1. 2.9.U2 Visible light has a range of wavelengths with violet the shortest wavelength and red the longest.

2. 2.9.U3 Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours.

3. % of the maximum rate of photosynthesis
2.9.S1 Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis.
This shows the
% of the maximum rate of photosynthesis
(Edited by Chris Paine)

4. % of the maximum rate of photosynthesis
2.9.S1 Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis.
This shows the
% of the maximum rate of photosynthesis
(Edited by Chris Paine)

5. 2.9.S1 Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis.
When drawing both action and absorption spectra, the x-axis should be , with nanometers shown as the units (400 – 700).
The y-axis on the left should be the  % of the maximum rate of photosynthesis (0 – 100)
The y-axis of the right should be the  % absorption of light (0 – 100)
% of the maximum rate of photosynthesis

6. 2.9.S1 Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis.
The action spectrum of photosynthesis and absorption spectrum of chlorophyll overlap each other – this tells us that chlorophyll is the most important of the photosynthetic pigments.
Light at the blue end of the spectrum contains more energy than light at the red end.
UV radiation is higher energy still, but cannot be used. In fact, it causes cell damage and mutations.

7. What pigments can you find and identify in a leaf?
2.9.S3 Separation of photosynthetic pigments by chromatograph. (Practical 4)
What pigments can you find and identify in a leaf?
Gather leaves of different types and colors and use Paper Chromatography or Thin Layer Chromatography (TLC) to separate the pigments, including chlorophyll present in a leaf.
Thin layer chromatography for photosynthetic pigments
SAPS have published two (slightly) different protocols:
Simplified Bioknowledgy protocol based on the SaPS outline:
In the absence of equipment use the virtual lab and self-test quiz:

8. Rate of Photosynthesis
2.9.U6 Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis.
At high levels of light intensity further increases have no effect on the rate of photosynthesis. Therefore light intensity is not the limiting factor, another factor (e.g. temperature, CO2 concentration, enzymes or chloroplasts working at maximum efficiency) is limiting photosynthesis.
Rate of Photosynthesis
When light intensity is increased the rate of photosynthesis increases therefore it is the limiting factor at low levels.
Light intensity
Light intensity refers to the amount of light, of a given wavelength, which is available to the plant.

9. Rate of Photosynthesis
2.9.U6 Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis.
Another factor (e.g. temperature, light, enzymes working at maximum efficiency) is limiting photosynthesis as further increases in carbon dioxide do not increase the rate of photosynthesis.
CO2 is a substrate for the metabolic pathway hence the relationship is similar to how enzyme reactions are limited by substrate concentration.
Rate of Photosynthesis
When carbon dioxide concentration is increased the rate of photosynthesis increases therefore it is the limiting factor at low concentrations.
Carbon dioxide concentration

10. Rate of Photosynthesis
2.9.U6 Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis.
Photosynthesis is a metabolic pathway hence the relationship is similar to how enzyme reactions are affected by temperature.
After the optimum temperature enzymes denature rapidly causing a fast decrease in the rate of photosynthesis as temperature increases further.
Rate of Photosynthesis
As the temperature approaches the optimum the enzymes begin to denature (active site changes to become non-functional) causing the rate of photosynthesis to increase more slowly and eventually peak.
Increases in temperature give molecules more kinetic energy causing substrates to collide with active sites more frequently, this increases the rate of photosynthesis
Temperature

11. Placing the plant in a closed space with water.
2.9.S2 Design of experiments to investigate the effect of limiting factors on photosynthesis.
Placing the plant in a closed space with water.
CO2 reacts with the water producing bicarbonate and hydrogen ions, which of the solution > increased pH ->

12. Aquatic plants can be submerged in water in a closed space with a
2.9.S2 Design of experiments to investigate the effect of limiting factors on photosynthesis.
Aquatic plants can be submerged in water in a closed space with a
Alternatively gas volume can be measured by or by simply .
Oxygen probes can be used with terrestrial plants kept in closed environments to measure increases in oxygen concentration.

13. production can be (indirectly) measured by a change in a plant's .
2.9.S2 Design of experiments to investigate the effect of limiting factors on photosynthesis.
production can be (indirectly) measured by a change in a plant's
levels in a plant (glucose is stored as starch)
can be identified by staining with , this can be quantitated using a

14. 2.9.S2 Design of experiments to investigate the effect of limiting factors on photosynthesis.
Before designing an carrying out your own investigation what questions need to be asked and considerations need to be made?

15. The independent variable
2.9.S2 Design of experiments to investigate the effect of limiting factors on photosynthesis.
Before designing an carrying out your own investigation what questions need to be asked and considerations need to be made?
The independent variable
Only one limiting factor should be investigated at a time
The range of values should reflect conditions experienced by the organism
The range of values should allow the limiting factor to range from values that restrict photosynthesis to values that allow photosynthesis to happen at it’s optimum rate.
The increments should be sufficiently in size that a trend can be clearly detected

16. 2.9.S2 Design of experiments to investigate the effect of limiting factors on photosynthesis.
Before designing an carrying out your own investigation what questions need to be asked and considerations need to be made?
Dependent variable
An accurate method for measuring the rate of photosynthesis needs to be used.
Oxygen production per time unit is recommended.
Leaf discs are a successful and easy way to measure oxygen generation by leaves

17. 2.9.S2 Design of experiments to investigate the effect of limiting factors on photosynthesis.
Before designing an carrying out your own investigation what questions need to be asked and considerations need to be made?
The control variables
These should include the limiting factors not being investigated.
Other key control variables should include any factor that affects a metabolic pathway controlled by enzymes, e.g. pH.
Ambient light should be considered as it affects the wavelength and intensity of light absorbed by the organism.
The values chosen for the control variables should be close to their optimum values so that the control variables do not limit photosynthesis. (If the control variables limit photosynthesis it may not be possible to see the impact of the limiting factor being investigated)

18. The control variables - Nature of Science
Nature of Science: Experimental design - controlling relevant variables in photosynthesis experiments is essential. (3.1)
Before designing an carrying out your own investigation what questions need to be asked and considerations need to be made?
The control variables - Nature of Science
Explain why it is essential to control the limiting factors not being investigated.
Evaluate which of the identified reasons are the most important.

19. Photosynthesis creates oxygen gas as a by-product ( ).
2.9.A1 Changes to the Earth’s atmosphere, oceans and rock deposition due to photosynthesis.
Primordial Earth had a reducing atmosphere that contained (approx. 2%).
 Cyanobacteria (prokaryotes) containing first performed photosynthesis about
Photosynthesis creates oxygen gas as a by-product ( ).
Oxygen levels remained at 2% until about 750 million years ago (mya). From 750 mya until now there has been a significant rise to .
Oxygen generation also allowed the formation of an (O3). Ozone shielded the Earth from damaging levels of This, in turn, lead to the
Iron compounds in the oceans were oxidized:
The insoluble iron oxides precipitated onto the seabed.
Time and further sedimentation has produced called the banded iron formations.
Oxygen in the atmosphere lead to the production of oxidised compounds (e.g. CO2) in the .