Photosynthesis and Cellular Respiration Worksheet with Answers by Laney Lee

Let’s solve this step by step.

We’re comparing Cellular Respiration and Photosynthesis — two big processes in biology that are kind of opposites!

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Step 1: Where do they happen?

- Cellular Respiration happens in the mitochondria (the powerhouses of the cell).
- Photosynthesis happens in the chloroplasts (in plant cells, where sunlight is used to make food).

✔ So:
> Cellular Respiration → Mitochondria
> Photosynthesis → Chloroplasts

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Step 2: Energy – product or reactant?

Think about what each process *does*:

- Photosynthesis: Uses energy (sunlight) to make glucose. So energy is a reactant.
- Cellular Respiration: Breaks down glucose to release energy (ATP). So energy is a product.

✔ So:
> Cellular Respiration → Product
> Photosynthesis → Reactant

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Step 3: Oxygen – product or reactant?

- In photosynthesis, plants take in CO₂ and water, and release oxygen as waste → so oxygen is a product.
- In cellular respiration, organisms use oxygen to break down glucose → so oxygen is a reactant.

✔ So:
> Cellular Respiration → Reactant
> Photosynthesis → Product

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Step 4: Carbon Dioxide – product or reactant?

- Photosynthesis: Plants take in CO₂ to build glucose → reactant
- Cellular Respiration: Organisms produce CO₂ as waste when breaking down glucose → product

✔ So:
> Cellular Respiration → Product
> Photosynthesis → Reactant

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Step 5: Water – product or reactant?

This one can be tricky, but let’s think:

- Photosynthesis: Uses water + CO₂ → makes glucose + O₂ → so water is a reactant
- Cellular Respiration: Glucose + O₂ → makes CO₂ + H₂O + ATP → so water is a product

✔ So:
> Cellular Respiration → Product
> Photosynthesis → Reactant

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Step 6: Glucose – product or reactant?

- Photosynthesis: Makes glucose from CO₂ and water → product
- Cellular Respiration: Breaks down glucose to get energy → reactant

✔ So:
> Cellular Respiration → Reactant
> Photosynthesis → Product

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Step 7: What form is energy found in?

In both cases, the usable energy for cells is stored in ATP (adenosine triphosphate). But note:

- In photosynthesis, light energy is converted into chemical energy (glucose), which later becomes ATP during respiration.
- The question says: “In what form can you find energy in this reaction?”

For cellular respiration, the direct energy output is ATP.

For photosynthesis, the energy is stored in glucose (which will later be turned into ATP via respiration).

But looking at common worksheet answers, they often say:

> Cellular Respiration → ATP
> Photosynthesis → Glucose (or sometimes “chemical energy”)

However, since the blank says “in this reaction”, and photosynthesis produces glucose (which holds the energy), we’ll go with:

✔ So:
> Cellular Respiration → ATP
> Photosynthesis → Glucose

*(Note: Some teachers accept “chemical energy” for photosynthesis too — but glucose is more specific and matches the context.)*

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Now fill in the table:

| Takes place in which organelle? | CELLULAR RESPIRATION | PHOTOSYNTHESIS |
|---------------------------------------|----------------------|--------------------|
| ENERGY (product or reactant?) | Product | Reactant |
| OXYGEN (product or reactant?) | Reactant | Product |
| CARBON DIOXIDE (product or reactant?) | Product | Reactant |
| WATER (product or reactant?) | Product | Reactant |
| GLUCOSE (product or reactant?) | Reactant | Product |
| In what form can you find energy... | ATP | Glucose |

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Bonus: Chemical Equations (if needed)

You might also see these:

Photosynthesis:
6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂

Cellular Respiration:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

They’re basically backwards! That’s why they’re called opposite processes.

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Final Answer:

| Takes place in which organelle? | CELLULAR RESPIRATION | PHOTOSYNTHESIS |
|---------------------------------------|----------------------|--------------------|
| ENERGY | Product | Reactant |
| OXYGEN | Reactant | Product |
| CARBON DIOXIDE | Product | Reactant |
| WATER | Product | Reactant |
| GLUCOSE | Reactant | Product |
| Form of energy | ATP | Glucose |