1. LB145 F11 Thursday September 29, 2011 Class Outline
Photosynthesis
A Carrot (Eyes on the Prize)
Capturing Light
Using Light Energy to Do Work!

2. Evidence Supporting Endosymbiont Origin of Mitochondria and Chloroplasts
Chloroplast ribosomes are very similar to eubacterial ribosomes
Chloroplast DNA sequences come out with bacterial DNA sequences in molecular phylogenies

3. Ancestral photosynthetic Endoplasmic reticulum
eukaryote
Photosynthetic
prokaryote
Mitochondrion
Plastid
Nucleus
Cytoplasm
DNA
Plasma membrane
Endoplasmic reticulum
Nuclear envelope
Ancestral
Aerobic
heterotrophic
Model for Serial Endosymbiosis and the Origin of Eukaryotes
Campbell 8e, Fig. 25.9

5. Photosynthesis – Minute Paper (worth 1 point)
What is the relationship of the light and dark reactions of photosynthesis? In other words, what things are produced in each set of reactions, and how does one set of reactions depend on the other?

6. Photosynthesis – Connect the two halves!!!
Light
Campbell 8e, Fig
H2O
Chloroplast
Reactions
NADP+ P
ADP i +
ATP
NADPH O2
Calvin
Cycle
CO2
[CH2O]
(sugar)

7. Photosynthesis – Minute Paper (Pt. 2) (worth 1 more point)
What is the relationship of the light and dark reactions of photosynthesis? In other words, what things are produced in each set of reactions, and how does one set of reactions depend on the other?
How does a root cell, in a photosynthetic plant like a carrot, obtain food? How do these root cells use this food?

8. Photosynthesis
How does a cell at the growing point of a plant root get the energy it needs to grow and divide?

9. Change the scale of your thinking!
Organelle-level

10. Photosynthetic Leaf Section
Organ-level
Key
to labels
Dermal
Ground
Vascular
Cuticle
Sclerenchyma
fibers
Stoma
Bundle-
sheath
cell
Xylem
Phloem
(a) Cutaway drawing of leaf tissues
Guard
cells
Vein
Lower
epidermis
Spongy
mesophyll
Palisade
Upper
Stomatal
pore
Surface view of a spiderwort
(Tradescantia) leaf (LM)
Epidermal
(b)
50 µm
100 µm
Air spaces
Guard cells
Cross section of a lilac
(Syringa)) leaf (LM)
(c)
Campbell 8e, Fig

11. Plants make sugar in their leaves
How does a cell at the growing point of a plant root get the energy it needs to grow and divide?

12. Vascular Bundles
Phloem - All plant tissues need sugars made in photosynthetic tissue
Xylem - Stems and leaves need water and minerals from the roots

13. Sucrose from the leaves is shipped to the roots!
Phloem - sugar transport
There is phloem in the leaves
There is phloem in the stems
There is phloem in the roots

14. Think about the plant as a whole organism!
Where does it get made?
Where does it get used?
How does it get there?

15. Sucrose Transport (in plant vascular tissue)
Source cell (leaf)
Vessel (xylem)
Sieve tube (phloem) 1
Loading of sugar
Sucrose Transport (in plant vascular tissue)
H2O 1
Sucrose
H2O 2 2
Uptake of water
Bulk flow by positive pressure
Bulk flow by negative pressure 3
Unloading of sugar
Sink cell (storage root) 4
Water recycled 4 3
Sucrose
H2O
Fig

16. Sieve Tubes Sieve-tube elements: longitudinal view (LM) 3 µm
Sieve plate
Sieve-tube element (left)
and companion cell:
cross section (TEM)
Companion
cells
Sieve-tube
elements
Plasmodesma
Sieve
plate
30 µm
10 µm
Nucleus of
companion
cells
Fig e
Sieve-tube elements:
longitudinal view
Sieve plate with pores (SEM)

17. Sucrose Loading (there’s your co-transporter, in action!)
High H+ concentration
Cotransporter
Mesophyll cell
Proton pump
Cell walls (apoplast)
Companion (transfer) cell
Sieve-tube element H+ S
Plasma membrane
Plasmodesmata
Key
ATP
Apoplast
Sucrose H+ H+
Bundle- sheath cell
Phloem parenchyma cell S
Symplast
Low H+ concentration
Mesophyll cell
Fig

18. Why sucrose?

19. Why sucrose?
ATP is a lousy transport form of energy!

20. Why sucrose? ATP is a lousy transport form of energy!
ATP is a lousy storage form of energy!

21. Chloroplasts are not the only plastids!

22. How did Engelmann figure this out?
Campbell 8e, Fig. 10.9

23. Photosynthetic Pigments

24. Photosynthetic pigments are arranged in an array
Photosynthetic Antennal Complex
Photosynthetic pigments are arranged in an array

25. Change the scale of your thinking!
Organelle-level

26. Chlorophyll molecules transmit energy from excited electrons in the antenna complex to a reaction center

27. Photosystem Football Antennal Complex – C106 chairs and tables
Reaction Center – Front Row Team
Primary Electron Acceptor – Help me out!
A Photon of Light – The Football

28. Photosynthesis Movie

29. PHOTOSYSTEM II (Feb 2004)
Photosynthesis uses light energy to drive the oxidation of water at an oxygen-evolving catalytic site within photosystem II (PSII). We report the structure of PSII of the cyanobacterium Thermosynechococcus elongatus at 3.5 Å resolution. We have assigned most of the amino acid residues of this 650 kDa dimeric multisubunit complex and refined the structure to reveal its molecular architecture. Consequently we are able to describe details of the binding sites for cofactors and propose a structure of the oxygen-evolving center (OEC). The data strongly suggest that the OEC contains a cubane-like Mn3CaO4 cluster linked to a fourth Mn by a mono-µ-oxo bridge. The details of the surrounding coordination sphere of the metal cluster and the implications for a possible oxygen-evolving mechanism are discussed.
Kristina N. Ferreira, Tina M. Iverson, Karim Maghlaoui, James Barber, and So Iwata (2004) Architecture of the Photosynthetic Oxygen-Evolving Center Science [DOI: /science ]

30. What is the error (or forced misconception) in this diagram?
The Z-Scheme
What is the error (or forced misconception) in this diagram?

31. Photosynthesis Movie

32. What is the error (or forced misconception) in this diagram?
The Z-Scheme
What is the error (or forced misconception) in this diagram?

33. What is the error (or forced misconception) in this diagram?
The Z-Scheme
What is the error (or forced misconception) in this diagram?

34. (low H+ concentration) (high H+ concentration) (low H+ concentration)
Chloroplast Electron Transport Chain – DOES NOT Yield ATP Directly!!!
STROMA
(low H+ concentration)
Cytochrome
complex
Photosystem II
Photosystem I
4 H+
Light
NADP+
reductase
Light Fd 3
NADP+ + H+ Pq
NADPH e– Pc e– 2
H2O 1
1/2 O2
THYLAKOID SPACE
(high H+ concentration)
+2 H+
4 H+ To
Calvin
Cycle
Thylakoid
membrane
ATP
synthase
STROMA
(low H+ concentration)
ADP +
ATP P i H+
Campbell 8e, Fig

35. (low H+ concentration) (high H+ concentration) (low H+ concentration)
Chloroplast Electron Transport Chain:
Where does ATP synthesis take place (and why)?
STROMA
(low H+ concentration)
Cytochrome
complex
Photosystem II
Photosystem I
4 H+
Light
NADP+
reductase
Light Fd 3
NADP+ + H+ Pq
NADPH e– Pc e– 2
H2O 1
1/2 O2
THYLAKOID SPACE
(high H+ concentration)
+2 H+
4 H+ To
Calvin
Cycle
Thylakoid
membrane
ATP
synthase
STROMA
(low H+ concentration)
ADP +
ATP P i H+
Campbell 8e, Fig