How photosynthesis and respiration feed each other

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Use the table

   Card (model data). One leaf sits in a sealed jar; the jar is measured in bright light and again in darkness.

   condition	net CO₂ change in the jar (mL per hour)
   bright light	12 taken in
   darkness	4 released

2. 1.

   Ari reads a card for one leaf in a sealed jar. What is the leaf doing in the darkness row?

   • Respiring, which releases CO₂
   • Starting to respire now that the light is off
   • Photosynthesizing, which takes in CO₂
   • Resting, with no gas exchange without light
3. 2.

   Bo sees that the jar lost 12 mL of CO₂ each hour in the bright light row. Which statement fits?

   • Photosynthesis released 12 mL of CO₂
   • The two processes cancelled, leaving no change
   • Respiration stopped, so no CO₂ was released
   • Photosynthesis took in more CO₂ than respiration released
4. 3.

   Assume respiration releases CO₂ at the same rate in bright light as in darkness. Esme uses the card and the stated assumption. How much CO₂ did photosynthesis take in during the bright-light hour?

   • 4 mL
   • 8 mL
   • 16 mL
   • 12 mL

5. Use the table

   Card (model data). One leaf sits in a sealed jar; carbon atoms are counted in the CO₂ gas and in the glucose.

   stage	carbon atoms in CO₂ gas	carbon atoms in glucose
   start	600	0
   after light	480	120
   after darkness	540	60

6. 4.

   Kira counts carbon atoms in a jar with one leaf. How many carbon atoms moved from glucose back into CO₂ gas in the dark?

   • 0 atoms
   • 540 atoms
   • 120 atoms
   • 60 atoms

7. 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.

8. 5.

   Milo compares matter and energy in the loop. Which statement is right?

   • Energy goes round the loop, but matter is used up
   • Matter goes round the loop; energy enters as light and some leaves as heat
   • Neither passes between the boxes; each process works alone
   • Matter and energy both go round the loop again and again
9. 6.

   Noah says the heat from respiration could be collected to power photosynthesis. What energy does photosynthesis use?

   • Heat collected from respiration
   • Glucose the leaf made the day before
   • Oxygen gas carried in from the air
   • Light absorbed by chlorophyll

10. Card for one model leaf (model data)

    step	energy (units)
    light energy absorbed	100
    stored in glucose	40
    released as heat	60

11. 7.

    Pia reads an energy card for one model leaf. Which statement does the card support?

    • The leaf made 60 new units of heat energy
    • The 40 units stored and the 60 units of heat add up to the 100 that came in
    • The glucose holds the full 100 units, since light becomes sugar
    • The 60 units of heat can be gathered to rebuild the 100
12. 8.

    Ren reads that it is noon with bright light. Which processes are running in a leaf cell?

    • Cellular respiration, since photosynthesis needs darkness
    • Both photosynthesis and cellular respiration
    • Neither, since the cell rests at midday
    • Photosynthesis, since respiration waits for dark
13. 9.

    Tala reads that it is midnight and a leaf in a greenhouse gets no light. Which gas exchange fits the leaf?

    • Takes in and gives off nothing without light
    • Takes in O₂ and gives off CO₂
    • Gives off O₂ as it uses up the glucose
    • Takes in CO₂ and gives off O₂

14. Use the table

    Card (real data, from OpenStax Biology 2e). Where the oxygen made in a leaf goes.

    where it goes	share of the oxygen
    used by mitochondria in the leaf	about 10 percent
    escapes to the air	the remainder

15. 10.

    Zee reads the oxygen card. Which statement follows from it?

    • About 10 percent leaves, since mitochondria claim most of it
    • About 90 percent of the oxygen leaves the leaf
    • The whole amount escapes, since plant cells use no oxygen
    • The leaf's mitochondria take no oxygen from it