Overview Of Photosynthesis

Question 1

Stomata close when light is turned of
Explain advantage of this to the plant
(2)

Answer 1

1. Because water is lost through stomata
2. Closure prevents water loss /reduces
3. Maintain water content of cell

Question 2

Properties of chlorophyll light absorbance?

(1)

Answer 2

1. pigment reflects / not absorb green,yellow,orange light
2. Pigment absorbs red
3. Pigment absorbs blue or violet

Question 3

Describe the part played by chlorophyll in photosynthesis

3

Answer 3

1. Light energy is absorbed by chlorophyll
2. Raises energy level of electrons/ electrons excited
3. ATP formed

Question 4

Red seaweed lives under water at a depth of 2m. Suggest an advantage to the red seaweed of having other pigments in addition to chlorophyll
(2)

Answer 4

1. More wavelengths / colours absorbed
2. More efficient photosynthesis occur at these depths / low light intensity
3. Or more photosynthesis can occur when some wavelengths not present

Question 5

Give one dependent variable you could measure in order to determine rate of photosynthesis in an aquatic plant
(1)

Answer 5

Count number of bubbles / measure volume of gas / measure change in pH / carbon dioxide / hydrogen carbonate ions

Question 6

Explain the rate of CO2 exchange at compensation point

2

Answer 6

1. Change in CO2 exchange due to photosynthesis
2. Plants carry out photosynthesis and respiration
3. At compensation point rates of respiration and photosynthesis are same