Original video: https://youtu.be/zFW9OvhQt8k
Delivered on: 16 OCTOBER 2023
This video dives deep into the intricate mechanisms of photosynthesis, focusing on the Z-scheme and the electron transport chain. 🌿 We'll break down the complex processes that drive light-dependent reactions, converting light energy into chemical energy.
What you'll learn:
Midpoint Potential and Electron Flow: Understand the concept of midpoint potential and how it dictates electron flow through the Z-scheme, from water to NADP+.
Photosystem II (PSII): Explore the structure and function of PSII, including its role in water oxidation and plastoquinone reduction.
Cytochrome b6f Complex and Q Cycle: We'll unravel the intricacies of the Q cycle, proton translocation, and electron transfer within the cytochrome b6f complex.
Photosystem I (PSI): Discover how PSI utilizes light energy to reduce NADP+ with the help of ferredoxin and NADP reductase.
ATP Synthesis: Learn how proton motive force generated during electron transport drives ATP synthesis via ATP synthase.
Light Absorption and Excited States: We'll examine the absorption spectrum and action spectrum of chlorophyll, and discuss the different types of excited states.
Herbicide Action: Understand how herbicides can interfere with photosynthetic electron flow, with examples like paraquat.
9.5 Organization of Light-Absorbing Antenna Systems
The antenna system funnels energy to the reaction center (Figure 9.16).
Light-harvesting proteins of both photosystems are structurally similar (Figure 9.17).
9.6 Mechanisms of Electron Transport
The Z scheme illustrates the flow of electrons from H2O to NADP+ through carriers in PSII and PSI (Figures 9.12, 9.18).
Three large protein complexes transfer electrons: PSII, the cytochrome b6f complex, and PSI (Figures 9.15, 9.19).
PSI reaction center chlorophyll absorbs maximally at 700 nm; PSII reaction center chlorophyll absorbs maximally at 680 nm.
The PSII reaction center is a multi-subunit protein–pigment complex (Figures 9.21, 9.22).
Manganese ions are required to oxidize water. Two hydrophobic plastoquinones accept electrons from PSII (Figures 9.19, 9.23).
Protons are transported into the thylakoid lumen when electrons pass through the cytochrome b6f complex (Figures 9.19, 9.25).
Plastoquinone and plastocyanin carry electrons between PSII and PSI (Figure 9.25).NADP+ is reduced by the PSI reaction center, using Fe–S centers and ferredoxin as electron carriers (Figure 9.26).
Herbicides may block photosynthetic electron flow (Figure 9.27).
Video Timestamps:
0:00 Introduction
0:49 Midpoint potential
Charge separated state, negative value in the Y axis of Z scheme, voltmeter
2:18 Pheophytin reduction
3:46 Strongest oxidizing agent
P680 and splitting of water
5:27 9.6 Midpoint potential
The concept of battery and voltage
7:16 Thylakoid membrane and integral proteins
7:43 Plastoquinone as an electron carrier
Not part of integral protein
9:20 Q Cycle
Involving plastoquinone and Cytochrome b6f, the result of electron transfer
10:18 Movement of the proton from stroma to lumen
Plastohydroquinone releases proton into the luminal side of the thylakoid membrane from the stroma
12:20 Production of ATP
PH imbalance between stroma and lumen side, ATP Synthase structure, equilibrium
14:48 Difference between NADPH and ATP
Where they are being used, phosphorylation
17:32 Proton motive force
What it is and different forms of hydrogen
18:30 Photo induces electronic components
Explaining charge separation state, how an electron can be ejected out, orbital
25:10 Recombination process
Electron does not proceed with the electron transport chain, wasteful
27:39 Absorption spectrum
Maximal absorption of light, different wavelength
28:30 Action spectrum
The result of the energy absorption
31:27 Two types of excited state
Lower excited state, higher excited state
32: 39 Sunscreen in plants
Different chlorophyll pigments, function
34:00 Inside the integral protein for PS II function
Multi-subunit pigment and protein complex
Diagram explanation
36:42 Antenna complex
37:04 Oxygen evolving complex
Splitting of water, dissolved oxygen
42:26 Hydrolysis
Splitting/oxidation of water, the pool of recycling
44:37 Detail explanation of the plastoquinone
How plastoquinone become plastohydroquinone
48:51 Cytochrome b6f
Structure of the cytochrome b6f, Qo, Qi, regular z scheme, Q cycle path (electron movement inside cytochrome b6f), free random plastoquinone, reobtaining plastoquinone after
55:53 Plastocyanin
Smallest and water-soluble protein, pass electron to P700 from the regular z scheme
56:51 Photosystem I
Excitation of P700, electron transfer, NADP reductase (FNR), production of NADPH
58:24 Iron sulphur protein
Importance of giving iron to the plants
58:47 Iron deficiency in plants
Electron transport chain cannot happen, reconstitution of the broken PS I chain
1:00:55 Iron sulphur centre
Three types of iron sulphur proteins
1:01:53 NADPH
Full name and pronunciation of NADP+ and NADPH, formation of NADPH
1:04:17 Knowledge utilization of the photosystem I & II
Herbicide production and mode of action
1:05:38 Paraquat
Interference of PS I using paraquat
1:07:16 Quizzes and exercise
1:09:04 First test
Keywords: photosynthesis, photosystem, chlorophyll, electron transport chain, Z scheme, Q cycle, ATP synthesis, light-dependent reactions, photophosphorylation, plastoquinone, cytochrome b6f, photosystem II (PSII), photosystem I (PSI), electron carriers, electron acceptors, light absorption, reaction center, thylakoid membrane, grana, stroma
Location
Faculty of Agriculture, Universiti Putra Malaysia
Fakulti Pertanian, Universiti Putra Malaysia, 43000 Seri Kembangan, Selangor
XPMM+9J Seri Kembangan, Selangor
2.9845517506267742, 101.73803356324866
Attribution 4.0 International — CC BY 4.0 - Creative Commons
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