PPt 1

• Formula for photosynthesis is: Light+Co2+H2o=organic carbon + o2
• e negative chain proteins are in the thylakoid membrane
• H plus ions are pumped from the stroma to the lumen
• Two functional parts of a photosystem are: Antenna complex and Reaction center.
• Photosystems are complex protein assemblages containing pigments.
• Photosystems


  Complex protein assemblages containing pigments
• Antenna complex


  A functional part of a photosystem
• Antenna complexes are stimulated by photons
• Reaction centers are oxidized to send electrons
• When exposed to photons, antenna complexes gain energy
• Energy from antenna complex moves to reaction center
• Electrons in a photosystem are not moving, only the energy is.
• Kinetic energy from absorbed photons excites the electrons, increasing potential energy.
• Energy from absorbed photons is partially lost as heat.
• Antenna Complex


  Large cluster of accessory pigments
• Accessory pigments of the Antenna Complex are carotenoids, flavonoids and chlorophyll-b
• The Antenna Complex has several pigments to increase the "range" of the antenna
• When winter comes, chlorophyll become less useful, some plants break it down to recycle its components.
• With only some accessory pigments left, leaves change color.
• Why do leaves change color in the fall? They only have some of their accessory pigments left.
• What does FRET stand for?

  Florescence resonance energy transfer
• How many pigments in the reaction center?

  1
• The pigment in the reaction center is called chlorophyll-a
• Chlorophyll-a is the only pigment to lose an electron
• Chlorophyll-a is the final target of the FRET process
• Chlorophyll-a is oxidized to reduce an electron carrier
• Chlorophyll-a was oxidized and then needs to be reduced to start the process again.
• Water is oxidized to reduce Chlorophyll-a
• Plants use two photosystems
• Each plant photosystem has two different peak absorptions
• Absorption of Photosystem 1

  700nm
• The light-dependent reactions use light energy to make two molecules needed for the next stage of photosynthesis: the energy storage molecule ATP and the reduced electron carrier NADPH
• ATP

  The energy storage molecule
• NADPH

  The reduced electron carrier
• Light reactions take place in the thylakoid membrane of organelles called chloroplasts.
• Absorption of photosystem 2

  680nm
• In the reaction center energy is transferred to P680, boosting an electron to a higher energy level
• The electron boosted to a higher energy level is passed to an acceptor molecule and is replaced by an electron from water.
• Splitting water gives O2, the air we breathe.
• Both photosystems react to light