Cellular respiration: the equation and its three stages

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Use this

   Flow diagram (model, not to scale), drawn across a cell. Inputs in boxes on the left: 1 glucose (6 carbons). Outputs in boxes on the right: 2 acetyl groups (2 carbons each); CO2 released. Stage 1, in the cytoplasm: glucose becomes 2 pyruvate (3 carbons each). Stage 2, in the mitochondrial matrix: each pyruvate loses 1 carbon as CO2 and becomes an acetyl group.

2. 1.

   Pia tracks the carbons of 1 glucose through glycolysis and then pyruvate oxidation. How many CO2 have left, and how many carbons are in the acetyl groups?

   • 2 CO2 have left in the matrix, and 6 carbons are in the acetyl groups
   • 2 CO2 have left in the matrix, and 4 carbons are in the acetyl groups
   • 2 CO2 left in the cytoplasm during glycolysis, and 4 carbons are in the acetyl groups
   • 4 CO2 have left in the matrix, and 2 carbons are in the acetyl groups

3. Use this

   Flow diagram (model, not to scale), drawn on the inner mitochondrial membrane. Inputs in boxes on the left: oxygen, O2 (atoms labeled); electrons and hydrogen ions from NADH. Outputs in boxes on the right: water. A wavy arrow points out: energy used to make ATP. Earlier stages release CO2 in the matrix, and they do not use oxygen directly.

4. 2.

   In a model, Ren puts a label on the oxygen atoms in O2 and follows them. According to the last stage of respiration, where do the labeled atoms end up?

   • In the glucose that the cell rebuilds
   • In the water formed at the electron transport chain
   • In the ATP made by ATP synthase
   • In the CO2 released by the citric acid cycle

5. Use this

   Flow diagram (model, not to scale), drawn inside a cell. Inputs in boxes on the left: glucose, amount not shown; oxygen, amount not shown. Outputs in boxes on the right: 18 CO2 released (model data); water.

6. 3.

   A model cell releases 18 CO2 as it breaks down glucose by cellular respiration. Zee uses the equation. How many glucose were broken down, and how many O2 were used?

   • 18 glucose and 18 O2
   • 3 glucose and 3 O2
   • 6 glucose and 36 O2
   • 3 glucose and 18 O2
7. 4.

   Read about only: the teacher handles the equipment. Ari's class adds tube C with 10 g of the same germinating bean seeds, kept in the same conditions. Which prediction fits the card?

   • About 6.0 mL of each gas, because the same kind of seeds respire at the same rate
   • About 12.0 mL of oxygen and 24.0 mL of CO2, since respiration creates extra energy and gas
   • About 12.0 mL of oxygen and 0 mL of CO2, since plant cells use up carbon dioxide
   • About 12.0 mL of oxygen and 12.0 mL of CO2, since twice as many cells respire

8. Notebook lines (model data)

   line	notebook says
   1	Glycolysis happens in the cytoplasm
   2	Pyruvate is oxidized to an acetyl group in the mitochondrial matrix
   3	The citric acid cycle happens in the cytoplasm
   4	The electron transport chain sits in the inner mitochondrial membrane

9. 5.

   Jun's notebook lists four lines about cellular respiration. One line has a flaw. Which line has the flaw?

   • Line 1: glycolysis happens in the mitochondrial matrix, not the cytoplasm
   • Line 3: the citric acid cycle happens in the matrix, not the cytoplasm
   • Line 2: pyruvate is oxidized in the cytoplasm, not the matrix
   • Line 4: the chain sits in the matrix, not the inner membrane

10. Use this

    Notebook line (model data), 1 row. Columns: line, notebook says. 1, Glycolysis nets 4 ATP per glucose, which is most of the ATP a cell makes.

11. 6.

    Kira's notebook says glycolysis nets 4 ATP per glucose, which is most of the ATP a cell makes. What is the flaw?

    • Glycolysis nets 2 ATP, and chemiosmosis makes about 90 percent of the ATP
    • Glycolysis nets 6 ATP, and chemiosmosis makes the rest
    • Glycolysis nets 4 ATP, and the later stages add a few more
    • Glycolysis nets 2 ATP, and the lungs make about 90 percent of the ATP

12. Breathing and muscle card (model data)

    moment	breaths per minute	oxygen used by leg muscle cells (relative units)
    resting	13	1
    after 3 minutes of fast walking	22	3
    after 2 minutes of rest	15	1

13. 7.

    Luz says the card proves breathing is cellular respiration, because both numbers rise together. What is the flaw?

    • Breathing moves air in and out; cellular respiration is the reaction in cells
    • Nothing is wrong, since breathing is how cells make ATP
    • Cellular respiration happens in the lungs, which speed up with breathing
    • The card shows muscle cells created extra energy, not respiration
14. 8.

    “Flow diagram (model, not to scale)” Milo says leaf cells make their own glucose, so they do not need cellular respiration. Which reply is correct?

    • Disagree: plant mitochondria break sugars down with oxygen to make ATP
    • Agree: plant cells make food, so they skip the breakdown of glucose
    • Disagree: leaves breathe through tiny openings, and that breathing is their cellular respiration
    • Agree: plants use light for their ATP, so mitochondria are not needed
15. 9.

    Flow diagram (model, not to scale), drawn across a cell. Noah says cellular respiration creates the energy a cell uses. Which reply is correct?

    • Disagree: the energy comes from the oxygen turning into CO2
    • Agree: the cell creates the energy, which is why glucose gets used up
    • Disagree: glycolysis moves the energy into ATP, and the later stages add little
    • Disagree: it moves energy that glucose already stored into ATP and heat

16. Use this

    Notebook page with a flow diagram (model, not to scale), drawn across a cell. Inputs in boxes on the left: 6 O2, which holds 12 oxygen atoms. Outputs in boxes on the right: 6 CO2, which holds 12 oxygen atoms. Last stage, on the inner mitochondrial membrane: oxygen accepts electrons and forms water.

17. 10.

    Tala counts 12 oxygen atoms in 6 O2 and 12 in 6 CO2, and says the oxygen a cell takes in becomes its CO2. Which reply is correct?

    • Disagree: oxygen forms water at the last stage, and the CO2 carbon comes from glucose
    • Agree: the counts match, so the O2 oxygen moves into the CO2
    • Disagree: the CO2 is released by glycolysis in the cytoplasm
    • Disagree: the oxygen is used in the lungs, so cells make CO2 without it