What Is Photosynthesis in Biology

What is the Site of Photosynthesis?

Chlorophyll present in the plants makes the plant look green, which is present in chloroplasts. Hence, a chloroplast is the site of photosynthesis. A standard chloroplast is of discoid shape in the plants. 

All green parts of a plant take part in the process of photosynthesis. Let's say if the stem of a plant is green, it will perform the photosynthesis process as well. But out of all of the parts, the leaves play the most significant organs of photosynthesis. So, leaves are recognised as the food factories of green plants because photosynthesis process takes place in them. Just one square millimetre of a leaf consists of a half a million chloroplasts in it. It means around 4 - 6 micron. 

About Site of Photosynthesis - Chloroplasts

All plants, algae, and certain microorganisms perform this important photosynthesis process.  Photosynthesis reaction happens specifically, in the grana and stroma regions of chloroplasts. The stroma includes circular RNA, DNA, and enzymes that help in starch synthesis in plants. This stroma also consists of many grana, and each granum holds many disc-shaped membranes. These disc-shaped structures look like a stack of coins and are called thylakoids. One chloroplast has 40 to 60 grana. In this grana, photosynthetic pigments are present. 

Photosynthesis Process

Many of us think that we are feeding the plant by putting the soil in a plant, exposing it to the sun, and watering it. However, the reality is different; these sources are not real foods for plants.

Plants are also scientifically known as autotrophs because they are capable of utilising energy from light to synthesise. In this way, plants can produce their own food called starch or glucose. The plants make glucose by using water, sunlight, and the gases present in the atmosphere. This glucose is a kind of sugar that helps plants to stay alive. In return, plants release oxygen in the environment that is a byproduct of photosynthetic reactions. 

This whole process of converting light energy into chemical energy is called photosynthesis. In simple terms, photosynthesis absorbs carbon dioxide and emits oxygen in the air. Thus, photosynthesis helps in the maintenance of carbon dioxide and oxygen balance in the environment too. 

Importance of Photosynthesis in Life

Without photosynthesis, life on the Earth can come to hold as it plays one of the most crucial roles in the lifecycle of plants. It is vital for the survival of the large majority of life in the world. Through this process, practically every kind of energy found in the biosphere becomes accessible to living organisms. It is the base of Earth's food source that is consumed directly or indirectly by all living things. Furthermore, the oxygen we get to breathe from the atmosphere comes because of the photosynthesis process.

Hence, no photosynthesis can lead to little to no food, and the majority of the organisms would disappear from the Earth as eventually there will be no oxygen gas in the environment.

Food Production in Plants

Leaves comprise a lot of tiny pore-like structures in their below surface that are called stomata. The leaves absorb carbon dioxide from the air through the stomata. Further, hair-like pipelines present in the roots and all through the plant help to transport water and minerals in it. These pipelines are a type of tissues called xylem. 

A green pigment called chlorophyll is found in the site of photosynthesis - chloroplast that absorbs sunlight and produces energy. Carbohydrate produced acts as food for plants that eventually turns into starch and stores in leaves. Thus, starch is a kind of carbohydrate. Further, the starch transports from leaves to other parts of a plant. Also, oxygen emits in the air through stomata during this process. 

(Image to be added soon)

(Plant using sunlight, water and carbon dioxide during photosynthesis to produce carbohydrate and oxygen.)

Equation of Photosynthesis Process

The photosynthesis process is supposed to be an endothermic reaction. Water and carbon dioxide are the two reactants involved in the photosynthesis reaction that produces two products, i.e., glucose as well as oxygen. 

Here is an equation for photosynthesis

6CO2 + 6H2O→ C6H12O6 + 6O2

Types of Photosynthesis

There are two types of photosynthesis whose general principles regarding the photosynthetic process are quite the same. Let's know about them and what makes them different from each other.

• Oxygenic Photosynthesis 

Oxygenic photosynthesis is widely seen in plants, cyanobacteria, and algae. It is one of those types of photosynthesis that counterbalances the respiratory system of the environment. The oxygenic photosynthesis uses the carbon dioxide created in the atmosphere by all breathing organisms and releases oxygen into it.

In this reaction, electrons from water (H2O) are transformed by the light energy into carbon dioxide (CO2). As a result, plants produce carbohydrates. During this transfer process, the water gets oxidised or loses electrons, and carbon dioxide diminishes or receives electrons. Thus, oxygen and carbohydrates are produced.

The chemical equation for oxygenic photosynthesis is

6CO2 + 12H2O + Light Energy → C6H12O6 + 6O2 + 6H2O

• Anoxygenic Photosynthesis

In the anoxygenic photosynthetic process, electron donors are used along with water. This type of photosynthesis reaction is generally found in microorganisms like green sulfur bacteria or purple bacteria. These kinds of bacteria are common in many aquatic habitats.

As the name suggests, anoxygenic photosynthesis doesn't generate oxygen. However, the byproduct of this type of photosynthesis process relies upon its electron donor.