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

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

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

   • Four ester bonds form and 4 waters are released
   • 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
7. 7.

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

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

8. 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.

9. 8.

   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 released
   • Seven peptide bonds form and 7 waters are released
   • Six peptide bonds form and 6 waters are used
   • Six glycosidic bonds form and 6 waters are released
10. 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 R: 3 monomers but just 2 waters
    • Chain S: 6 monomers but just 5 waters
    • Chain Q: 3 bonds but 4 waters
    • Chain P: 2 monomers but just 1 water

11. 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

12. 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
    • Splitting uses 4 waters, the same count that building released
    • Building used 4 waters, and splitting released 4