SB6b

Question 1

What are the major limiting factors for photosynthesis?

Answer 1

1. CO2 concentration (fewer CO2 molecules in mountains)
2. Light Intensity
3. Water
4. Temperature

Question 2

Why would the plant cells be damaged if temperatures were too high?

Answer 2

If it gets too hot (above 40 °C), the enzymes needed for
photosynthesis begin to denature.

Question 3

Can we see if plants are photosynthesising? how?

Answer 3

Yes,
We can test for:
 Production of glucose or oxygen.
 Decrease of carbon dioxide.

Question 4

What is a Variegated leaf?

Answer 4

Variegated leaves have pale parts, which
do not contain chlorophyll.

Question 5

Explain the variegated leaf experiment. (10)

Answer 5

1.Keep the plant in the dark for 3 days
2.Place the leaf in the sunlight for 6 hours
3.Detach a leaf and mark the green areas
4.Trace the leaf and the green borders on a butter paper
5.Boil the leaf for few minutes
6.Place the boiled leaf in alcohol
7.Place the beaker in a water bath
8.Heat till alcohol boils
9.Dip the leaf in distilled iodine solution
10.Take out the leaf and rinse
11.Compare leaf with the tracing from earlier

Question 6

State the test for photosynthesis.

Answer 6

1.Leave the two similar variegated plants in the dark for 24 hours
2.Put one plant in the light and leave the other in the dark for another 24 hours
3. Place the leaf from each plant in a beaker and submerge them underwater using forceps
4. Place the beakers in a water bath that’s close to boiling
5. Pour the water out make sure the leaf stays in the beaker
6. Add ethanol to thew beakers Place the beakers back in to the water bath
7. Pout the coloured ethanol out
8.Add hot water into the beaker
9. Using forceps place the leaves on a petri dishes
10.Add plenty of iodine solution and observe for colour change

Question 7

How do you make the test for photsynthesis more Reliable?

Answer 7

repeat experiment at least three more times.

Question 8

How do you make the test for photsynthesis more Accurate?

Answer 8

– instead of counting bubbles use a syringe to collect
gas.
o Bubbles are different sizes
o May miss a few (human error)

Question 9

How do you make the test for photsynthesis more Valid?

Answer 9

control and keep all variable the same
o Same water temperature
o Same mass / length of plant + species / type of plant
o Same lamp / bulb
o Same carbon dioxide levels

Question 10

What is a Linear relationship?

Answer 10

straight line on the graph
As one variable increases the other increases too

Question 11

What does it mean when it says the graph is Directly proportional?

Answer 11

when the line passes through the point of origin
As one variable doubles, the other doubles too

Question 12

What is the equation to calculate the new light intensity when the distance changes?

Answer 12

old light intensity x old distance
new light intensity = ———————————————
new distance