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Photosynthesis and some generally interesting facts about plants and whatnot Biophysical Seminar 2011. December 2. Bence Ferdinandy Physics MSc II.

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Presentation on theme: "Photosynthesis and some generally interesting facts about plants and whatnot Biophysical Seminar 2011. December 2. Bence Ferdinandy Physics MSc II."— Presentation transcript:

1 Photosynthesis and some generally interesting facts about plants and whatnot Biophysical Seminar December 2. Bence Ferdinandy Physics MSc II.

2 Bence Ferdinandy – Biophysics Seminar december 2. Introduction

3 Bence Ferdinandy – Biophysics Seminar december 2. Introduction Light phase binding of energy emission of oxigen Dark phase binding of CO 2 sugar synthesis

4 Bence Ferdinandy – Biophysics Seminar december 2. Outline of the talk The anatomy of Photosynthesis The Light phase The Dark phase Problems: photorespiration The efficiency of photosynthesis

5 Bence Ferdinandy – Biophysics Seminar december 2. The plant cell (EM pic)

6 Bence Ferdinandy – Biophysics Seminar december 2. The plant cell (cartoon)

7 Bence Ferdinandy – Biophysics Seminar december 2. Endosymbiothic theory Our ancestor protista ate bacteria like things: mithochondria and chloroplast Evidence: double membrane own DNA lot of things similar to bacteria they replicate separately (we get our mother’s) We are not alone in our own cells! Shocking piece of information

8 Bence Ferdinandy – Biophysics Seminar december 2.. Chloroplast (EM pic) M P Grana (thylakoid membrane) Lamella (thylakoid membrane)

9 Bence Ferdinandy – Biophysics Seminar december 2. Chloroplast (cartoon)

10 Bence Ferdinandy – Biophysics Seminar december 2. Purpose of the light phase: high energy molecules ATP: Adenosine triphosphate NADPH: Nicotinamide adenine dinucleotide phosphate Very important, (almost) everything works with it. Made in mitchondria also.

11 Bence Ferdinandy – Biophysics Seminar december 2. Light phase I. (the electron transportchain)

12 Bence Ferdinandy – Biophysics Seminar december 2. Light phase I. (the electron transportchain) „OUTSIDE” „INSIDE”

13 Bence Ferdinandy – Biophysics Seminar december 2. Light phase I. (the electron transportchain)

14 Bence Ferdinandy – Biophysics Seminar december 2. The heart of it all: the Photosystem What happens here?

15 Bence Ferdinandy – Biophysics Seminar december 2. Photosystem II Quite a beauty if ya ask me.

16 Bence Ferdinandy – Biophysics Seminar december 2. The light harvesting complex of the Photosystems The harvesting complex: Energy transfer with FRET Chlorophyll-A molecule Special pair

17 Bence Ferdinandy – Biophysics Seminar december 2. One photon excites one electron

18 Bence Ferdinandy – Biophysics Seminar december 2. The electron is passed to a plastoquinone One PQ can take two electrons

19 Bence Ferdinandy – Biophysics Seminar december 2. Plastoquinone takes up two protons from the stroma („outside”)

20 Bence Ferdinandy – Biophysics Seminar december 2. Plastoquinone gives the two electrons to cytochrome And the two protons to the lumen („inside”)

21 Bence Ferdinandy – Biophysics Seminar december 2. PSII lost two electrons: it splits water to get electrons, one H 2 O = e - 2 H 2 O = O p + -> more protons „inside” Risky!

22 Bence Ferdinandy – Biophysics Seminar december 2. Cytochrome transfers the two electrons to plastocyanin Two more protons are pumped to the lumen („inside”)

23 Bence Ferdinandy – Biophysics Seminar december 2. Plastocyanin takes the two electrons to PSI The electrons are now ground state: their energy lost in the transfer and proton pumping

24 Bence Ferdinandy – Biophysics Seminar december 2. Electrons are excited again and transfered to the the Ferredoxin NADP Reductase by ferredoxin

25 Bence Ferdinandy – Biophysics Seminar december 2. The FNR puts the energy of the electrons into NADPH

26 Bence Ferdinandy – Biophysics Seminar december 2. Now there’s a concentration gradient of protons, so the protons go back „outside” through the ATP synthase.

27 Bence Ferdinandy – Biophysics Seminar december 2. The energy of the gradient is stored in ATP. ATP synthase is like a turbine and is rotated by the proton flow.

28 Bence Ferdinandy – Biophysics Seminar december 2. Light phase II.

29 Bence Ferdinandy – Biophysics Seminar december 2.. Light phase III. 2 H 2 O, 4 photons 2 NADPH, 3 ATP, 1 O 2 12 protons pumped

30 Bence Ferdinandy – Biophysics Seminar december 2. Absortion spectrum of chlorophyll

31 Bence Ferdinandy – Biophysics Seminar december 2. Excitation levels of chlorophyll S0S0 S1S1 S2S2 S3S3 T1T1 light

32 Bence Ferdinandy – Biophysics Seminar december 2. Excitation levels of chlorophyll S0S0 S1S1 S2S2 S3S3 T1T1 light Fast energy loss photosynthesis

33 Bence Ferdinandy – Biophysics Seminar december 2. Excitation levels of chlorophyll S0S0 S1S1 S2S2 S3S3 T1T1 light Fast energy loss photosynthesis Fluorescence Phosphorescence

34 Bence Ferdinandy – Biophysics Seminar december 2. Dark phase I: RuBisCO Ribulose-1,5-bisphosphate carboxylase oxygenase: The most abundant protein on Earth.

35 Bence Ferdinandy – Biophysics Seminar december 2. Dark phase II: Calvin-cycle RuBisCO + 3 RuBP (5C) + 3 CO 2 3 pc. 6C 6 pc. 3PGA (3C) 13 steps, energy consuming process (Calvin cycle)  1 G3P (3C)  3 RuBp 2 G3P 1 glucose (6C) the energy used during this:  12 NADPH  18 ATP 24 photons

36 Bence Ferdinandy – Biophysics Seminar december 2. Calvin cycle

37 Bence Ferdinandy – Biophysics Seminar december 2. Photorespiration RuBisCO can take O 2 as substrate, creates useless product (concentration dependent) reversing the product needs energy, process loses C it is done by the photorespiration complex (chloroplast + mitochondrion + peroxisome) types of photosynthesis: C 3, C 4, CAM

38 Bence Ferdinandy – Biophysics Seminar december 2. C3 Photosynthesis Typical (85%) Just explained how it works Fixes CO 2 into C3 product Inefficient in hot and dry circumstances, because leaves „close” (don’t lose water, can’t take up CO 2

39 Bence Ferdinandy – Biophysics Seminar december 2. C4 Photosynthesis Spatial separation Fixes CO 2 in outer cell with PEP (another ensym) to C4 product C4 into CO 2 in inner cell Calvin cycle in inner cell RuBisCo doesn’t meet high concentration of oxygen Example: sugarcane, corn

40 Bence Ferdinandy – Biophysics Seminar december 2. CAM Photosynthesis Temporal separation, 1 cell Fixes CO 2 with PEP during night while Calvin cycle is not going Closes cell during day and does Calvin cycle Example: Cactus, pineapple

41 Bence Ferdinandy – Biophysics Seminar december 2. Efficiency I. Loses of energy during the whole process: ~30% - cross section ~47% - limited absorbtion range ~24% - uses energy of red quanta only ~68% - during the glucose production ~35-45% - photorespiration and such this estimate gives 5-6% efficiency

42 Bence Ferdinandy – Biophysics Seminar december 2. Efficiency II. Theoretical: 30% (including the energy loss of chemical reactions Laboratory conditions: 25% Natural conditions: in Death Valley (winter evening primrose): 8% sugarcane: 7% (remember, it’s C4) most crops: 1-4 % This 1-7% is also used to upkeeping, growing, reproduction

43 Bence Ferdinandy – Biophysics Seminar december 2. Efficiency III. Comparison with solar panels: theoretical: 86% laboratory: > 40 % commercial (cheap/not so cheap): ~6% / 15-20% BUT: the plant is a self-replicating, self-maintaining solar cell, and enviroment friendly (no rare elements needed)

44 Bence Ferdinandy – Biophysics Seminar december 2. What we have learned the anatomy of the photosynthetic apparatus: chloroplast light phase: electron transport chain, water splitting, O 2 making generates high energy molecules, uses proton gradient dark phase: CO 2 fixation with RuBisCO + energy = glucose photorespiration: RuBisCO can fix O 2 as well -> C3, C4, CAM paths efficiency: below 10%

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