Photosynthesis in Higher Plants

Introduction

Photosynthesis in higher plants is a physicochemical process. It is a cycle where different processes are involved. The normal photosynthesis cycle consists of the process of organic compounds being synthesised in the presence of sunlight. The organic compounds synthesised in the presence of light energy are sugar. Oxygen is released into the atmosphere during the process of photosynthesis.

Today, in this article, we will be talking about photosynthesis in higher plants, actions in the photochemical phase, and steps involved in photosynthesis. 

Photosynthesis In Higher Plants:

Photosynthesis is the primary source of food, where light energy is transformed into chemical energy. During photosynthesis, green plants capture light energy and use it to convert water, carbon dioxide, and minerals. These components are converted into oxygen and organic compounds. Organic compounds are sugar and energy-rich in nature. Chlorophyll, the green pigment, is essential for the process of photosynthesis. 

In the Photochemical phase, the following actions take place:

  • Light absorption: Chlorophyll absorbs violet-blue and reddish-orange wavelengths of visible light, except for green colour. The green pigment reflects the green and yellow-green wavelengths
  • Water splitting: Water is broken down into oxygen and hydrogen in the chloroplast in a chemical reaction. Light energy remains absorbed by chlorophyll
  • Releasing of Oxygen: From the water, oxygen is released. Water and carbon dioxide are absorbed during photosynthesis. The water molecules slowly get converted into oxygen and sugar. Sugar molecules provide energy, whereas oxygen gets released into the atmosphere
  • ATP and NADPH: The light energy gets converted into chemical energy. In plants, hydrogen is bonded to NADP, which produces NADPH, which generates ATP. A proton is connected to the coenzyme NADP, which becomes NADPH, an energy currency for plants

Steps Involved In Photosynthesis:

  • Carbon dioxide and water enter the leaf to initiate the process of photosynthesis
  • Sunlight hits the green colour pigment, chlorophyll, present in the thylakoid membrane. Thylakoids are membrane compartments present inside the chloroplasts. They are essential for light-dependent reactions during the process of photosynthesis
  • The splitting of H2O into O2 takes place in the thylakoid
  • The electrons move down through the proteins present in the thylakoid membrane to enzymes
  • The light-dependent reaction takes place, where sunlight hits the second pigment molecule. This allows the conversion of ADP to ATP and NADP+ to NADPH. These are energy sources or high-energy chemical intermediates in photosynthesis. NADPH assists as they are primarily electron donors. ADP and NADP+ travel back to the thylakoid membrane to restore that membrane to take part in the light-dependent reaction
  • ATP and NADPH are used as power sources. They facilitate the conversion of carbon dioxide into simple organic compounds (sugar glucose)
  • In the Calvin cycle, three CO2 molecules present in the atmosphere are converted to organic compounds
  • Following the light reaction, CO2 present in the atmosphere is fixed and reduced into carbohydrates

Calvin Cycle:

Calvin cycles take advantage of carbon dioxide in the air to make sugar and the food autotrophs need to grow. Plants use the Calvin cycle to create three-carbon sugars. These three-carbon sugars can be utilised to develop other sugars like glucose, starch, and cellulose for structural purposes. The Calvin cycle takes carbon atoms straight from the atmosphere and turns them into plant matter (RuBP). 

The Calvin cycle uses carbon dioxide (from the atmosphere) to add carbon to a simple five-carbon molecule. A chemical reaction occurs in which NADPH and ATP are converted into glucose through the Calvin cycle, using NADPH and ATP from the light reactions as energy. 

The Calvin cycle process can be explained in the following three stages: carboxylation, reduction, and regeneration.

  1. Carboxylation: Carboxylation occurs in the presence of RuBP carboxylase (RuBisCO), resulting in two molecules of 3-PGA. Carboxylation of RuBP occurs in the presence of RuBP carboxylase (RuBisCO).
  2. Reduction: The reduction of glucose is a series of reactions involving ATP and NADPH. Six turns of the cycle must occur for one glucose molecule to be removed from the pathway. 
  3. Regeneration: The regeneration process requires one molecule of ATP. It is done by generating RuBP molecules for the continuation of the cycle.

Conclusion: 

The synthesis of organic compounds in plants is driven by a physical-chemical process known as photosynthesis. Photosynthesis in Higher plants study material will enhance your knowledge and develop your learning to conclude that plant pigments are primarily involved in photosynthesis. These pigments involve the green pigment chlorophyll and many other colour pigments that absorb as much light energy as possible. Violet and blue wavelengths in the visible spectrum of solar radiation are absorbed mainly by the carotenoids of higher plants. The wavelengths of blue light are more energetic than those of red light.

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