · No outside catcher means electrons fall back inside and the payoff stays tiny.
  8. Nitrate users take the lead · With oxygen gone the next best catcher still available sets the winner.
Worksheet · LightMySky