Question

What is dark reaction and light reaction

Answer 1

Dark Reaction : the cycle of reactions (the Calvin cycle) which occurs in the second phase of photosynthesis and does not require the presence of light. It involves the fixation of carbon dioxide and its reduction to carbohydrate and the dissociation of water, using chemical energy stored in ATP.

Light Reaction :the reaction which occurs as the first phase of photosynthesis, in which energy in the form of light is absorbed and converted to chemical energy in the form of ATP.

Answer 2

Hey !!

DARK REACTION

• Dark reaction of photosynthesis occurs in stroma(matrix) part of chloroplast.
• It is also known as Calvin cycle or C₃ cycle.
• In this cycle one mole of hexose sugar (glucose) is formed by 18 ATP + 12 NADPH₂. This process of CO₂-fixation occurs in the presence of RuBisCO enzyme (most abundant enzyme).
• In some plants instead of C₃ cycle, C₄ cycle is observed. In this cycle, first stable product of CO₂-fixation is a four carbon compound unlike C₃ plants in which it is a 3 carbon compounds.
• This 4C compound produced in C₄ cycle is
• Oxaloacetic Acid(OAA). Which is the first product of Hatch and Sla.k pathway,
• In C₄ plants a special type of leaf anatomy, Kranz anatomy is seen.
• Example:- C₄ plant that are monocots are sugarcane, maize, Cyprus and dicots are Amaranthus, Artiplex can show both C₃ and C₄ cycle.
• In plants such as Opunita, Bryophyllum, Agave, etc. CO₂-fixation occurs at night. These plants are known as CAM plants and this process is known as Crassulaceae Acid Metabolism (CAM).          

LIGHT REACTION

• Light reaction of photosynthesis occurs in grana part of chloroplast. It involves photolysis of water and production of NADPH and ATP in photophosphorylation (production of ATP in the presence of light).
• Rate of photosynthesis is measured in quantum.
• Quantum requirement in photosystems involve in the process of light reaction.
• 1. P₇₀₀ is the reaction of PS-I
• 2. p₆₈₀₋ ₆₉₀ is the reaction centre of PS-II

GOOD LUCK !!