Category: Biology Second Paper

In 1986, Devlin proved that the process of photosynthesis takes place in the chloroplast. For this he called chloroplast as Photosynthetic apparatus. Photosynthesis occurs in the mesophyll tissue of plant leaves. Photoneutral reactions occur in the stroma of chloroplasts and photoreactions occur in quantosomes. A quantosome contains 250 chlorophylls, enzymes, electrons and pigments. Photosynthesis takes place in the green leaves of higher plants, flower petals and peduncles, green skin of flowers and fruits. Bacteria, cyanobacteria, red and brown algae carry out photosynthesis (chemosynthesis) with chromatophores. Photosynthesis occurs in the leaves and young stems of higher plants. Algae and bryophytes have chloroplasts throughout their bodies and carry out photosynthesis. Green leaves have the most chloroplasts. So green leaves are the main part of photosynthesis
is identified as Aquatic plants have a high rate of photosynthesis due to the high amount of dissolved CO2 in the water. Unicellular organisms like Euglena, Crysamoeba etc. carry out photosynthesis due to the presence of chlorophyll. The amount of CO2 in the atmosphere is 0.03% and that of water is 0.3%. Although Mucor, Yeast, Agaricus etc. are plants, they cannot carry out photosynthesis due to lack of pigments.
[ Organelles of Photosynthesis-Green Leaves, Organelles of Photosynthesis-Chloroplasts and Organelles of Photosynthesis-Thylakoids]

1. A universal energy storage compound
2. The universal molecule of energy transfer
3. The energy currency of the cell
4. The coin of the cell’s energy transfer
5. Biological coin or Energy coin.

ATP is a high-energy chemical substance. ATP is produced by the addition of ADP and Pi by the action of the ATP-ase enzyme. The process of making ATP is called phosphorylation. ATP is produced in the part of the thylakoid that faces the surface stroma. ATP is the source of chemical energy in living cells. ATP stores a lot of energy. ATP provides the energy required for various cell reactions. So ATP is called biological coin or energy coin or molecular currency. British biochemist Peter Michel proposed oxidative phosphorylation as the process of making ATP.

In the process of photolysis, water molecules are broken down to produce oxygen, hydrogen and electrons. Electricity or fuel produced directly from hydrogen and electrons is called green energy. In 2011, scientists at the Massachusetts Institute of Technology created an artificial leaf. Place the artificial leaf in water in the presence of sunlight. Electricity or fuel is generated by breaking water molecules under the influence of light to form hydrogen and oxygen gas. Attempts are being made to make electricity or fuel by directly using hydrogen and oxygen created from water in natural ways.

1. O2 produced in photolysis enters the atmosphere and balances the environment.
2. The electrons produced in this process fill the electron deficiency of the photosystem.
3. NADPH+H+ is produced in this process.
4. The energy generated in this process produces carbohydrates in the neutral phase of light.

Chlorophyll that loses electrons undergoes photolysis or oxidation of water molecules to regain electrons. The proton combines with NADP to yield the assimilation energy NADPH+H+. If photolysis does not occur, assimilation energy will not be produced. The most powerful oxidant in biology is P680+.
With the help of enzymes, Mn++ and Cl- ions, two molecules of water (2H2O) are decomposed to produce four protons (4H+), four electrons (4e-) and one molecule of oxygen (O2).
In water NADH+H+ to e- combines spontaneously with oxygen to form water. In the process of photosynthesis, electrons move from water to NADP+ under the influence of energy. Water is produced from high energy NADH+H+ in plants. Again, high energy NADH+H+ is produced from low energy water in photosynthesis process. Oxygen and H+ are produced as byproducts. When the body lacks oxygen, nerve cells die first. Water splitting occurs only in the presence of light hence the name photolysis.

The breaking down of water molecules in the presence of light to produce oxygen (O2), protons (H+) and electrons (e-) is called photolysis. This is also called photo oxidation.

The unit of photosynthesis is the photosynthetic unit. Thylakoids contain photosynthetic units. The photosynthetic unit consists of 300-400 molecules of chlorophyll-a, chlorophyll-b, carotene and xanthophyll. It contains various enzymes, phospholipids, sulfolipids, metal ions, quinones, etc. Photosynthetic units absorb light energy and cause photophosphorylation.

Photosynthesis occurs only in the presence of sunlight. So the process of photosynthesis takes place during the day. However, photosynthesis is possible even with the application of artificial light.

In 1727, Stephen Hales suggested that plants take nutrients from the air with the help of leaves. In 1905, Blackman divided the photosynthesis process into light and dark stages. In 1931, scientist Van Niel discovered the similarity between photosynthesis in green plants and bacteria. In 1937, scientist Robin Hill proved that water is the source of O2 released in the process of photosynthesis. In 1941 Ruben, Kamen and Randall proved the source of O2 using isotopes. Calvin, Basham and Benson discovered the C3 cycle in 1954. Hatch and Slack discovered the C4 cycle in 1966.