Question

Write a note on oxygen cycle.

Answer 1

Oxygen cycle

• Atmospheric oxygen is used by all living beings for respiration. During respiration, glucose reacts with oxygen to produce carbon dioxide and water and to give energy.

$$\begin{gathered} {\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{s}\right)+6{\mathrm{O}}_2\left(\mathrm{g}\right)\to 6{\mathrm{CO}}_2\left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O}+\mathrm{energy} \\ \mathrm{Glucose}\mathrm{Oxygen}\mathrm{Carbon}\mathrm{dioxide}\mathrm{Water} \end{gathered}$$

• Oxygen is also used for the combustion of fuels like petrol, diesel, etc. Aquatic animals use the oxygen dissolved in water.
• The oxygen which is used for carrying our various processes is replenished by green plants through photosynthesis.
• Photosynthesis is the process through which green plants prepare their own food using carbon dioxide and water in the presence of sunlight.
• During the process, carbon dioxide present in the atmosphere is used by the plants and oxygen is released into the atmosphere.
• Photosynthesis can be represented through the following equation.

$$\begin{gathered} 6{\mathrm{CO}}_2\left(\mathrm{g}\right)+6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\underset{\mathrm{chlorophyll}}{\overset{\mathrm{sunlight}}{\to }}{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{s}\right)+6{\mathrm{O}}_2\left(\mathrm{g}\right) \\ \mathrm{Carbon}\mathrm{dioxide}\mathrm{Water}\mathrm{Glucose}\mathrm{Oxygen} \end{gathered}$$

• Oxygen and carbon dioxide are balanced in nature as they are being continuously consumed and produced. This circulation of oxygen in nature is known as oxygen cycle.