Topic 6 - Photosynthesis

Question 1

What form of energy do plants use to make glucose

Answer 1

Energy from the sun or sunlight

Question 2

Where does photosynthesis occur and what happens there?

Answer 2

Inside chloroplasts which contain chlorophyll- a green pigment that absorbs light

Question 3

What is the word equation for photosynthesis?

Answer 3

Light
Carbon dioxide + water ————–> Glucose + Oxygen
chlorophyll

Question 4

PRACTICAL: THE EFFECT OF LIGHT INTENSITY ON THE RATE OF PHOTOSYNTHESIS

Answer 4

1) The gas syringe should be empty and sodium hydrogencarbonate should be added to the water to make sure the plant has enough carbon dioxide.
2) A source of white light (a lamp) is placed at a specific distance from the plant
3) The pondweed is left to photosynthesis for a set amount of time
4) As it photosynthesises, oxygen will be collected in the gas syringe, accurately measuring the volume of oxygen produced
5) Experiment is repeated with the light source at different distances. The rate of oxygen produced at each distance can be calculated using vol/time taken
6) Variables that could affect results: temperature controlled by putting flask in water bath; carbon dioxide concentration by using set volume of sodium hydrogencarbonate to set volume of water.

Question 5

What are the 3 limiting factors of photosynthesis?

Answer 5

Concentration of carbon dioxide, temperature and light intensity

Question 6

How do these factors limit photosynthesis?

Answer 6

1) Not enough light slows done the rate of photosynthesis - light intensity ∝ 1/distance
2) Too little carbon dioxide also slows it down
3) The temperature has to be just right- at low temperatures, the enzymes work too slow and if its too hot then the enzymes denature