How photosynthesis and respiration feed each other

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

2. 1.

   Ari reads a graph for one leaf at five light levels. At which light level does the CO₂ taken in by photosynthesis equal the CO₂ released by respiration?

   • Light 20
   • Light 30, where photosynthesis is just above respiration
   • Light 40, where photosynthesis is highest
   • Light 0, where the leaf sits in the dark
3. 2.

   Bo uses the same graph. What is the leaf's net CO₂ change at light 40?

   Use the picture in question 1.

   • 8 mL taken in per hour
   • 3 mL taken in per hour
   • 5 mL released per hour
   • 13 mL taken in per hour
4. 3.

   Esme reads the same graph. Which statement does it support?

   Use the picture in question 1.

   • The two lines are unrelated, so where they cross means nothing
   • At light 0 the leaf takes in CO₂ because photosynthesis runs in the dark
   • Below light 20 the leaf gives off more CO₂ than it takes in
   • Above light 20 respiration stops, so photosynthesis takes over

5. Read this first

   Use the table

   Card (model data). Two sealed bottles sit in bright light for 6 hours.

   bottle	contents	CO₂ at the start (ppm)	CO₂ at the end (ppm)
   A	a pond plant	400	250
   B	a pond plant and a cup of yeast in sugar water	400	340

6. 4.

   Kira's class reads about two bottles in bright light (model data). Why did bottle B end with more CO₂ than bottle A?

   • The plant and the yeast did not affect each other, so chance made the gap
   • The plant stopped photosynthesizing because the yeast shaded it
   • Yeast cells released CO₂, which offset some of the plant's uptake
   • The yeast did photosynthesis and made extra CO₂
7. 5.

   Luz reads the card. How many O₂ molecules escaped from the model leaf to the air?

   • 324 molecules
   • 36 molecules
   • 360 molecules
   • 396 molecules

8. Use this

   Flow diagram drawn as a loop (model, not to scale), inside a leaf cell. Two process boxes: photosynthesis, in the chloroplast, on the left; cellular respiration, in the mitochondrion, on the right. An arrow from photosynthesis to cellular respiration carries: glucose; oxygen. An arrow from cellular respiration back to photosynthesis carries: carbon dioxide; water. A wavy arrow points into photosynthesis: light energy. A wavy arrow points out of cellular respiration: energy moved to ATP and heat. Notebook, 3 lines. Line 1: In bright light a leaf takes in more CO₂ than it releases. Line 2: So respiration must switch off whenever light shines on the leaf. Line 3: In the dark, photosynthesis stops and respiration keeps releasing CO₂.

9. 6.

   Noah reads a notebook entry about light and dark. Which line has a flaw?

   • Line 2: mitochondria keep respiring in light while photosynthesis runs faster
   • No line: respiration is a night process
   • Line 3: photosynthesis keeps running in the dark
   • Line 1: a leaf in light takes in oxygen, not CO₂

10. Use this

    Flow diagram drawn as a loop (model, not to scale), inside a leaf cell. Two process boxes: photosynthesis, in the chloroplast, on the left; cellular respiration, in the mitochondrion, on the right. An arrow from photosynthesis to cellular respiration carries: glucose; oxygen. An arrow from cellular respiration back to photosynthesis carries: carbon dioxide; water. A wavy arrow points into photosynthesis: light energy. A wavy arrow points out of cellular respiration: energy moved to ATP and heat. Notebook, 3 lines. Line 1: The carbon atoms in glucose came from CO₂ taken in by the leaf. Line 2: The oxygen gas the leaf releases is the oxygen of that CO₂, set free when the carbon joins glucose. Line 3: In respiration, the carbon atoms of glucose leave the leaf as CO₂.

11. 7.

    Pia reads a notebook entry that traces carbon and oxygen. Which line has a flaw?

    • Line 3: respiration keeps the carbon of glucose inside the leaf
    • Line 2: the released oxygen comes from splitting water, not from CO₂
    • No line: the three lines match the loop
    • Line 1: the carbon in glucose comes from soil minerals

12. Use this

    Flow diagram drawn as a loop (model, not to scale), inside a leaf cell. Two process boxes: photosynthesis, in the chloroplast, on the left; cellular respiration, in the mitochondrion, on the right. An arrow from photosynthesis to cellular respiration carries: glucose; oxygen. An arrow from cellular respiration back to photosynthesis carries: carbon dioxide; water. A wavy arrow points into photosynthesis: light energy. A wavy arrow points out of cellular respiration: energy moved to ATP and heat.

13. 8.

    Ren's friend says the loop is perfect: energy goes around it forever, just like the carbon. Which reply is best?

    • Disagree: matter cycles, but energy enters as light and some leaves as heat
    • Agree: the energy released in respiration powers the next round of photosynthesis
    • Disagree: neither matter nor energy passes between the two processes
    • Agree: heat from respiration is turned back into light and reused
14. 9.

    Tala's friend says plants do only photosynthesis, because breaking glucose down is what animals do. Which reply is best?

    • Disagree: plants respire in their chloroplasts, which do both jobs
    • Disagree: plant mitochondria also break glucose down, using some of the leaf's oxygen
    • Disagree: plants respire, but after dark once photosynthesis stops
    • Agree: plant cells have no mitochondria, so they cannot break glucose down
15. 10.

    Zee's friend says the oxygen a leaf releases is the oxygen of the CO₂ it took in. Which reply is best?

    • Disagree: the light energy turns directly into O₂ gas
    • Disagree: the O₂ comes from glucose that the mitochondria break down
    • Agree: the leaf removes the carbon from CO₂ and releases the oxygen as O₂
    • Disagree: the O₂ comes from splitting water, and the CO₂ carbon goes into glucose