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?

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

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?

   • 0 runs: ATP releases energy, so it cannot drive anything
   • 3 runs: 14 ÷ 5 = 2.8, and the 0.8 is counted as a whole run
   • 2 runs: 2 × 5 = 10 fits in 14, but 3 × 5 = 15 is too much
   • 9 runs: 14 − 5 = 9, and each run uses up one unit of 5
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 releases energy, so ATP is a spare
   • ATP stores the glucose until the cell needs it later on
   • Adding a phosphate to glucose needs energy, and ATP hydrolysis supplies it
   • The ATP is used up for good once it gives away its phosphate
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 no point: ADP and Pi turn back into ATP on their own
   • At 3 s: ATP is a short-term supply that must be rebuilt

6. 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.

7. 5.

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

   • Line 2: ADP should have 3 phosphate groups, like ATP
   • Line 1: ATP should hold its energy for weeks, not release it
   • Line 3: ADP and Pi are rebuilt into ATP, not thrown away
   • Line 4: rebuilding ATP needs no energy, so line 4 is extra
8. 6.

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

9. 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

10. 7.

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

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

11. Where cells keep energy (real data, from OpenStax Biology 2e)

    form of energy	how it is used
    ATP	immediate work
    starch in plants	stored glucose
    fats	long-term storage

12. 8.

    Ren says a plant should keep its winter energy as ATP in every cell. Which reply is best?

    • Disagree: plants keep their winter energy as ADP, which holds more than ATP
    • Disagree: plants cannot store energy in any form
    • Agree: ATP is a stable long-term store, like starch
    • Disagree: ATP is for immediate work, so plants store sugar as starch

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

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