Phototrophs Photophosphorylation for ATP generation: still requires a PMF and ATP synthase, light as an energy input instead of NADH (or reduced inorganic compound) oxidation. Photosynthesis (photoautotrophs): Light Reactions Cyclic Photophosphorylation (Photosystem I = PSI) Non-Cyclic Photophosphorylation (Photosystem II = PSII) Dark Reactions (Calvin Cycle) Photopigments: Chlorophylls; carotenoids; phycobiliproteins Antenna (hundreds of pigment molecules to capture light) Reaction-center chlorophyll (the link to electron transport)

Chlorophylls Cyanobacteria and Eukaryotes have Chlorophyll a Green and Purple Bacteria have Bacteriochlorophylls The core is a tetrapyrole ring with a magnesium molecule.

Prochloron and eukaryotes Accessory Pigments Prochloron and eukaryotes Eukaryotes alone Bind with proteins; cyanobacteria & red algae

Different phototrophs have different pigments. Pigments absorb light at unique wavelengths. Wavelengths of light reaching an environment can be different. Phototrophs best equipped to absorb available wavelengths in a given environment yield more energy.

Cyclic Photophosphorylation (PS I) Absorbs wavelengths ≥680 nm (P700)

Non-Cyclic Phosphorylation (PSII) Absorbs wavelengths ≤680 nm (P680)

Z-scheme NADP+

Green Sulfur Bacteria, Chlorobium Live in anoxic sulfide rich habitats. Sº accumulates outside the cell. Cyclic for ATP or non-cyclic to reduce NAD+.

Green Non-Sulfur Bacteria Thermophilic using organic matter for electron donor in photoheterotrphy; H2 for photoautotrophy (e.g. Chloroflexus).

Purple Sulfur Bacteria Live in sulfide rich and anoxic habitats. Anoxygenic photoautotroph. So accumulates intracellularly as inclusion bodies.

Purple Non-Sulfur, Rhodobacter Winogradsky column Need a supply of organics or H2. Tolerates O2 or S-2. Some photoautotrophs.

Phototrophy Overview Purple and Purple Non-Sulfur Bacteria require means of producing reduced electron carriers; done by reverse electron flow, as with chemolithoautotrophs. (or PMF)

Calvin Cycle Carboxylation Phase Ribulose 1,5-bisphosphate Fixation of 3 Carbon Dioxide molecules to one molecule of Glyceraldehyde 3-Phosphate (G3P) via carboxylation & reduction requires 3 cycles. Each cycle requires regeneration of Ribulose 1,5-bisphosphate (RuBP) to fix the next CO2 via the enzyme RuBP Carboxylase. Regeneration of RuBP from 5 G3Ps follows a reversal of the PPP. 6 cycles will yield 2 G3Ps, which can form a hexose via Gluconeogenesis. Regeneration Phase Reduction Phase

Anabolism

Nutritional Types Revisited