Question 1

What do plants need to make their own food?

Accepted Answer

Plants need sunlight, water, and carbon dioxide (CO₂) to make their own food through photosynthesis.

Question 2

What gas do plants release during photosynthesis?

Accepted Answer

Plants release oxygen (O₂) as a byproduct of photosynthesis.

Question 3

Where does photosynthesis take place in a plant cell?

Accepted Answer

Photosynthesis takes place in the chloroplasts, which contain the green pigment chlorophyll.

Question 4

What happens to the rate of photosynthesis as light intensity increases?

Accepted Answer

As light intensity increases, the rate of photosynthesis increases until it reaches a maximum plateau.

Question 5

Why does the rate of photosynthesis level off at high light intensities?

Accepted Answer

The rate levels off because other factors (like CO₂ concentration or temperature) become limiting factors.

Question 6

What is the equation for photosynthesis?

Accepted Answer

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

Question 7

At what light intensity does the rate of photosynthesis reach its maximum in the Gizmo?

Accepted Answer

In the Gizmo simulation, the rate typically plateaus around 80–100% light intensity, after which additional light produces no further increase.

Question 8

What unit is used to measure the rate of photosynthesis in the Gizmo?

Accepted Answer

The rate of photosynthesis is measured in O₂ bubbles per minute, representing oxygen released by the plant.

Question 9

How does increasing CO₂ concentration affect the rate of photosynthesis?

Accepted Answer

Increasing CO₂ concentration increases the rate of photosynthesis because CO₂ is a raw material used in the Calvin cycle to produce glucose.

Question 10

What happens to photosynthesis if CO₂ is removed from the environment?

Accepted Answer

Without CO₂, photosynthesis cannot occur because carbon dioxide is essential for building glucose molecules.

Question 11

Which factor — light intensity or CO₂ concentration — has a greater effect on photosynthesis rate at low levels?

Accepted Answer

At low levels, both are limiting factors. Light intensity tends to have a more immediate effect at very low levels, but CO₂ becomes the primary limiting factor once light is sufficient.

Question 12

How does temperature affect the rate of photosynthesis?

Accepted Answer

Photosynthesis rate increases with temperature up to an optimal point (around 25–35°C for most plants), then decreases sharply as enzymes denature at high temperatures.

Question 13

Why does photosynthesis slow down at very high temperatures?

Accepted Answer

At high temperatures, the enzymes involved in photosynthesis (such as RuBisCO) begin to denature, losing their shape and function, which slows the reaction.

Question 14

What is the optimal temperature range for photosynthesis in the Gizmo?

Accepted Answer

The optimal temperature in the Gizmo is typically around 25°C, where the rate of photosynthesis is highest before enzyme activity declines.

Question 15

What are the three limiting factors of photosynthesis explored in this Gizmo?

Accepted Answer

The three limiting factors are: (1) light intensity, (2) CO₂ concentration, and (3) temperature.

Question 16

A plant is placed in bright light but photosynthesis is still slow. What could be the limiting factor?

Accepted Answer

If light is not the issue, the limiting factor could be low CO₂ concentration or a temperature that is too low or too high for optimal enzyme activity.

Question 17

How do the products of photosynthesis benefit other organisms?

Accepted Answer

Glucose produced by photosynthesis provides energy for the plant and for animals that eat the plant. Oxygen released is used by most living organisms for cellular respiration.

Question 18

Compare the rates of photosynthesis at 10% vs 100% light intensity. What does this tell you?

Accepted Answer

At 10% light intensity the rate is much lower than at 100%, demonstrating that light is a key limiting factor. This shows a direct relationship between light availability and photosynthetic output up to the saturation point.

Photosynthesis Lab Answer Key

Prior Knowledge Questions

Activity A – Light Intensity

Activity B – CO₂ Concentration

Activity C – Temperature

Assessment Questions

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