Photosynthesis and respiration

Photosynthesis

Photosynthesis is a biochemical process through which green plants, some algae, and certain bacteria absorb sunlight and convert it into chemical energy stored in glucose.
The general equation for photosynthesis is 6CO2 + 6H2O + Light Energy → C6H12O6 + 6O2, illustrating the conversion of carbon dioxide and water, in the presence of light energy, into glucose and oxygen.
This process occurs in the plant’s chloroplasts, specifically within the pigment called chlorophyll.
Photosynthesis comprises two principal stages: Light-dependent reactions and Light-independent reactions.
Light-dependent reactions occur in the thylakoid membranes of the chloroplasts where sunlight (light energy) splits water molecules into oxygen, hydrogen ions, and electrons to form ATP (a molecule that stores and transfers energy in cells) and NADPH. ATP and NADPH are essential energy carriers needed for the second stage of photosynthesis.
Light-independent reactions, also known as the Calvin cycle, take place in the stroma, using the ATP and NADPH produced from the first stage and carbon dioxide from the atmosphere to create glucose.

Respiration

Respiration is the process by which plants (as well as animals and microbes) convert the energy stored in glucose into a form which can be easily used by cells. This process results in the production of carbon dioxide, water and energy (ATP).
The equation for respiration is C6H12O6 + 6O2 → 6CO2 +6H2O + Energy, in essence the reverse of the photosynthesis equation.
Respiration occurs in all living cells of the plant, not just in certain areas like photosynthesis.
There are two types of respiration: Aerobic respiration and Anaerobic respiration.
Aerobic respiration refers to the process where oxygen is used to break down glucose to produce ATP. Aerobic respiration is extremely efficient and can produce up to 38 ATPs per glucose molecule.
Anaerobic respiration, also known as fermentation, takes place when there is insufficient oxygen available. This process is less efficient, creating just 2 ATPs per glucose molecule, and also produces by-products such as ethanol in yeast cells and lactic acid in muscle cells.

Connection Between Photosynthesis and Respiration

There is a reciprocal relationship between photosynthesis and respiration in plants. While photosynthesis absorbs carbon dioxide and releases oxygen to the atmosphere, respiration does exactly the opposite.
The glucose produced in photosynthesis is the primary resource utilised in respiration to produce energy.
Thus, photosynthesis and respiration are complementary processes that cycle carbon, water and oxygen through the ecosystem.