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?

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

2. Read this first

   Use this

   Building-block chain, not to scale.

3. 2.

   Bo's bean plant stores sugar by joining glucose units into a starch piece of 4 units. Which description fits?

   • Neither: the glucose units link with no water change
   • Dehydration synthesis: each glycosidic bond forms and uses a water
   • Hydrolysis: each glycosidic bond forms and uses a water
   • Dehydration synthesis: each glycosidic bond forms and releases a water
4. 3.

   Esme eats a bowl of beans. Digestive enzymes split a protein chain of 5 amino acids into single amino acids. Which description fits?

   • Dehydration synthesis: a water is released at each peptide bond it breaks
   • Neither: the protein comes apart without water
   • Hydrolysis: a water is released at each peptide bond it breaks
   • Hydrolysis: a water is added at each peptide bond it breaks
5. 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
6. 5.

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

   146 waters
7. 6.

   Milo reads about a fat. One glycerol and three fatty acids join into a triglyceride. Which description of the new bonds is correct?

   • Three peptide bonds form and 3 waters are released
   • Three ester bonds form and 3 waters are used
   • Three ester bonds form and 3 waters are released
   • Four ester bonds form and 4 waters are released
8. 7.

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

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

9. 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.

10. 8.

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

    • Six glycosidic bonds form and 6 waters are released
    • Six peptide bonds form and 6 waters are released
    • Seven peptide bonds form and 7 waters are released
    • Six peptide bonds form and 6 waters are used
11. 9.

    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 S: 6 monomers but just 5 waters
    • Chain Q: 3 bonds but 4 waters
    • Chain P: 2 monomers but just 1 water
    • Chain R: 3 monomers but just 2 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 uses 5 waters, one for each of the 5 beads
    • Splitting releases 4 waters, as building does
    • Building used 4 waters, and splitting released 4
    • Splitting uses 4 waters, the same count that building released