9th grade Cellular respiration: the equation and its three stages worksheet

Cellular respiration: the equation and its three stages

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Equation card, from OpenStax Biology 2e

   C6H12O6 + 6O2 → 6CO2 + 6H2O + energy. Inputs in boxes on the left: glucose, C6H12O6; oxygen, 6O2. Outputs in boxes on the right: carbon dioxide, 6CO2; water, 6H2O. A wavy arrow points out: energy.

2. 1.

   Tala counts the oxygen atoms on each side of C6H12O6 + 6O2 → 6CO2 + 6H2O. How many are on the left side, and how many on the right side?

   • 18 on the left and 18 on the right
   • 12 on the left and 18 on the right
   • 12 on the left and 12 on the right
   • 18 on the left and 12 on the right
3. 2.

   Zee counts atoms in the respiration equation and finds both sides balanced. The right side also lists energy. What does the energy term show?

   • New energy that the cell creates during the reaction
   • Energy stored in the CO2 and water, kept for later
   • Energy moved out of glucose's bonds into ATP and heat
   • A product made of atoms that must also be counted
4. 3.

   Ari reads that a potato plant's cells break down 2 glucose in the dark. Using the equation, how many H2O form, and how many hydrogen atoms do they hold?

   • 0 H2O, since plant cells do not break glucose down
   • 6 H2O holding 12 hydrogen atoms
   • 12 H2O holding 12 hydrogen atoms
   • 12 H2O holding 24 hydrogen atoms

5. Use this

   Flow diagram (model, not to scale), drawn inside a mitochondrion. Inputs in boxes on the left: pyruvate (3 carbons). Outputs in boxes on the right: acetyl CoA (2 carbons); CO2 (1 carbon); NADH. No wavy arrow label is drawn.

6. 4.

   Bo reads a model where pyruvate loses one carbon as CO2 while NADH forms. Which stage is this, and where does it happen?

   • Pyruvate oxidation, in the mitochondrial matrix
   • Pyruvate oxidation, in the cytoplasm
   • Glycolysis, in the mitochondrial matrix
   • Electron transport chain, on the inner membrane

7. Use this

   Flow diagram (model, not to scale), drawn inside a mitochondrion. Inputs in boxes on the left: NADH in the matrix; oxygen at the inner membrane. Outputs in boxes on the right: CO2 leaving the matrix; water forming at the inner membrane. No wavy arrow label is drawn.

8. 5.

   Jun reads a diagram with CO2 leaving the matrix and water forming at the inner membrane. Which stage uses oxygen directly?

   • The lungs, which use the oxygen as soon as it is breathed in
   • Glycolysis, which starts by splitting glucose in the cytoplasm
   • The citric acid cycle, which turns oxygen into the CO2 it releases
   • The electron transport chain, which forms water from the oxygen
9. 6.

   Read about only: the teacher handles the equipment. Kira reads a respirometer card of pea seeds. Which statement does the card support?

   • The germinating seeds created new energy, which is why they used oxygen
   • The seeds are plants, so the gas changes come from photosynthesis, not respiration
   • Germinating seeds respire more, since tube 1 used more oxygen and released more CO2
   • Dry seeds respire faster, since tube 2 used more oxygen

10. Glycolysis table (real data, from OpenStax Biology 2e)

    measure	per glucose
    ATP spent	2
    ATP made	4
    net ATP	2
    NADH made	2
    pyruvate made	2

11. 7.

    Milo reads the glycolysis table. Which statement does the table support?

    • Glycolysis nets 4 ATP, since the 2 ATP spent are not counted
    • Glycolysis nets 6 ATP, since 2 spent plus 4 made is 6
    • Glycolysis makes about 90 percent of the ATP, since it comes first
    • Glycolysis makes 4 ATP and spends 2, so the net is 2
12. 8.

    Real-data note: chemiosmosis makes about 90 percent of the ATP. Noah reads that chemiosmosis makes about 90 percent of the ATP from glucose. A model cell makes 20 ATP from one glucose. How are the 20 shared?

    • 10 from chemiosmosis and 10 from the other stages
    • 20 from chemiosmosis and 0 from the other stages
    • 18 from chemiosmosis and 2 from the other stages
    • 2 from chemiosmosis and 18 from glycolysis

13. Use this

    Flow diagram (model, not to scale), drawn inside a mitochondrion. Inputs in boxes on the left: 2 pyruvate (3 carbons each). Outputs in boxes on the right: CO2, amounts not shown. Stages shown in order: pyruvate oxidation, then the citric acid cycle. The 6 carbons of one glucose all end as CO2.

14. 9.

    Pia follows the 6 carbons of one glucose, and all 6 end up in CO2. Which statement about how the CO2 forms is right?

    • 6 CO2 form at the last stage, when the oxygen picks up carbon from glucose
    • 6 CO2 form: 3 in each of the 2 pyruvate steps and 0 in the citric acid cycle
    • 6 CO2 form: 2 in glycolysis in the cytoplasm and 4 in the electron transport chain
    • 6 CO2 form: 2 as pyruvate is oxidized and 4 in the citric acid cycle

15. ATP per glucose card (real data)

    source	ATP per glucose in aerobic respiration
    Judge and Dodd 2020	about 30 to 32
    OpenStax Biology 2e	the number varies

16. 10.

    Ren reads that the ATP yield per glucose varies. What can make the number vary from cell to cell?

    • The number of hydrogen ions pumped and how electrons enter the mitochondrion
    • The number of breaths the person takes in a minute
    • How much extra energy the cell creates beyond what glucose holds
    • Glycolysis nets 2 ATP in some cells and 30 ATP in others