, Learning objective
12.1.2.2 Explain the absorption of light by chlorophyll
Success criteria:
• understand the process of preparing plant tissue
• describing and detailing the technique of paper chromatography as a method of separating
individual plant pigments contained in plant tissue extracts containing pigment blends
• identify the presence of different pigments in chlorophylls
• calculate and explain Rf values which are affected by the solubility and molecular size of
the pigments
• describe red fluorescence results based on a practical
• describe how higher energy levels play a role in chlorophyll length of light wave
• establish the relationship between the structure and function of chlorophyll
• compare and contrast haemoglobin and chlorophyll
• describe and explain the absorption of light by different types of chlorophyll
• outline and explain the process of paper chromatography related to light spectrometry
• differentiate between chlorophyll a and b light absorbance
• use the spectra of molecules to establish the relationship between destruction and energy
of wave absorption
• discuss how pigment concentration relates to photosynthesis and wavelength absorption
• differentiate absorption of wavelengths in carotenoids and chlorophyll types
• compare results of thin layer chromatography based on changes in seasons and
wavelength absorbance
, Discuss the inner working of
photosystems.
Photosynthetic pigments are
arranged in structures called
photosystems. These can
also be referred to as light
harvesting systems or
reaction centres
Photosystems – are found in
the thylakoid membranes
(thylakoids (grana) and
lamellae)
They are transmembrane
protein complexes.
, Describe what photosynthetic
pigments are.
All have a similar structure but all absorb different wavelengths of light.
Pigments include:
• chlorophyll a Primary photosynthetic pigments - they
reflect green light and absorb red light
• chlorophyll b
Both are a category of carotenoids - they
• Xanthophyll reflect orange/yellow light and absorb blue
• Carotene light
• Pheophytin (a and b) – electron carriers, part of the
electron transport chain
Accessory pigments – absorb the wavelengths of light that are not easily
absorbed by chlorophyll and are not directly involved in the light
dependent reactions. They channel more captured light energy to
chlorophyll so more electrons can be excited.