Photosynthesis is divided in two parts: 1. Light-dependent reactions (light reactions) 2. Light-independent reactions (dark reactions). Light reactions need light to produce organic energy molecules (ATP and NADPH). They are initiated by colored pigments, mainly green colored chlorophylls. Dark reactions make use of these organic energy molecules (ATP and NADPH). This reaction cycle is also called Calvin Benison Cycle, and it occurs in the stroma. ATP provides the energy, while NADPH provides the electrons required to fix the CO2(carbon dioxide) into carbohydrates. NOTES This means Dark reactions will fail to continue if the plants are deprived of light for too long, since they use the output of the initial light-dependent reactions Mechanism of Photosynthesis : (i) Light reaction : • It is also called as photochemical process. • It was discovered by ® ‘Robert Hill’ therefore it is also called as Hill’s reaction/ •Site : Grana of chloroplast. • Raw materials : Light and water. • Regulation : This process is regulated by chlorophyll molecules. • It consist of 3 steps : (A) Photo excitation of chlorophyll molecule : During this process chlorophyll molecule receives sunlight in the form of small energy bundles called as photons and become excited to higher energy level. (B) Photolysis : It is also called as photoxidation of water, this takes place in presence of Mn+2 and Cl- ions. 2H2O ------> 4H+ + O2 + 4e- O2 is liberated as by product and H+ ions are used for reduction of NADP 2NADP + 4H+ ------> 2NADPH2 (C) Photophosphorylation : During this process ATP are produced. It takes place in quantasomes. Mg+2 ions and inorganic phosphate is required to convert ADP ------> ATP, ADP + iP ----------------> ATP. (ii) Dark reaction : • It is also called as thermo chemical reaction. • It was discovered by Melvin calving and benson therefore it is also called as Calving cycle Site = Stroma of chloroplast. • Raw materials : They require CO2, NADPH2, ATP and Enzymes. • Regulated by : Light reaction and enzymes. • It involves three basic steps : (A) Carboxylation : In this step CO2 is captured by CO2 acceptors like RUBP (C3 Plants) PET (C4Plants) with the help of carboxylase enzyme i.e. RUBISCO & PEPCO respectively. (B) Synthesis : This phase cap true CO2 is assimilated into glucose in the presence of phosphatase and isomerease enzymes and RUBP is regenerated back (C) Regeneration of RUBP What is the importance of the light and dark reactions in photosynthesis? These two reactions are working simultaneously. The light reaction uses the solar energy from the sunlight and other sources to form ATP. This is a complete light-dependence reaction. Unlike this, the dark reaction can take place at night time. Because it transform ATP and other sources into glucose , it has to work together with the light reaction as well. What happens to food energy during photosynthesis? During cellular respiration? There’s no food energy during photosynthesis except solar energy. Photosynthesis provides food energy to animals which have respiration. Animals have to intake food energy glucose in order to produce energy themselves. Why is photosynthesis important to you? It’s important to us because we are taking the food energy from plants since we do not produce anything our own. What are the processes in cellular respiration? The first process will be Glycolosis, this step form pyruvic acid and two ATP by the break down of glucose and oxygen. The next step Why are photosynthesis and cellular respiration viewed as complementary processes? They are complementary because they when animals go through cellular respiration, we excrete carbon dioxide as our waste. However, the plant uses the co2 in the photosynthesis to produce glucose, which is essential for us. Describe the similarities and differences between photosynthesis and cell respiration. Plants and animals all use photosynthesis and cellular respiration in order to make themselves survive. They are produce some sort of energy for themselves. Eg. Glucose and ATP Searches related to what is the importance of the light and dark reactions in photosynthesis
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Electrical conductance measures how easily electricity flows along a certain path through an electrical element. The SI derived unit of conductance is the siemens. Because it is the reciprocal of electrical resistance (measured in ohms), historically, this unit was referred to as the mho. Oliver Heaviside coined the term conductivity in September 1885. Conductance is reciprocal to resistance. If R is the resistance of a component or device (in ohms), then the conductance G (in siemens) is given by: G = 1/R More Study: View Me |