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2.9 Photosynthesis

Path:

Nature of science:
Experimental design—controlling relevant variables in photosynthesis experiments is essential. (3.1)

Understandings:

Photosynthesis is the production of carbon compounds in cells using light energy.
Visible light has a range of wavelengths with violet the shortest wavelength and red the longest.
Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours.
Oxygen is produced in photosynthesis from the photolysis of water.
Energy is needed to produce carbohydrates and other carbon compounds from carbon dioxide.
Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of photosynthesis.

Applications and skills:

Application: Changes to the Earth’s atmosphere, oceans and rock deposition due to photosynthesis.
Skill: Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis.
Skill: Design of experiments to investigate the effect of limiting factors on photosynthesis.
Skill: Separation of photosynthetic pigments by chromatograph. (Practical 4)

Guidance:

Students should know that visible light has wavelengths between 400 and 700 nanometres, but they are not expected to recall the wavelengths of specific colours of light.
Water free of dissolved carbon dioxide for photosynthesis experiments can be produced by boiling and cooling water.
Paper chromatography can be used to separate photosynthetic pigments but thin layer chromatography gives better results.

Utilization:
Syllabus and cross-curricular links:
Biology
Topic 2.5 Enzymes

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