Question

What is the function of RuBP?

Answer 1

Hint: Photorespiration is the process of uptake of oxygen and production of carbon dioxide in light by the photosynthesizing tissues. This term was proposed by Dicker and Tio in the year 1959, they observed that the respiration rate of green plants is higher in light as compared to the dark.

Complete answer:
Photorespiration is an integral and inseparable aspect of photosynthesis. RUBP carboxylase is the main enzyme of dark reaction and also catalyses another reaction which interferes with the functioning of the Calvin cycle.
When the temperature and oxygen concentration increases, RUBP carboxylase shows greater affinity to oxygen as compared to carbon dioxide. Therefore, in presence of higher concentration of oxygen and high temperature, RUBP acts as oxygenase and converts RUBP (ribulose 1,5 bisphosphate) to 3-carbon compound phosphoglyceric acid (PGA) and a 2-carbon compound phosphoglycolate. The phosphoglycolate is quickly converted to glycolate or glycolic acid. These reactions can take place in chloroplasts. It is the primary acceptor of carbon dioxide.
Photorespiration process occurs mainly in the temperate plants, for example- beet, bean, cotton, rice, wheat, barley, etc. It increases with increase of temperature, intensity of light, concentration of oxygen, age of the leaf.

Note:
Photorespiration has no relation with normal respiration, which occurs throughout the day and night in all the types of living cells. The normal respiration is often called dark respiration.
The end products of dark respiration are CO₂ and water. It occurs mainly in cytoplasm and mitochondria and produces energy for the maintenance of cells, synthesis and work. It is not changed by the change in oxygen concentration.