Distinguish between
(a)Respiration and photorespiration.
(b) Cyclic photophosphorylation and non-cyclic photophosphorylation.

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Solution

(a) Difference between Respiration and photorespiration
Respiration Photorespiration
It occurs in all living cells. It occurs only inside photosynthetic cells.
It continues in both dark and light. It takes place only in the presence of light.
It occurs in all organisms. It occurs in $C_{3}$ plants and negligible in $C_{4}$ plants.
Exchange of gases is not dependent on light. Exchange of gases are light dependent.
It is not affected by change in oxygen concentration between 10-25%. Beyond it there is a decline in the rate of respiration. It increases with the the increase in oxygen concentration.
It takes place in cytoplasm and mitochondria. It takes place in chloroplasts and may require the help of perioxisomes and mitochondria.
Glucose is used as substrate for respiration. RuBP is used as substrate for photorespiration.
$C O_{2}$ and water are end products. $C O_{2}$ and PGA are end products.
The end products are not recycled in respiration. Both the end products are reutilized in photosynthesis.
It is an useful process as it produces energy. It is a wasteful process as it does not produce energy.
(b) Difference between Cyclic photophosphorylation and Non-cyclic photophosphorylation
Cyclic photophosphorylation Non-cyclic photophosphorylation
It is performed by photosystem I independently. It is performed by collaboration of both photosystems II and I.
An external source of electrons is not required. The process requires an external electron donor.
It is not connected with photolysis of water. Therefore, no oxygen is evolved. It is connected with photolysis of water and liberation of oxygen occurs.
It synthesises ATP only. It is not only connected with ATP synthesis, but also with production of NADPH.
It operates under low light intensity, anaerobic conditions or when $C O_{2}$ availability is poor. It takes place under optimum light, aerobic conditions and in the presence of carbon dioxide.
The system does not take part in photosynthesis except in certain bacteria. The system is connected with $C O_{2}$ fixation in green plants.
It occurs mostly in stroma lamellae membrane. It occurs in the granal thylakoids.

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