How small molecules join into big ones

Answer Key - Grade 9 Science Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   Building-block chain, not to scale. 3 water beads arrive, one at each bond. Ari eats a piece of bread. Enzymes break a 4-unit piece of its starch into single glucose units. Which description fits?

   • Neither: starch comes apart without water
   • Hydrolysis: water is released as each bond splits
   • Dehydration synthesis: water is released as each bond splits
   • Hydrolysis: water is added across each bond it splits
2. 2.

   Building-block chain, not to scale. Bo's bean plant stores sugar by joining glucose units into a starch piece of 4 units. Which description fits?

   • Hydrolysis: each glycosidic bond forms and uses a water
   • Neither: the glucose units link with no water change
   • Dehydration synthesis: each glycosidic bond forms and uses a water
   • Dehydration synthesis: each glycosidic bond forms and releases a water
3. 3.

   A cell builds human cytochrome c, one chain of 104 amino acids. How many water molecules are released as the chain forms, Jun?

   103 waters
4. 4.

   Digestive enzymes split one insulin A chain, 21 amino acids long, all the way into single amino acids. How many waters are used, Kira?

   20 waters
5. 5.

   A cell builds the beta chain of hemoglobin, 147 amino acids long, by dehydration synthesis. How many waters are released, Luz?

   146 waters
6. 6.

   Noah stirs table sugar into tea. Sucrose is one glucose joined to one fructose. Which description of the new bond is correct?

   • Two glycosidic bonds form and 2 waters are released
   • One glycosidic bond forms and 1 water is released
   • One ester bond forms and 1 water is released
   • One glycosidic bond forms with no water involved

7. Read this first

   Use this

   Building-block chain, not to scale. 7 amino-acid beads in a row, each neighbor pair joined by a peptide bond. 6 water beads drift away, one at each join.

8. 7.

   Pia's cell links 7 amino acids into a short chain. Which description of the new bonds is correct?

   • Six peptide bonds form and 6 waters are used
   • Six peptide bonds form and 6 waters are released
   • Six glycosidic bonds form and 6 waters are released
   • Seven peptide bonds form and 7 waters are released
9. 8.

   Ren tests a rule: each bond formed releases one water. The table shows four chains built by joining beads. Which chain breaks the rule?

   • Chain R: 3 monomers but just 2 waters
   • Chain P: 2 monomers but just 1 water
   • Chain S: 6 monomers but just 5 waters
   • Chain Q: 3 bonds but 4 waters

10. Four chains split completely by hydrolysis (model data)

    chain	monomers made	waters used
    W	3	3
    X	6	7
    Y	8	8
    Z	10	9

11. 9.

    Tala tests a rule: each bond split uses one water. The table shows four chains split into single monomers. Which row follows the rule?

    • Chain Y: 8 monomers and 8 waters
    • Chain X: 6 monomers and 7 waters
    • Chain Z: 10 monomers and 9 waters
    • Chain W: 3 monomers and 3 waters

12. One chain of 5 beads, built and then split (model data)

    reaction	water change	waters
    building by dehydration synthesis	released	4
    splitting by hydrolysis	used	4

13. 10.

    Zee compares building and splitting the same chain of beads. Which statement matches the table?

    • Splitting releases 4 waters, as building does
    • Splitting uses 5 waters, one for each of the 5 beads
    • Splitting uses 4 waters, the same count that building released
    • Building used 4 waters, and splitting released 4