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

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

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

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?

Photosynthesis – Connect the two halves!!! Light Campbell 8e, Fig. 10-5-4 H2O Chloroplast Reactions NADP+ P ADP i + ATP NADPH O2 Calvin Cycle CO2 [CH2O] (sugar)

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?

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

Change the scale of your thinking! Organelle-level

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. 35-18

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?

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

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

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

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. 36-20

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. 35-10e Sieve-tube elements: longitudinal view Sieve plate with pores (SEM)

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. 36-19

Why sucrose?

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

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

Chloroplasts are not the only plastids!

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

Photosynthetic Pigments

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

Change the scale of your thinking! Organelle-level

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

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

Photosynthesis Movie http://35.9.122.184/Photosynthesis.mov

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: 10.1126/science.1093087]

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

Photosynthesis Movie http://35.9.122.184/Photosynthesis.mov

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

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

(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. 10-17

(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. 10-17