Photosynthesis is a fundamental biological process that occurs in plants, algae, and some bacteria. It is the process by which these organisms convert light energy from the sun into chemical energy in the form of glucose (a type of sugar) and oxygen. This process is crucial for the survival of most life on Earth, as it provides the primary source of energy and organic molecules necessary for growth and sustenance.
If we actually start to sit and notice everyday things that take place in the universe, we will surely be dizzy all day! How can we not be? Just look at the plants! They, unlike humans, can’t move, but they make their own food! Isn’t it amazing? Actually, plants make their food with the help of sunlight, water, air and call the process photosynthesis.
In this article, we will be particularly discussing this process called Photosynthesis. If you don’t even have any idea about it, worry not because we got everything covered here!
Read About: Human digestive System
To know what is photosynthesis, we should be knowing that it is made up of two words. What are the two words that make the word photosynthesis? So the question ‘What is Photosynthesis’ can be partially understood by simply dissecting the word ‘Photosynthesis’. Photosynthesis is made up of ‘Photo ( Greek phōs)’ and ‘Synthesis (synthesis)’. With ‘Photo’ in the word Photosynthesis, it is meant light, while ‘Synthesis’ in Photosynthesis means ‘putting together’ or ‘Process’.
Read About: 7 Continents of the World
The formula for photosynthesis is a simplified representation of the process in which green plants, algae, and some bacteria convert carbon dioxide and water into glucose (a sugar) and oxygen using light energy. The overall chemical equation for photosynthesis is:
6 CO2 + 6 H2O + light energy → C6H12O6 (glucose) + 6 O2
In this equation:
- 6 CO2 represents six molecules of carbon dioxide.
- 6 H2O represents six molecules of water.
- Light energy refers to the energy absorbed by chlorophyll and other pigments from sunlight.
- C6H12O6 represents glucose, a simple sugar and the primary product of photosynthesis.
- 6 O2 represents six molecules of oxygen, which are released as a byproduct of the process.
This equation demonstrates the conversion of carbon dioxide and water into glucose and oxygen, driven by the energy of light absorbed by photosynthetic pigments. Photosynthesis is a fundamental process for the production of organic compounds and the release of oxygen into the atmosphere.
Photosynthesis in Higher Plants
In simple terms, the definition of Photosynthesis is the conversion of light energy into chemical energy by plants and other organisms. Chemical energy can be released later to fuel the organism’s activities via cellular respiration, and some of this chemical energy is stored in carbohydrate molecules like sugars and starches. Oxygen is discharged as a waste product, most often. Photosynthesis is carried out by most plants, algae, and cyanobacteria and such organisms are called Photoautotrophs, which are creatures that use light to perform photosynthesis. The production and maintenance of oxygen in the Earth’s atmosphere are mostly due to photosynthesis.
Different species perform photosynthesis in different ways. The process always starts with the absorption of light energy by proteins. Reaction centres are proteins that contain green chlorophyll as well as other coloured pigments/chromophores. These proteins are stored in organelles in plants. Chloroplasts are the name for these organelles. Leaf cells have the highest concentration of chloroplasts. Chloroplasts are incorporated in the plasma membrane of bacteria. Some energy is utilised to extract electrons from appropriate compounds in these light-dependent processes. The hydrogen liberated during the splitting of water is utilised to make two more compounds. Short-term energy storage is provided by the chemicals. Reduced nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine triphosphate (ATP), the “energy currency” of cells, are the molecules in question.
Anoxygenic photosynthetic systems, such as those found in green and purple sulphur bacteria and green and purple nonsulfur bacteria, are likely to have existed in the early stages of evolution. Green sulphur bacteria are likely to have utilised hydrogen and sulphur as electron donors, whereas green nonsulfur bacteria employed different amino and other organic acids. The usage of a variety of nonspecific organic compounds by purple nonsulfur bacteria is compatible with geological evidence indicating Earth’s early atmosphere was strongly reducing at the time.
Oxygenic photosynthesis is the primary source of oxygen in the Earth’s atmosphere. The oxygen disaster is the name given to the first occurrence of this high-energy molecule.
The first photosynthetic organisms most likely developed early in life’s existence. Instead of water, the first photosynthetic organisms most likely utilised reducing chemicals like hydrogen or hydrogen sulphide as electron suppliers. Cyanobacteria appeared after the first photosynthetic organisms, but it was later. Cyanobacteria contributed directly to the oxygenation of the Earth by producing surplus oxygen. It is said to have paved the way for the evolution of sophisticated life. Photosynthesis currently captures around 130 terawatts of energy on a worldwide scale. It consumes around eight times the amount of energy that human civilisation now consumes.
Climate processes rely on photosynthesis. It absorbs carbon dioxide from the atmosphere and subsequently binds it in plants, soils, and harvested products.
Read About: Scientific Name of Pig
Equation of Photosynthesis In Simple words
The overall chemical equation for photosynthesis is:
6 CO2 + 12 H2O + light energy → C6H12O6 (glucose) + 6 O2 + 6 H2O
In this equation, carbon dioxide and water are converted into glucose and oxygen using the energy from sunlight. Photosynthesis is not only essential for plants but also plays a critical role in providing oxygen and food for other organisms in the ecosystem, making it a key process in the global carbon and oxygen cycles.
Photoautotrophs make up the majority of photosynthetic organisms. These organisms can use light energy to directly generate food from carbon dioxide and water. Photoheterotrophs are organisms that utilise carbon dioxide as a supply of carbon atoms in order to carry out photosynthesis. Photoheterotrophs get their carbon from organic substances rather than carbon dioxide. Photosynthesis releases oxygen in plants, algae, and cyanobacteria, and this oxygenic photosynthesis has always been the common type of photosynthesis, which is being used by living organisms. While there are some minor differences between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process in these organisms is quite similar. Anoxygenic photosynthesis comes in a variety of forms.
Carbon dioxide is transformed into sugars in an endothermic redox mechanism known as carbon fixation. Cellular respiration is the polar opposite of photosynthesis. Cellular respiration is the oxidation of carbohydrates or other nutrients to carbon dioxide, while photosynthesis is the conversion of carbon dioxide to carbohydrate. Carbohydrates, amino acids, and fatty acids are among the nutrients used in cellular respiration, and these nutrients are oxidised to produce carbon dioxide and water, as well as chemical energy to drive the organism’s metabolism. As a result, photosynthesis and cellular respiration are two separate processes that occur in different sequences of chemical reactions and in different cellular compartments.
Here’s how photosynthesis works:
- Light Absorption: Photosynthesis begins when light energy is absorbed by pigments in chloroplasts, which are the specialized organelles found in plant cells. The primary pigment responsible for capturing light energy is chlorophyll.
- Light Reaction: In the presence of light, chlorophyll molecules in the chloroplasts become energized. This energy is used to split water molecules (H2O) into oxygen (O2) and protons (H+).
- Electron Transport Chain: The energized electrons from water molecules move through a series of proteins and molecules in the thylakoid membrane of the chloroplast, known as the electron transport chain. This movement of electrons generates ATP (adenosine triphosphate), a molecule that stores and transfers energy.
- Oxygen Production: During the electron transport chain, oxygen is released as a byproduct when water molecules are split.
- Carbon Fixation: In the next phase, known as the Calvin cycle (or the dark reaction), carbon dioxide (CO2) from the atmosphere is fixed into a three-carbon compound known as 3-phosphoglycerate (3-PGA). This reaction is catalyzed by an enzyme called ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO).
- Reduction and Sugar Production: ATP and NADPH, which were generated in the light reaction, are used to convert 3-PGA into a three-carbon sugar molecule, glyceraldehyde-3-phosphate (G3P). Some of the G3P molecules are used to regenerate RuBisCO and continue the Calvin cycle, while others are used to produce glucose and other organic compounds, which serve as an energy source and building blocks for plant growth.
- Oxygen Release: Oxygen produced in the light reaction is released into the atmosphere as a waste product.