B1.4

Question 1

How do the photosynthesis reactants enter a plant?

Answer 1

CO2 diffuses in via the stomata
Water enters via the roots in osmosis

Question 2

What is the equation for photosynthesis

Answer 2

Carbon dioxide + water -> glucose + oxygen
(light and chlorophyll(pigment inside chloroplasts) are also used)

Question 3

How does photosynthesis occur

Answer 3

Light energy splits water into hydrogen and oxygen
CO2 combines with hydrogen to make glucose

Question 4

What happens to extra glucose?

Answer 4

It is converted to starch e.g as a source of energy in the night where photosynthesis doesnt occur

Question 5

How to test for starch

Answer 5

Kill the leaf in boiling water,remove chlorophyll via boiling ethanol
Wash the leaf,put on a white tile and add iodine onto it
If there is starch iodine turns from orangey to blue/black

Question 6

How to prove oxygen is given off by photosynthesis

Answer 6

Place an upturned test tube above an aquatic plant and put in light. After the tube fills (with gas), put a glowing splint in and it should relight due to oxygen

Question 7

How to prove chlorophyll is needed for photosynthesis

Answer 7

Destarch a variegated leaf (only chlorophyll in some parts) and place in sunlight,then test for the presence of starch

Question 8

How to prove light is needed for photosynthesis

Answer 8

Destarch a leaf and cover part of it with black card.Place in sunlight,then remove the card and test for the presence of starch

Question 9

How to prove carbon dioxide is needed for photosynthesis

Answer 9

Put a destarched plant in a polyethene bag with a pot of soda lime( to absorb co2) .Place in sunlight,then test for presence of starch.

Question 10

How do light intensity and co2 affect rate of photosynthesis

Answer 10

Positive correlation,but they both level off after some time,meaning there is another limiting factor

Question 11

How does temperature affect photosynthesis rate?

Answer 11

Positive correlation,but after optimum temperature the enzymes denature and the rate quickly reduces

Question 12

What is the equation of rate?

Answer 12

1 over time

Question 13

What is the equation for light intensity?

Answer 13

Inverse square law, so

1 over distance from light source squared

Question 14

How can you alter factors to investigate their effect on photosynthesis

Answer 14

Light intensity - place a light source e.g lamp at different distances
Co2 concentration - add different masses of potassium hydrogen carbonate powder
Temperature - place apparatus at different temperature water baths

Question 15

What is the most common limiting factor of photosynthesis and why?

Answer 15

CO2 due to the lack of it in the atmosphere

Question 16

What is light intensity of a source placed 50cm from a pot?

Answer 16

50cm to m = 0.5
1 over 0.5 squared
1 over 0.25 = 4

Question 17

What are the three limiting factors affecting photosynthesis?

Answer 17

Carbon dioxide, light intensity and temperature

Question 18

Where does photosynthesis occur?

Answer 18

In the chloroplasts of the leaves and stem

Question 19

Is photosynthesis an example of an endothermic or exothermic reaction?

Answer 19

Endothermic

Question 20

What is the balanced equation for photosynthesis?

Answer 20

6CO2 + 6H2O → C6H12O6 + 6O2