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Comparison of Photosynthesis and Respiration

Updated on October 10, 2015

Let’s Compare Photosynthesis to Respiration

Living forms have some basic processes which help in the survival and perpetuation of its race, called the life processes. Photosynthesis and Respiration are two important life processes. Photosynthesis takes place in plants and respiration takes place in all the organisms including plants. We know very well that we get our food due to the process of photosynthesis. Plants add oxygen to the atmosphere which makes our living possible. Respiration plays an important role in releasing the energy and providing the suitable air (Oxygen / CO2) to live. Lets see the comparison between photosynthesis and respiration in this lesson.
Occurrence of Photosynthesis:
Photosynthesis occurs in plants and a few other bacteria.
Occurrence of Respiration:
Respiration Occurs in all living organisms.

Photosynthesis and its significance:
Food is prepared in the process of photosynthesis. The prepared carbohydrates are assimilated. This process takes place in chloroplasts where simple inorganic substances like CO2 and water are converted into glucose. The plants use the essential factors, trap light energy to form high energy bonds.
Respiration and its significance:
The food is broken down into simple molecules to release the energy stored in the food material.
This process takes place in cytoplasm and mitochondria.
Molecules like glucose are oxidized to release CO2 and Water. Oxygen is the prime requirement for the process of oxidation to take place.


This is a constructive or anabolic process.
This is a catabolic process
Simple inorganic substances are converted into glucose.
Complex molecules are broken down.
Water molecule is broken down. The end products of respiration are the
Water molecule is formed The end products of photosynthesis are
starting material.
the starting material
(CO2 and Water)
(Carbohydrates and O2)
Needs sunlight
Doesn't need sunlight
Takes Place in the presence of sunlight
Takes place through out the day.
  • We can remember that when a potted plant is kept in a closed room for a day, its leaves show zero presence of starch. But the plant doesn't die. When it is kept in sunlight again, it regains its metabolic activities.
  • Whereas if you put a cockroach in a closed bottle, it dies after few minutes due to lack of oxygen.
  • So, we can say that a plant can survive without performing photosynthesis for few days. But no organism can survive without respiration for few minutes.
  • Does all the parts of a plant perform the process of photosynthesis? No. Only leaves perform this process. Where as all living cells of an organism performs the process of respiration.
  • There is no photosynthesis, if there is no light. Respiration doesn't require light. Light energy is fixed during photosynthesis but the energy is released in respiration.

Raw materials required:
Photosynthesis requires CO2, Water and Sunlight to undergo the process.
Respiration requires carbohydrates and oxygen to undergo the process.
In both these processes, ATP is produced. plants produce ATP by using light energy (through photophosphorylation). ATP is produced in the process of respiration by oxidation of glucose (through oxidative phosphorylation).

A Simple Comparison is as follows:

Produces food
Consumes food
Stores energy
Releases Energy
Consumes H2O
Produces H2O
Consumes CO2
Produces CO2
Releases O2
Consumes O2
Light - dependent
Light - independent

As food is prepared due to the Process of Photosynthesis, we can say that it adds weight to the organism (biomass to the organism).
As the complex molecules are broken down in this process, we can say that it decreases the weight of the organism.
Both plants and animals require respiration because it is the process in which food is converted into energy in the form of ATP, which is used for many processes within all organisms.
We can say that both reactions transform energy in one way or another - either storing it or releasing it.
Oxygen produced during photosynthesis replenishes the oxygen that was used up by the living organisms during respiration.
The cycle of photosynthesis and respiration maintains the balance of carbon dioxide and oxygen on earth.


→ Converts radiant light energy into Chemical energy.
→Releases Chemical or Potential energy for several other functions
→ NADP is reduced to NADPH2 using hydrogen of water molecule
→ NADH2 is formed from hydrogen of Carbohydrates
→ Organic compounds are synthesized using ATP and NADPH2
→ Cellular activities take place in the pre sense of NADH2 and ATP
→ Oxygen is released
→ Oxygen is consumed


6 CO2 + 12 H2O ---------------> C6H12O6 + 6 O2 + 6 H2O

C6H12O6 + 6 O2 ----------------> 6 CO2 + 6 H2O + 686K. cal


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