Mechanism of Photosynthesis

Using sunlight to synthesise nutrients from carbon dioxide and water, green plants and some other organisms use photosynthesis to achieve their nutritional goals. Photosynthesis in plants is generally characterised by the presence of the green pigment chlorophyll and the production of oxygen as a by-product.

In cells, the photosynthesis process takes place in organelles known as chloroplasts, which are responsible for the production of oxygen. In these organelles, there is a green-colored pigment known as chlorophyll, which is responsible for the distinctive green coloration of the leaves.

In addition to the fact that photosynthesis occurs in the leaves, it is also important to note that the chloroplast is the specialised cell organelle responsible for this process. A leaf is composed of three structural components: a petiole, an epidermis, and a lamina. During photosynthesis, the lamina is responsible for the absorption of solar radiation and carbon dioxide.

Steps of Photosynthesis

Carbon dioxide enters the plant through the stomata, and water is absorbed by the root hairs from the soil and transported to the leaves through the xylem vessels. Photosynthesis is a complex process that involves many steps. In order to split water molecules into hydrogen and oxygen, chlorophyll absorbs solar energy and converts it to chemical energy.

It is necessary to use hydrogen derived from water molecules as well as carbon dioxide absorbed from the atmosphere in order to produce glucose. Furthermore, as a waste product, oxygen is released into the atmosphere through the leaves of the plant.

A source of food for plants, glucose serves to fuel their growth and development while the remainder is stored in the roots, leaves, and fruits for use at a later time.

In addition to pigments, photosynthesis requires a number of other cellular components. They are the molecules that give colour to things, and they absorb light at a specific wavelength and reflect back the light that has not been absorbed. Chlorophyll a, chlorophyll b, and carotenoids are the primary pigments found in all green plants, and they are found in the thylakoids of chloroplasts. It is primarily employed in the capture of light-emitted energy. Chlorophyll-a is the primary pigment in plants.

Two Stages:

It is necessary to distinguish between two stages of the photosynthesis process:

• Light-dependent reaction, also known as a light reaction
• Light-independent reaction, also known as a dark reaction

Light Reaction of Photosynthesis (or) Light-dependent Reaction

In the beginning of photosynthesis is the light reaction, which is only carried out during the day in the presence of sunlight. In plants, the light-dependent reaction takes place in the thylakoid membranes of chloroplasts, which are found on the surface of the chloroplasts.

The photosystems, which are membrane-bound sacs-like structures present within the thylakoid, perform their functions by collecting light and are referred to as Grana.

These photosystems contain large complexes of pigment and protein molecules that are present within the plant cells and which play a crucial role during the process of light reactions that occur during photosynthesis, as well as during the process of photosynthesis itself.

Photosystems are classified into two categories: photosystem I and photosystem II.

The light-dependent reactions are those in which the light energy is converted into ATP and NADPH, which are then used in the second phase of photosynthesis to produce energy.

As a result of the light reactions, ATP and NADPH are generated by two electron-transport chains, and water is used as a solvent while oxygen is generated.

For photosynthesis, one can simplify the chemical equation by writing it as follows:

2H2O + 2NADP+ + 3ADP + 3Pi → O2 + 2NADPH + 3ATP

Dark Reaction of Photosynthesis (or) Light-independent Reaction

Carbon-fixing reaction is another name for the dark reaction.

In this process, sugar molecules are formed from water and carbon dioxide molecules, which is not dependent on the presence of light.

The dark reaction takes place in the stroma of the chloroplast, where the NADPH and ATP products of the light reaction are used to fuel the process.

Plants absorb carbon dioxide from the atmosphere through their stomata and then proceed to the Calvin photosynthesis cycle to convert it into sugars.

The Calvin cycle is a chemical reaction in which the ATP and NADPH formed during the light reaction drive the reaction and convert 6 molecules of carbon dioxide into one sugar molecule, also known as glucose, in the presence of oxygen.

The following is a simplified version of the chemical equation for the dark reaction:

3CO2 + 6 NADPH + 5H2O + 9ATP → G3P + 2H+ + 6 NADP+ + 9 ADP + 8 Pi

Importance of Photosynthesis

Photosynthesis is required for the survival of all forms of life on the planet. It plays an important role in the food chain because it is through this process that plants produce their own food, thereby forming the primary producers.

Aside from the production of oxygen, photosynthesis is also responsible for the production of carbon dioxide, which is essential for the survival of most organisms.

Conclusion:

Chlorophyll and other light-sensitive pigments are found in photosynthetic cells, which allow them to capture solar energy. Solvent-free solar cells are capable of converting solar energy into energy-dense organic molecules such as glucose when exposed to carbon dioxide. These cells not only contribute to the global carbon cycle, but they also contribute to the production of a significant portion of the oxygen present in the Earth’s atmosphere. On the surface, non-photosynthesising cells use the products of photosynthesis to perform the opposite of photosynthesis: they break down glucose and release carbon dioxide into the surrounding environment.