Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Pigments are substances that have an ability to absorb light at specific wavelengths.
Chromatographic separation of leaf pigments shows that the color we see in leaves is due to four pigments: Chlorophyll (bright or blue-green), Chlorophyll (yellow-green), Xanthophylls (yellow), and Carotenoids (yellow to yellow-orange).
Chlorophyll is the primary pigment involved in the conversion of light energy into chemical energy. It shows maximum absorption in the blue and red regions of the visible spectrum.
Accessory pigments (Chlorophyll , xanthophylls, and carotenoids) absorb light and transfer the energy to chlorophyll . They also protect chlorophyll from photo-oxidation.
An Absorption Spectrum is a graph representing the relative absorption of different wavelengths of light by a specific pigment.
An Action Spectrum is a graph that depicts the relative rates of photosynthesis at different wavelengths of light, usually measured by oxygen release.
The action spectrum of photosynthesis corresponds closely to the absorption spectrum of chlorophyll , indicating that it is the chief pigment.
📐Formulae
💡Examples
Problem 1:
Which wavelengths of the visible spectrum show the maximum rate of photosynthesis, and which pigment is primarily responsible?
Solution:
The maximum rate of photosynthesis occurs in the blue (approx. - nm) and red (approx. - nm) regions of the spectrum. Chlorophyll is primarily responsible.
Explanation:
The action spectrum of photosynthesis peaks in the blue and red regions, which coincides with the absorption peaks of Chlorophyll .
Problem 2:
Explain the role of carotenoids in preventing photo-oxidation.
Solution:
Carotenoids act as 'shields' for Chlorophyll .
Explanation:
In high light intensities, can become excited and form singlet oxygen (), which is highly reactive and can damage the plant. Carotenoids quench this energy and dissipate it as heat, protecting the photosynthetic apparatus.