THYLAKOID REACTIONS

1
THYLAKOID REACTIONS

• Absorption
• Energy Transfer
• 1. Energy of Photon transferred to an Electron
• P ---gt e-
• 2. All energy of Photon absorbed by Electron
• P ---gt e-
• e- excited electron
• 3. Photon ceases to exist
• 4. Energy of Electron increased by the amount of
  energy of the Photon that was absorbed

2
Absorption
3
Absorption

• 5. Electron moves further away from nucleus
• 6. Energy lost when electron returns to the
  Ground State
• a. Heat - longer wavelength (IR)
• b. Light - Fluoresence
• photons of longer wavelength
• c. Photochemistry
• Transfer to another electron
• different molecule
• e- ---gt e- ---gt e

4
Photochemistry

• Carbon Atom (6e-)
• Orbitals
• 1S 2 e-
• SP3 Hybrid (4e-)
• 2S
• 2Px
• 2Py
• 2Pz
• 4 Shared e-
• All equal energy

5
Molecular Structure

• Organic Bonds
• Sigma (s)
• Single Bonds
• H-H, C-H, C-C, C-N, etc.
• Pi (?)
• Double bonds
• CO, CC, etc.
• Conjugated Double Bonds
• CC-CC-CC

6
Conjugated Double Bonds

• Electron Clouds
• Conjugated Double Bonds
• Alternating sigma and pi bonds
• Share Electrons Equally (fused orbitals)
• Very Dense Electron Clouds
• Pigment Molecules

7
Chlorophylls
Chromophore
Protein
Phytol Chain
8
Pigment Molecules

• 1. Chlorophylls
• a. Chromophore (color carrier)
• Conjugated double bonds
• Closed cycle of 4 rings
• 4 Nitrogens in center
• Metal attached to Nitrogens
• Magnesium (Mg)

9
Pigment Molecules

• b. Phytol Chain
• long hydrocarbon chain
• C20H39
• c. Protein
• Chromophore Covalently Linked
• Attached to Thylakoid Membrane

10
Carotenoids

• 2. Carotenoids (Carrots)
• a. beta-carotene
• reduced (orange)
• no oxygen
• b. Lycopene (red)
• Non Cyclic
• c. Retinal
• ½ ß-Carotene
• Vitamin A

11
Carotenoids

• d. Xanthophylls
• Oxidized ß-carotene
• Lutein - Yellow Leaves Flowers
• Rhodoxanthin - Red Taxus Berries
• Caprorubrum - Red Peppers

12
Carotenoids
(OH)
(OH)
Lutein
13
Flavonoids

• 3. Flavonoids
• UV- Absorption
• Water Soluble Pigments
• In Vacuole
• Anthocyanin
• Poinsettia

14
Absorption Spectra
15
First Action Spectrum
16
Action Spectrum
17
Chloroplast
18
Pigment Complexes

• Complexes
• Photosystem I and Photosystem II
• a. Light Harvesting Complex
• b. Core Complex
• c. Reaction Center
• 10 - 16 Chromophores per Protein
• 6 - 8 Proteins per Complex
• 1,000's of Complexes per Chloroplast

19
Energy Transfer
Core Complex
Light Harvesting Complex
20
Energy Transfer

• A. Light Harvesting Complexes (LHC)
• (Antenna Complexes)
• Chl a, Chl b, Carotenoid
• B. Core Complexes (CC)
• Chl a
• C. Reaction Centers (RC) P680 P700

Core Complex
Chla
21
Light Harvesting Complexes

• 1. Photosystem II (LHCII)
• a. Beta-carotene, Lutein, etc.
• blue light absorption
• photoprotection of chlorophylls
• b. 40-60 Chlorophyll a (chl a)
• c. 40-50 Chlorophyll b (chl b)
• d. 4-6 Proteins
• polypeptides associated with chl a and chl b

22
LHCII
23
LHC II Structure
24
Photosystem Complexes
25
Core Complexes

• 1. Photosystem II (CCII)
• all chl a
• 40-60 chl a molecules
• associated protein (CP43 CP47)
• water splitting enzyme (Mn)
• 2. Photosystem I (CCI)
• all chl a
• 90-120 chl a molecules
• associated protein

26
Reaction Centers

• 1. Photosystem II (RCII)
• Two special chl a molecules
• P680
• associated proteins (D1 and D2)
• electron acceptors (Qa Qb)
• 2. Photosystem I (RCI)
• Two chl a molecules
• P700
• associated proteins
• electron acceptors (A0 and A1)

27
Core Complex PS II
28
Photosystem I
29
Photosystem II
30
Electron Transport Chain
2H
Qb-
2e-
P
Qa-
P
P680
31
Photosystem I
PC-
32
Z Scheme
33
Electron Transport Chain
34
Thylakoid ATPase
35
Energy Capture

• Thylakoid Lumen
• 2 H2O 4 H O2
• PQH2 2 H
• Total 6H per O2
• Thylakoid Stroma
• Total per O2
• 6 ATP
• 4 NADPH 2 H

36
Chloroplast
37
Thylakoid Complex Structure
CCII
CCI
38
Thylakoid Complexes

• PSII
• LHCII,CCII, RCII- P680
• H2O Split
• Elec.Trans.Chain
• PQH2, Cytb/f, PC
• PSI
• LHCI,CCI,RCI,P700
• NADP Reductase
• ATPase