Photosynthesis is the process by which green plants use sunlight to convert carbon dioxide and water into glucose and oxygen, making them autotrophs or producers. This process occurs in chloroplasts, involving steps such as water uptake, light absorption, and conversion of raw materials into sugars, and is influenced by factors like light, temperature, carbon dioxide, and water availability. Photosynthesis is crucial for life, as it produces food and oxygen necessary for the survival of all animals.

1. Dipan kundu
Class – VII D
Roll - 15

2. What is photosynthesis?
All organisms need energy to live and grow. This energy is obtained by
the food we eat. Animals get this food by eating plants and other
animals. On the other hand plants can make their own food by the
process of photosynthesis.
Green plants make their own food by the process of photosynthesis.
The process by which green plants make their own food by using the
energy from the sun to convert Carbon Dioxide and water into sugars
also called Glucose in the presence of a green-colored pigment called
Chlorophyll. This process is called photosynthesis.
As they produce their own food they are known as producers or
autotrophs. And their mode of nutrition is called autotrophic nutrition.
The chemical formula of photosynthesis - 6CO2 + 6H2O → C6H12O6 + 6O2
The word formula of photosynthesis is –
Carbon dioxide + Water → Glucose + Oxygen

3. Structure of stomata
Gases are exchanged through small openings present generally on the
lower surface of the leaves are called as Stomata. It is generally present
on the lower surface of the green leaves and on the green stems.
Each stomata has two bean-shaped cells called guard cells. The inner
walls of the guard cells are thicker than the outer walls.
When the guard cells are full of water, they swell and bulge outwards
and the stomata opens. When the guard cells lose water they lose their
turgidity and stomata closes.

4. Raw materials required for
photosynthesis
For Photosynthesis plants require CO2, H2O, light, and C55H72O5N4
 Carbon dioxide: The main source of Carbon dioxide (CO2) for plants is
the atmosphere. The plants takes in carbon dioxide through the
stomata present on the leaves.
 Water: Plants absorb water from the soil through the root hair. This
water is then transported up to the stem and leaves through xylem
vessels.
 Light: Light is very important for photosynthesis. The sun is the
principal source of light energy. You can use any light but light should
be of good intensity.
 Chlorophyll: Chlorophyll is necessary for photosynthesis. Chlorophyll is
present in the green-colored plastids called chloroplasts.

5. Chloroplasts
Chloroplast is a plastid where chlorophyll is present. In chloroplast,
Thylakoids, Granum and Stroma are present.
The inner membrane of a chloroplast is folded into disc-shaped sacs
called Thylakoids.
Chloroplast contain chlorophyll and other pigment which are arranged in
stacks called Granum.
The fluid which is found inside the chloroplast is called Stroma.

6. The process of photosynthesis
Photosynthesis involves in many steps –
 First of all, water is taken up through the root system and C02 reaches
the leaves.
 Light is absorbed by chlorophyll, which splits water and oxygen is
released. This reaction takes place in the thylakoids.
 Then carbon dioxide splits. The carbon which is obtained is used to
make sugars. This reaction takes place in the stroma.
 Then the sugars are transformed into complex sugars. And then
Glucose and Fructose are formed as a result of photosynthesis.

7. Factors affecting photosynthesis
Light, Chlorophyll, Temperature, Carbon dioxide and Water are the main
factors that affect photosynthesis.
 Light: Light energy trapped by the chlorophyll is used to convert raw
materials into sugars.
 Chlorophyll: Chlorophyll is found in structures called chloroplasts. It
enables the plant to trap light energy.
 Temperature: The reaction of photosynthesis can be place in a
suitable temperature that is (20-35)°C.
 Carbon dioxide: The rate of photosynthesis increases with an increase
in the concentration of Carbon dioxide.
 Availability of water: Less than one percent of the total water
absorbed by the plants is utilized as a raw material for
photosynthesis. Therefore, water hardly affects the rate of
photosynthesis.

8. Significance of photosynthesis
Food is produced by the process of photosynthesis. Leaves capture light
energy from the sun and use it to make food. Animals that feed on plants
the energy get passed to the animals and when other animals eat that
plant eating animal the energy get passed to that animal. Like this, the
significance of photosynthesis takes place.
If the process of photosynthesis doesn’t takes place all the animals in the
world will be die in the absence of energy that we get from the food.