Photosynthesis

Have you heard about the word photosynthesis in your science textbooks? Plants do not eat food that is provided by someone else; they make their own food by the photosynthesis process. If you understand what photosynthesis is, you will be able to know a lot about the cellular and chemical activities taking place in plant bodies.

What is Photosynthesis in Biology?

The word photosynthesis comes from two Greek words, fos (light), and synthesis (combining). The photosynthesis definition says that it is a combination of plant food's creation with the help of light.

Photosynthesis reaction occurs in green plants, and in some prokaryotes, purple bacteria, and green sulfur bacteria. The photosynthesis process in all of them is similar.

Where Does this Process Occur?

In plants and blue-green algae, the photosynthesis process takes place in chloroplasts. The chloroplast is present in all green parts of a plant – the leaves, green stems, sepals, and even in the flowers, in the form of green colour plastids. The chloroplast is found only in plant cells and is essential for photosynthesis reaction.

Factors Affecting Photosynthesis

Various factors influence/affect the photosynthesis process. These are:

  • Light Intensity: More the light, the more will be the rate of photosynthesis. Similarly, low light will lead to a low rate of photosynthesis.

  • The Concentration of CO2: A higher CO2 concentration rate in a plant also accelerates the photosynthesis process. The required amount of CO2 is 300-400 PPM.

  • Temperature: If the temperature is between the range of 25 to 35 degrees Celsius, the photosynthesis takes place effectively.

  • Water: An essential amount of water is required for stomatal opening, and it’s a key factor in the process of photosynthesis.

  • Pollution: The increasing rate of polluting particles in the atmosphere block the pores of somatic cells, and the intake of carbon dioxide becomes difficult.


Photosynthesis Equation

Carbon dioxide and water are the two major factors involved in the photosynthesis reaction. It’s an endothermic reaction, and the products resulting from it are oxygen and glucose. The formula is:

6CO2 + 6H2O = C6H12O6 + 6O2

However, some bacteria don’t produce oxygen as a by-product of photosynthesis. They are called anoxygenic photosynthetic bacteria, and those who do it are called oxygenic photosynthetic bacteria.

Photosynthetic Pigments

Four types of photosynthetic pigments are present in the leaves of the plants. They are:

1. Chlorophyll a

2. chlorophyll b

3. xanthophylls

4. Carotenoids

Structure of Chlorophyll

Chlorophyll is a green colour pigment found in plants that play a vital role in photosynthesis. It allows the plants to absorb the energy coming from the sunlight, which is essential for photosynthesis.

Process of Photosynthesis

The photosynthesis process occurs in plants. It takes place in chloroplasts at the cellular level that contains the chlorophyll. Leaves have parts called petiole, epidermis, and a lamina that absorbs sunlight.

Photosynthesis Steps:

The photosynthesis process takes place at two levels or steps. These are:

Light Reaction of Photosynthesis (or) Light-dependent Reaction

The process begins in the daylight, by gathering the light. The two types of photosystems convert light energy into ATP and NADPH. During their conversion, oxygen is produced, and water is used. The equation of this step is:

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

The Dark Reaction of Photosynthesis (or) Light-independent Reaction

This is also called carbon-fixing. It is not dependent on light and takes place in chloroplast where the products from the earlier step are used. Plants intake the CO2 and the Calvin Photosynthesis Cycle begins, where the six molecules of CO2 are converted into sugar or glucose.

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

Importance of Photosynthesis

The photosynthesis process is very important for the survival of living beings, and to continue the food chain. It also produces oxygen, which is required for breathing.

FAQ (Frequently Asked Questions)

1. What is Photosynthesis?

The process by plants, of producing nutrients essential for survival.

2. What happens in a Photosynthesis Process?

The nutrients and glucose required for plants, and oxygen required for the animals, is created during the process.

3. What is the Photosynthesis Reaction?

A reaction taking place in plants that results in the production of glucose and oxygen.

4. What is Shown in a Photosynthesis Diagram?

The photosynthesis diagram shows how the plants take sunlight and use it to produce essential nutrients and oxygen.

5. Why is Photosynthesis in Plants Important?

It helps in the survival of the plants, the creation of products essential for the survival of living beings, and also to maintain the environmental balance.

6. How Long is the Photosynthesis Cycle?

The whole process of photosynthesis, right from absorbing the light up to the final stage, takes place in just 30 seconds!

7. What is Included in the Mechanism of Photosynthesis?

The mechanism of photosynthesis is an oxidation (oxygen releasing) and reduction reaction. It produces glucose along with oxygen.