Lesson 4 pigments
Transcript of Lesson 4 pigments
Photosynthetic pigments...
Learning objectives...•The roles of pigments in light
harvesting
http://www.teachers-direct.co.uk/resources/quiz-busters/quiz-busters-game.aspx?game_id=28036
• Photon of light strikes accessory pigment• Light energy is passed down to the reaction centre• 2 electrons are excited and released from the Mg atom
PSI = chlorophyll a P700nmPSII = chlorophyll b P680nm
Light is absorbed by individual chlorophylls in the light-harvesting complexes
Energy is transferred from one pigment to another via Resonance Energy Transfer
This transfer funnels the energy to a reaction centre
where electron transfer starts
Energy transfer in light-harvesting complexes
Low resolution structures of photosystem II
• electron microscopy
• membrane preparations
• single particles - negative stain
arrangement in thylakoid membrane
Photosystem II - at 3.5Å resolution
Comparing Photosystem I and Photosystem II
Use Page 61 to compare photosystem I and photosystem II
Prosthetic groups of PSII core
• The 2 most important pigments involved in photosynthesis are chlorophylls and (1). The chlorophyll molecule consists of a complex ring called a (2) ring that is attracted to water so called (3). It also has a long lipid-soluble chain that is repelled by water and therefore called (4). Chlorophyll takes in certain wavelengths more than others. A graph of the amount of light taken in by different pigments is called the (5). Chlorophyll a acts as the (6) centres at the heart of the a complex of pigments molecules and associated (7) know collectively as a photosystem. Around the central chlorophyll molecule are (8) pigments that form a unit called a (9). Photosystem I has chlorophyll that absorbs light of wavelength (10) and found mostly in the (11) of the chloroplast. Photosystem II has chlorophyll that absorbs light of wavelength (12) and is found mainly in the (13).