Factors affecting photosynthesis

Question 1

What are the types of pigments found in chloroplasts?

Answer 1

Primary pigment and accessory pigments.

Question 2

What is the purpose of having different accessory pigments?

Answer 2

To absorb a wider range of wavelengths of light.

Question 3

Why is sodium hydrogen carbonate added?

Answer 3

To supply carbon dioxide for photosynthesis.

Question 4

What does the volume of gas produced indicate?

Answer 4

It’s assumed to be oxygen, so the volume of gas is proportional to the rate of photosynthesis.

Question 5

What are the controlled variables of this practical?

Answer 5

-Light intensity (distance from lamp)
-Amount of sodium hydrogen carbonate
-Time allowed for gas collection
-Temperature

Question 6

How is the light wavelength controlled?

Answer 6

By using different colored filters to cover one side of the beaker close to the lamp, covering the other side using aluminum foil.

Question 7

Outline the procedure to this practical.

Answer 7

1. Place a piece of pondweed in a beaker of water.
2. Cover one side of the beaker with the aluminium foil, and cover the other side
   of the beaker with one of the light filters.
3. Add half a spatula of sodium hydrogencarbonate to the water to provide
   carbon dioxide. Leave for 5 minutes.
4. Place the bench lamp a set distance from the beaker.
5. Set up the photosynthometer. Leave for 5 minutes.
6. Record the volume of gas produced during this time.
7. Replace the filter with another colour of filter and repeat the experiment

Question 8

Why is the greatest volume of gas produced when no filter is used?

Answer 8

Because the plant is exposed to all wavelengths of light, so more wavelengths can be absorbed.

Question 9

Why is the smallest volume of gas produced when a green filter is used?

Answer 9

Because green light is mostly reflected and not absorbed. This is also why chloroplasts appear green.