energy. Thus it is called the reaction centre. Other pigments such as chlorophyll b and carotenoids are called accessory pigments as they pass on the absorbed energy to chlorophyll a (Chl.a) molecule. Reaction centre (Primary pigments) and harvesting centre (Accessary pigments) together form photo systems.
. . Role of Sunlight in Photosynthesis The entire process of photosynthesis takes place inside the chloroplast. The structure of chloroplast is such that the light dependent ( Light reaction ) and light independent ( Dark reaction ) take place at different sites in the organelle .
Light dependent Reaction (Hill reaction \ Light reaction) This was discovered by Robin Hill ( ). This reaction takes place in the presence of light energy in thylakoid membranes (grana) of the chloroplasts. Photosynthetic pigments absorb the light energy and convert it into chemical energy ATP and NADPH+H + . These products of light reaction move out from the thylakoid to the stroma of the chloroplast.
More to Know ATP Adenosine Tri Phosphate ADP Adenosine Di Phosphate NAD Nicotinamide Adenine Dinucleotide NADP Nicotinamide Adenine Dinucleotide Phosphate A cell cannot get its energy directly from glucose. So in respiration the energy released from glucose is used to make ATP (Adenosine Triphosphate) . Light independent reactions (Dark reaction) (Biosynthetic phase) Dark reaction or biosynthetic pathway is takes place in stroma . During this reaction CO is reduced into carbohydrates with the help of light generated ATP and NADPH+H + .
This is also called as Calvin cycle and is carried out in the absence of light. It is called dark reaction. In Calvin cycle the inputs are CO from the atmosphere and the ATP and NADPH+H + produced from light reaction. Figure .
Overview of Hill and Calvin cycle Melvin Calvin, an American biochemist, discovered chemical pathway for photosynthesis. The cycle is named as Calvin cycle. He was awarded with Nobel Prize in the year for his discovery. .
. Factors Affecting Photosynthesis a) Internal Factors : i) Pigments ii) Leaf age iii) Accumulation of carbohydrates iv) Hormones b) External Factors : i) Light