Photosynthesis

Question 1

What is photosynthesis?

Answer 1

When plants make use of the sun’s energy to make food (glucose)

Question 2

What is the word and simple equation for photosynthesis?

Answer 2

Carbon dioxide + Water —> Glucose + Oxygen
6CO2 + 6H20 —> C6H12O6 + 6O2

Question 3

What are the limiting factors for photosynthesis?

Answer 3

. Carbon dioxide
. Light
. Temperature
. Water
. Chlorophyll

Question 4

What is the method for investigating the effect of light intensity on photosynthesis in pondweed?

Answer 4

1. Fill a boiling tube with 0.2% sodium hydrogen carbonate solution.
2. Freshly cut a 10 cm piece of pondweed and place it in the boiling tube with the cut end at the top.
3. Set up an LED lamp at a distance of 10 cm to the boiling tube and leave it to settle for five minutes.
4. Start the stopwatch and count the number of bubbles released in one minute.
5. Repeat twice and calculate the main number of bubbles.
6. Repeat steps 1 to 5 and alter distance of the lamp so it is 30cm, 40cm and 50cm away from the boiling tube.

Question 5

Why do we use sodium hydrogen carbonate solution in the pondweed practical?

Answer 5

This provides excess dissolved carbon dioxide for the plant to use in photosynthesis, so it is not a limiting factor

Question 6

What is an LED lamp used in the pondweed practical?

Answer 6

LED lamps produce less heat, and this reduces the effect of temperature on the experiment

Question 7

How do high light intensities slow the rate of photosynthesis?

Answer 7

. Saturation of the active sites in the enzyme, catalyzing the reaction.
. Bleaching of chlorophyll.

Question 8

How to calculate light intensity?

Answer 8

Light intensity = 1/distance squared

Question 9

How do farmers control conditions inside greenhouses to improve crop yields?

Answer 9

. Heating can be used to provide optimum temperatures for maximum plant growth.
. Artificial lighting, enhances the natural sunlight, especially overnight and on cloudy days.
. Extra carbon dioxide, gas can be pumped into the air inside the greenhouses.

Question 10

What are the uses of glucose in photosynthesis?

Answer 10

. To produce cellulose which strengthens the plant cell walls.
. To be converted into insoluble starch for storage inside cells or special area like roots or bulbs.
. To be converted into amino acids for protein synthesis. Glucose is combined with nitrate ions, absorbed in the soil. Specific amino acid joined in long chains to make a named protein.
. To produce fat or oil for storage. Seeds and nuts contain lots of fat or oil as an energy store.