PLANT PHYSIOLOGY
Az Agrármérnöki MSc szak tananyagfejlesztése TÁMOP-4.1.2-08/1/A-2009-0010
The light reactions of the photosynthesis
Photosynthesis inhibiting
herbicides
Overview
1. Photosynthesis, general concepts
2. Organization of the photosynthetic apparatus
3. Organization of light-absorbing antenna systems 4. Mechanism of electron transport
5. Proton transport and ATP synthesis in the chloroplast
6. Inhibitors of electron transport are effective
herbicides
1. Photosynthesis, general concepts
1.1. Light has both particle and wave characteristics 1.2. Photosynthetic pigments absorb the light
1.3. Absorption and action spectra
1.4. Oxygen-evolving organisms have two photosystems 1.5. Light drives the reduction of NADP and the formation
of ATP
1.6. NADPH and ATP are used for CO2 fixation
Light is a transverse electromagnetic wave, consisting of oscillating electric and magnetic fields
The electromagnetic spectrum
The solar spectrum and its relation to the absorption spectrum of chlorophyll
Molecular structure of some photosynthetic pigments
Light absorption and emission by chlorophyll
Absorption spectra of some photosynthetic pigments
Action spectrum compared with an absorption spectrum
Basic concept of energy transfer during photosynthesis
The rate of photosynthesis when red and far-red light are given together is greater than the sum of the rates when they are given apart
Z scheme of photosynthesis
2. Organization of the photosynthetic apparatus
2.1. The chloroplast is the site of photosynthesis 2.2. Thylakoids contain integral membrane proteins
2.3. Photosystems I and II are spatially separated in the thylakoid membrane
2.4. Anoxygenic photosynthetic bacteria have a single reaction center
Transmission electron micrograph of a chloroplast from pea (Pisum sativum)
Schematic picture of the overall organization of the membranes in the chloroplast
Organization of the protein complexes of the thylakoid membrane
Structures of the four main protein complexes of the thylakoid membrane
3. Organization of light-absorbing antenna systems
3.1. Antenna systems contains chlorophyll and are membrane associated
3.2. The antenna funnels energy to the reaction center 3.3. Many antenna pigment-protein complexes have a common structural motif
The excited-state energy of pigments increases with distance from the
Some energy is lost as heat, but almost all the excitations absorbed in the antenna complexes can be delivered to the reaction center
4. Mechanism of electron transport
4.1. Electrons from chlorophyll travel through carriers 4.2. The reaction center chlorophylls of the two
photosystems absorb at different wavelength
4.3. Water is oxidized to oxygen by photosystem II 4.4. There are several electron acceptors and donors between photosystem II and I
4.5. The photosystem I reaction center reduces NADP
The transfer of electrons and protons in the thylakoid membrane is carried out vectorially by four protein complexes
The water oxidizing clock
5. Proton transport and ATP synthesis in the
chloroplast
Chemiosmotic mechanism of photosynthetic ATP formation
Subunit composition of chloroplast F1F0 ATP synthase
Compiled crystal structure of chloroplast F1F0 ATP synthase
6. Inhibitors of electron transport are effective
herbicides
Chemical structure and mechanism of action of two important