Photosynthesis

Definition and Importance

Photosynthesis is the process by which green plants, algae and some types of bacteria convert light energy, usually from the sun, into chemical energy in the form of glucose.
It is critically important because it is the primary source of food for almost all life forms; even humans, who consume plants (or animals that have eaten plants) rely on photosynthesis.
Photosynthesis is also the process by which atmospheric carbon dioxide is reduced and oxygen is produced, maintaining the balance of gases in the atmosphere.

Photosynthesis Equation

The general equation for photosynthesis is: 6CO2 + 6H2O -> C6H12O6 + 6O2.
This equation signifies that carbon dioxide and water, in the presence of light energy, are converted into glucose and oxygen.

Light-Dependent Reactions

The light-dependent reactions happen in the thylakoid membrane and are powered by light energy.
Chlorophyll, the green pigment found in chloroplasts, absorbs light and uses this energy to split water molecules into hydrogen and oxygen.
The liberated oxygen gets released into the atmosphere, whilst the hydrogen is used in the next stage of photosynthesis.

Light-Independent Reactions: The Calvin Cycle

The Calvin Cycle are the light-independent reactions of photosynthesis, which occur in the stroma of the chloroplasts.
They utilise the hydrogen from the light-dependent reactions and combine it with carbon dioxide from the atmosphere to produce glucose.
Glucose, being a complex carbohydrate, is an energy-rich substance that plants use for their growth and development.

Factors Affecting Photosynthesis

Light intensity, the concentration of carbon dioxide and temperature are the three main factors that can impact the rate of photosynthesis.
Generally, the rate of photosynthesis will increase as light intensity and carbon dioxide concentration increase (up to a point), but if the temperature gets too high or low, the rate can slow down due to enzyme activity being affected.
Plants have adaptations, like the ability to adjust the opening and closing of stomata, to control gas exchange and deal with changes in these factors.

Remember, photosynthesis is a complex biochemical process that powers life on Earth. Understanding it can aid in comprehending many other biological topics.