Process involved in Bacterial photosynthesis.pptx

Photosynthesis
Mechanism
Significance

1. Metabolism-I Bacterial Photosynthesis

2. CONTENTS Introduction Photosynthetic Pigments Phases of Photosynthesis Types of Photosynthesis Oxygenic Photosynthesis Anoxygenic Photosynthesis Calvin Cycle References

3. INTRODUCTION Photosynthesis is a light-dependent reaction that occurs in autotrophic organisms where light energy is converted to chemical energy and the carbohydrate formed is stored as food. Photosynthesis is carried out by plants, blue-green algae (Cyanobacteria), and some bacteria such as purple and green-sulphur bacteria. The photosynthesis process in bacteria and plants differs. Bacterial photosynthesis is primarily an anoxygenic process in which O2 is not evolved (except in cyanobacteria), whereas plant photosynthesis is an oxygenic process in which O2 is evolved. There are two primary forms of bacterial photosynthesis: oxygenic and anoxygenic photosynthesis.

4. Photosynthetic Pigments Chlorophyll Chlorophyll is the photosynthetic pigment in all oxygenic bacteria called Cyanobacteria Contains a Magnesium atom in the center of the porphyrin ring Types of Chlorophyll : Chlorophyll a : Absorbs red light around 680 nm and is found in Cyanobacteria Chlorophyll b : Absorbs red light around 660 nm and is found in Prochlorophytes. Chlorophyll c : Absorbs red light between 450nm and 640nm and is found in eukaryotic microbes Chlorophyll d : It is found in a type of cyanobacterium that lives in areas lacking visible light, but containing infrared radiation. Bacteriochlorophyll Bacteriochlorophyll is found in anoxygenic phototrophic bacteria such as Purple bacteria, Purple-Sulphur bacteria, Purple Non-Sulphur bacteria and Green bacteria It absorbs light of red and blue region in the VIBGYOR. Types of Bacteriochlorophyll: Bacteriochlorophyll a and b : Absorbs infrared radiation (800nmto 1040nm) and are found in Purple bacteria. Bacteriochlorophyll c,d and e : Absorbs far red light (720nm to 750nm) and are found in Green Sulphur bacteria. Bacteriochlorophyll c s : Absorbs far red light (720nm) and is found in Green Non-Sulphur bacteria. Bacteriochlorophyll g : Absorbs red or far red light (670nmto 788nm) and is found in the Heliobacteria

5. Accessory Pigments Carotenoids They are hydrophobic pigments , firmly or tightly embedded in the membrane . May be yellow, red, brown or green in color. They protect the photosynthetic pigments from the destructive photooxidation that occurs in the presence of light and carbon-dioxide . Example : Chlorobactene, Rhodopsin, Lycopene Phycobiliproteins They are principle light harvesting pigments and are red or blue in color. The red pigment is called phycoerythrin and captures light at 550nm. The blue pigment is called phycocyanin and captures light at 620nm. Allophycocyanin absorbs light at about 650nm. Phycobiliproteins aggregate in the form of phycobilisomes .

6. Phases of Photosynthesis Cyanobacteria Thylakoid membrane located within the cell’s cytoplasm Anoxygenic bacteria Invaginations or infoldings of the cell membrane The two phases of photosynthesis are: Light Phase or Light reaction or Photophosphorylation: Light energy Chemical energy (ATP) NADP NADPH Dark Phase or Fixation or Assimilation of Carbon-dioxide in microorganisms : CO₂ Carbohydrates

7. TYPES OF PHOTOSYNTHESIS OXYGENIC PHOTOSYNTHESIS It is seen in Cyanobacteria. Chlorophyll is the photosynthetic pigment. Contain two distinct, interconnected photosystems : Photosystem I (P700) and Photosystem II (P680). The compounds used to carry electrons include pheophytin (Chlorophyll with Mg 2+ ion in the center), quinones, cytochromes, plastoquinones , non-heme Fe-S proteins, ferredoxin and flavoproteins. Two types of Photophosphorylation occurs in Cyanobacteria: Cyclic and Non-Cyclic Photophosphorylation

8. ANOXYGENIC PHOTOSYNTHESIS Example: Purple and Green Bacteria. Bacteriochlorophyll is the photosynthetic pigment They lack Photosystem II , hence, cannot use water as an electron donor and cannot produce oxygen as a byproduct.

9. REFERENCES Stanier, Y., Doudoroff , M., & Adelberg , E. A. (1958). General microbiology.  Vermaas , W. F. (2001). Photosynthesis and respiration in cyanobacteria.  e LS . Willey, J. M., Sherwood, L. M., & Woolverton, C. J. (2014).  Prescott's microbiology . McGraw-Hill. Lodish , H.F. (2003). Molecular cell biology 5 th edition, 331-344

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