ATP: the cell's energy carrier

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   Flow diagram (model, not to scale), drawn inside the cell membrane. Ari reads that one ATP's hydrolysis releases 7.3 kcal/mol and moving one sodium ion across a membrane takes 2.1 kcal/mol. How many whole sodium ions could that energy move?

   • 4 ions: 7.3 ÷ 2.1 = 3.5, and half an ion is rounded up to 4
   • 1 ion: each ATP is meant to move a single sodium ion
   • 9 ions: 7.3 + 2.1 = 9.4, and that is rounded down to 9
   • 3 ions: 3 × 2.1 = 6.3 fits in 7.3, but 4 × 2.1 = 8.4 does not

2. Read this first

   Use this

   Flow diagram (model, not to scale), drawn inside the cell. Inputs in boxes on the left: ATP; model reaction X. Outputs in boxes on the right: ADP and Pi; model reaction X done. A wavy arrow points out of the reaction: 14 kcal/mol released by ATP hydrolysis in a living cell. Each run of model reaction X needs 5 kcal/mol.

3. 2.

   Bo reads that ATP hydrolysis in a living cell releases 14 kcal/mol. A model reaction X needs 5 kcal/mol each time. How many whole runs of X can one ATP drive?

   • 9 runs: 14 − 5 = 9, and each run uses up one unit of 5
   • 3 runs: 14 ÷ 5 = 2.8, and the 0.8 is counted as a whole run
   • 0 runs: ATP releases energy, so it cannot drive anything
   • 2 runs: 2 × 5 = 10 fits in 14, but 3 × 5 = 15 is too much
4. 3.

   This is the first step of glycolysis. In the first step of glycolysis, a cell spends ATP to add a phosphate group to glucose. Esme asks why. What is the best reason?

   • Adding a phosphate to glucose needs energy, and ATP hydrolysis supplies it
   • ATP stores the glucose until the cell needs it later on
   • The ATP is used up for good once it gives away its phosphate
   • Adding a phosphate to glucose releases energy, so ATP is a spare
5. 4.

   Jun reads a model graph. At time 0 a cell stops rebuilding ATP while it keeps working. When does the ATP run out, and what does that show?

   • At 30 s: ATP is the cell's long-term store of energy
   • At 3 s: the ATP is gone for good, so the cell cannot recover
   • At 3 s: ATP is a short-term supply that must be rebuilt
   • At no point: ADP and Pi turn back into ATP on their own

6. ATP budget of a model cell (model data)

   measure	ATP molecules
   present at the start	40
   broken down each second	8
   rebuilt each second	5

7. 5.

   Kira reads a model ATP budget. The cell works for 4 seconds at these rates. How many ATP molecules are present at the end?

   • 60: 4 seconds × 5 rebuilt adds 20 to the 40, with nothing broken down
   • 52: each second 8 − 5 = 3 is gained, so 40 + 12 = 52
   • 8: 4 seconds × 8 broken down leaves 8, with nothing rebuilt
   • 28: each second 8 are broken down and 5 rebuilt, a net loss of 3

8. Use this

   Flow diagram (model, not to scale), drawn inside the cell. Inputs in boxes on the left: line 1: ATP and water. Outputs in boxes on the right: line 2: ADP, with 2 phosphate groups, and Pi; line 3: ADP and Pi leave the cell as waste; line 4: glucose breakdown later supplies energy to rebuild. A wavy arrow points out of the reaction: line 1: energy released.

9. 6.

   Milo's notebook describes what happens to ATP in a cell, in four lines. Which line has a flaw?

   • Line 3: ADP and Pi are rebuilt into ATP, not thrown away
   • Line 4: rebuilding ATP needs no energy, so line 4 is extra
   • Line 1: ATP should hold its energy for weeks, not release it
   • Line 2: ADP should have 3 phosphate groups, like ATP
10. 7.

    Flow diagram (model, not to scale), drawn inside the cell. Noah's notebook shows ATP and water becoming ADP and Pi, with a wavy arrow into the reaction labeled energy needed. What is the flaw?

    • The wavy arrow should point out: breaking ATP down releases energy
    • Water should be an output, since hydrolysis releases water
    • The arrow is right: making ADP and Pi from ATP needs an energy input
    • The ADP box should show 3 phosphate groups to match ATP

11. ATP in a working model cell (model data)

    time (s)	ATP present	ATP broken down each second	ATP rebuilt each second
    0	60	12	12
    10	60	12	12
    20	60	12	12

12. 8.

    Pia says the amount of ATP stayed at 60, so the cell used none. What is the flaw in that claim?

    • A steady amount shows the ATP was stored away in the cell, not used
    • The amount should rise, because using ATP makes more of it
    • A steady amount can mean ATP is rebuilt as fast as it is used
    • The amount should fall, because used ATP is gone for good

13. Use this

    Flow diagram (model, not to scale), drawn inside the cell. No wavy arrow label is drawn. No wavy arrow labels are drawn.

14. 9.

    Tala's friend says rebuilding ATP is what releases the energy a cell uses for work. Which reply is correct?

    • Agree: joining the third phosphate to ADP releases energy
    • Disagree: rebuilding releases energy, and breaking takes it in
    • Disagree: rebuilding takes energy in; breaking ATP down releases it
    • Agree: ADP and Pi make the energy by themselves

15. ATP made during glucose breakdown (real data, from OpenStax Biology 2e)

    process	share of the ATP	where it happens
    chemiosmosis	90 percent	mitochondria in a eukaryotic cell
    substrate-level phosphorylation	a few ATP molecules	steps of the glucose pathways

16. 10.

    Zee reads that the mitochondria in a model muscle cell stop working. Which prediction fits the card?

    • ATP rebuilding falls sharply, since 90 percent of the ATP from glucose is made in mitochondria
    • ATP rebuilding stays the same, since stored ATP lasts for months
    • ATP rebuilding stays the same, since ADP and Pi make energy alone
    • ATP rebuilding stops at once, since the ATP is used up for good