Light Harvesting

• Light harvesting occurs in the thylakoids
• the chlorophyll and the accessory pigments are found in the thylakoid membranes of the chloroplast, they are grouped in clusters of several hundred molecules known as an antenna complex
• What does this image depict?

  the antenna complex in the thylakoids

  
• 1. a molecule of chlorophyll a, called the primary pigment, is situated at the base of the antenna complex in a region called the reaction centre
• 2. the whole antenna complex, harvests light over a range of wavelengths, due to the presence of different pigments with different absorption maxima
• 3. photons of light are absorbed throughout the complex and special proteins help pass the absorbed energy from one molecule to its adjacent molecule by the process of resonance transfer 
• 4. the energy is funnelled in the direction of the reaction centre until they reach molecules of the chlorophyll a in the reaction centre
• 5. for resonance transfer to take place, the molecules of the antenna complex have to be arranged in a regular structure, each antenna complex forms a photosystem
• 6. photosystem I is arranged around a chlorophyll a molecule with an absorption peak of 700nm, this photosystem is called P700
• 7. photosystem II is arranged around a chlorophyll a molecule with an absorption peak of 680nm, thus photosystem is called P680