Saran's Learn Microbiology

PHOTOSYNTHESIS REACTIONS Photosynthesis takes place in two stages. In the First stage, called the Light reactions, the light energy is used to convert ADP and Phosphates to ATP. In addition, in the predominant form of the light-dependent reactions, the electron carrier NADP + is reduced to NADPH. The coenzyme NADPH, like NADH, is an energy- rich carrier of electrons. In the Second stage, the light-independent (Dark) reactions, these electrons are used along with energy from ATP to reduce CO 2 to Carbohydrate sugar. LIGHT REACTION (or) LIGHT DEPENDENT REACTION (or) PHOTOPHOSPHORYLATION Photophosphorylation is one of the three ways ATP is formed, and it occurs only in photosynthetic cells. In this mechanism, Light energy is absorbed by Chlorophyll molecules in the photosynthetic cell, exciting some of the molecules electrons. The Chlorophyll is located in the membranous Thylakoids of Chloroplasts in Algae and Green plants. In Cyanobacteria, Thylakoids are found in the photosynthetic

  Difference between Plant, Algal and Bacterial Photosynthesis Features Plant & Algal Photosynthesis Bacterial Photosynthesis Organisms Plant, Algae & Cyanobacteria Purple bacteria & Green bacteria Oxygen production Oxygenic and Aerobic Anoxygenic and Anaerobic Photosynthetic pigments Chlorophylls, Carotenoids and Phycobilins (400 to 600 nm) Bacteriochlorophyll, Bacterioviridin and Open chain aliphatic Carotenoids (above 700 nm) Types of Chlorophyll Chlorophyll – a and Chlorophyll – c (only in certain Marine algae) Bacteriochlorophyll – a (Green bacteria) & Bacteriochlorophyll – a or b (Purple bacteria) Site of Photosynthesis Chloroplast with Thylakoids (Plants & Algae) and Thylakoids (Cyanobacteria) Chromosomes (Green bacteria) and Chromatophores (Purple bacteria)

  PHOTOSYNTHESIS IN MICROORGANISMS AND PHOTOSYNTHETIC PIGMENTS The process by which light energy is trapped and converted to chemical energy is called Photosynthesis. Microorganisms derive energy not only from the oxidation of inorganic and organic compounds but also from light energy, which they capture and use to synthesize ATP and reduce power (e.g., NADPH). Essentially, photosynthesis is the conversion of light energy from the sun into chemical energy. The chemical energy is then used to convert CO 2 from the atmosphere to more reduced carbon compounds, primarily sugars. This synthesis of sugars by using carbon atoms from CO 2 gas is also called Carbon fixation. In Prokaryotes, Photosynthesis takes place in the Plasma membrane. In Eukaryotes, Photosynthesis takes place in the Chloroplast. DIVERSITY OF PHOTOSYNTHETIC ORGANISMS Eukaryotic organism - a)  Plant; b) Multicellular Algae (Green algae, Red algae, and Brown algae), and c) Unicellular Protists (Euglenoids, Dinoflagellate