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9th grade · Science · Unit 5 of 10

Photosynthesis & Respiration

How cells make and use energy

What your child practices

The reactants, products and location of photosynthesis and cellular respiration, why they are complementary, and how they link plants, animals and the carbon cycle.

Arizona Academic Standards learning standard: HS.L2U1.21 · photosynthesis and cellular respiration

How we explain it

Children can open this short lesson before they practice.

  1. Photosynthesis (in chloroplasts): carbon dioxide + water + light → glucose + oxygen.
  2. Cellular respiration (in mitochondria): glucose + oxygen → carbon dioxide + water + energy.
  3. The products of each are the reactants of the other, which cycles carbon.

Example: Which process releases oxygen: photosynthesis or respiration? Respiration uses oxygen. Photosynthesis gives it off. Answer: photosynthesis

Photosynthesis & Respiration in Arizona

In the Arizona Academic Standards, this is unit 5 of 10 in 9th grade Science, after Electrons & Compounds and before The Periodic Table.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Arizona Department of Education

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Where in a cell is most of the energy released by cellular respiration?

    • the nucleus
    • chloroplasts
    • the cell membrane
    • mitochondria

  2. Question 2

    Which gas released by photosynthesis do animals use in cellular respiration?

    • nitrogen
    • carbon dioxide
    • oxygen
    • hydrogen

  3. Question 3

    In 6 O₂, how many oxygen atoms are there altogether?

    answer box

  4. Question 4

    Why are photosynthesis and cellular respiration called complementary?

    • They both need light
    • They both make oxygen
    • The products of each are the reactants of the other
    • They both happen only in animals

  5. Question 5

    Which words summarize photosynthesis?

    • glucose + oxygen → carbon dioxide + water + energy
    • oxygen + water → carbon dioxide + glucose
    • carbon dioxide + water + light energy → glucose + oxygen
    • glucose + carbon dioxide → water + oxygen

  6. Question 6

    Which is an energy transformation in photosynthesis?

    • thermal energy to sound energy
    • chemical energy to light energy
    • light energy to chemical energy
    • kinetic energy to light energy

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