Definition Photosynthesis: The synthesis of organic compounds like carbohydrates or glucose by the cells of green plants in presence of light of sunlight with help of Carbon dioxide and Water is called photosynthesis.
During this process the radiant energy of sunlight is stored in carbohydrates. Because the carbon of used Carbon dioxide (CO2) in this process is assimilated, it is also called carbon assimilation process. The mechanism of photosynthesis can be represented by the following simple equation:
Ruben and Kamen (1941) demonstrated that the evolution of O2 in this process takes place by the oxidation or dissociation of water molecules. Therefore, the above equation can be correctly written as:
Certain micro organisms like bacteria during photosynthesis are able to reduce Carbon dioxide(CO2) into essential organic constituents in presence of light using H2S, hydrogen and other inorganic and organic redunctants instead of water. In such bacterial photosynthesis O2 evolved and the bacteria inhabitant anaerobic environment. Such bacteria are called photosynthetic bacteria and photosynthesis as bacterial photosynthesis.
Plant Photosynthesis vs Bacterial Photosynthesis
1. Plants contain definite chloroplasts
2. In plants photosynthesis, the pigments involved are chlorophylls, caretonoids and phycobilins
3. It takes place at wavelengths between 400 to 700 mμ
4. The CO2 reductants is NADPH + H+
5. The electron donor in this is only H2O
6. Oxygen is evolved
7. Two pigment systems are involved
8. The reaction centre of PS I is P700 and of PS II is P673 or P680
9. Non cyclic photophosphorylation is dominant
10. Emerson’ s enhancement effect occurs.
1. Bacteria lack definite chloroplasts
2. In bacterial photosynthesis, the pigments involved are bacterio-chlorophylls, bacterioviridin and open chain aliphatic carotenoids.
3. It takes place at wavelengths above 700 mμ
4. The reductants is NADH + H+
5. The electron donors in this are H2S, inorganic compounds and reduced organic compounds
6. Oxygen is not evolved
7. It involves only one pigment system
8. The reaction centre is only P890
9. Cyclic photophosphorylation is dominant
10. Emerson’ s enhancement effect occurs is not reported.