Similarities between photophosphorylation and oxidative phosphorylation

e-

Proton pump

ATP synthase

H+

H+ H+ H+ H+

H+

H+

ADP+Pi

ATP

Differences between photophosphorylation and oxidative phosphorylation

e-Proton pump

ATP synthase

H+

H+ H+ H+ H+ H+

H+ADP+Pi

ATP

NADHFADH2

NADP+

NADPH

O2

H2O

p723

Photosynthesis:The light reactions

(photophosphorylation)

Chlorophyll (or other pigments) absorbs light energy and conserve it as ATP and NADPH.Not all photosynthetic organisms use H2O as electron donor in photosynthesis; thus not all of them produce O2 while they produce ATP and NADPH.There are two types of photosynthesis: oxygenic (producing oxygen) photosynthesis and anoxygenic (not producing oxygen) photosynthesis. Only organisms with two photosystems can do oxygenic photosynthesis.At lease half of the photosynthsis in this world is done by microorganisms (algae, photosynthetic eukaryotes and photosynthetic bacteria).

p724

Outer membraneInner membrane

Thylakoid membrane(lamellae)

grana

stroma

lumen

p729

Chloroplast has photosystems with closely arranged chlorophyll

p727

Cyanobacteria & red algae also contain similar structures called phycobilisome to facilitate light absorption

p726

Alternating single and double bonds give strong absorption in the visible light

The major light absorbing pigment in higher plants

p726

The accessory pigment in bacteria and algae

p725

The spectrum of electromagnetic radiation

p727

Chlorophylls can cover part of the spectrum – blue and red

The part of spectrum covered by chlorophylls coincides with the action spectrum of photosynthesis

Accessory pigment: the red-orange -carotene

p726

Accessory pigment: lutein (the red-orange isoprenoid)

-carotene and lutein can help plant absorb more light

Phycoerythrin and phycocyanin can absorb light that other pigments cannot absorb

p731(PSII) (PSI)

Anoxygenic photosynthesis

(pheophytin)

(ferredoxin)

(restore RC to original state)

(restore RC to original state)

p733

The Z scheme of oxygenic photosynthesis

Purple bacteria type

Green bacteria type

(pheophytin)

(plastoquinone)

(A1)

p736

LHCII holds grana together

PSI and PSII on thylakoid membrane are separated to prevent Excition Larceny

Granal stacking by LHCII is regulated by light intensity

p737

Cytochrome b6f complex

p738

Oxidative phosphorylation and photophosphorylation has something in common in cyanobacteria

p739

Oxygen-evolving complex(water-splitting complex)

can only accept one electron at a timeIn protein subunit D1 of the PSII reaction center; the immediate electron donor to P680

Loses one electron and proton at a time to P680; electrically neutral Tyr free radical (Tyr•) is generated

tyr• then regain its electron and proton by oxidizing four Mn in the water splitting complex; each transfer corresponds to one photon absorption

Here the Mn complex takes four electrons from a pair of water molecules; releasing 4H+ and O2

Goes to lumen

p741

P

N

p742

N

N

N

p744

bacteriorhodopsin

All-trans-retinal 13-cis-retinol

Proton transport

p1062

Chloroplast from higher plants is probably evolved from endosymbiotic bacteria (prochlorophytes)Chloroplast from red algae is probably evolved from cyanobacteria