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 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
   • 2 CO2 have left in the matrix, and 4 carbons are in the acetyl groups

3. 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.

4. 2.

   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
   • 6 glucose and 36 O2
   • 3 glucose and 3 O2
   • 3 glucose and 18 O2

5. Use the table

   Breathing rate card (model data). Each breath moves the same amount of air.

   moment	breaths per minute
   resting	15
   during a 3-minute run	36
   after 5 minutes of rest	18

6. 3.

   Bo reads the breathing card (each breath moves the same amount of air). How many times more air is breathed per minute in the run, and where is the extra oxygen used?

   • 21 times as much, used in glycolysis in the cytoplasm
   • 2.4 times as much, used at the electron transport chain
   • 0.4 times as much, used at the electron transport chain
   • 2.4 times as much, used in the lungs for cellular respiration
7. 4.

   In this model cell, chemiosmosis makes exactly 90 percent of the ATP. Esme reads a model cell. Chemiosmosis made 27 ATP from one glucose, exactly 90 percent of all its ATP. How many ATP did the cell make in all?

   • 24, because 27 × 0.9 is about 24
   • 30, because 27 is 90 percent of 30
   • 3, because the other 10 percent is 3
   • 29, because glycolysis adds a net 2 ATP to the 27

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

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

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?

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

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

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

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?

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