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
   • 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

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?

   • 2 runs: 2 × 5 = 10 fits in 14, but 3 × 5 = 15 is too much
   • 0 runs: ATP releases energy, so it cannot drive anything
   • 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
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. 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?

   • 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
   • 60: 4 seconds × 5 rebuilt adds 20 to the 40, with nothing broken down

8. Use this

   Flow diagram (model, not to scale), drawn inside the cell. Inputs in boxes on the left: glucose, amount not shown. Outputs in boxes on the right: energy extracted: 17 energy units (model data); energy released as heat: the rest. No wavy arrow label is drawn. OpenStax: glucose pathways extract about 34 percent of the energy in glucose.

9. 6.

   Luz reads that glucose-breakdown pathways extract about 34 percent of the energy in glucose and release the rest as heat. A model cell extracts 17 energy units. About how many units did the glucose hold?

   • About 83, because 17 plus the 66 percent lost is 83
   • About 17, because the cell extracts the full amount
   • About 6, because 34 percent of 17 is about 6
   • About 50, because 17 is about 34 percent of 50

10. 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.

11. 7.

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

    • Line 4: rebuilding ATP needs no energy, so line 4 is extra
    • Line 2: ADP should have 3 phosphate groups, like ATP
    • Line 3: ADP and Pi are rebuilt into ATP, not thrown away
    • Line 1: ATP should hold its energy for weeks, not release it
12. 8.

    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?

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

13. 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

14. 9.

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

    • 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
    • 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

15. 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

16. 10.

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

    • Disagree: ATP is for immediate work, so plants store sugar as starch
    • 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