Question

Choose the event that does not occur in photosynthesis
A) Absorption of light energy by chlorophyll
B) Reduction of $CO_2$ into carbohydrates
C) Conversion of light energy into chemical energy
D) Oxidation of carbon to $CO_2$

Answer 1

Photosynthesis is the process that is used by green plants, algae, cyanobacteria and also anaerobic organisms to convert light energy into chemical energy that helps the organism to carry out its life processes.

Complete answer:
Photosynthetic organisms are classified into two categories- photoautotrophs, they use sunlight to carry out photosynthesis and use $CO_2$ as the sole carbon source and photoheterotrophs, they do not use $CO_2$ as the carbon source instead they use organic compounds.
Photosynthesis comprises two stages- light dependent reaction and light independent reaction. Light dependant reaction as the name suggests occurs in presence of sunlight, the chlorophyll molecules of the chloroplast absorb the photons that leads to loss of an electron from chlorophyll to pheophytin to a quinone molecule and through the entire electron transport chain to produce NADPH.
The excited chlorophyll returns to ground state by receiving back the lost electron through splitting of water that results in O2 evolution. The light independent reaction utilises this newly formed NADPH to fix $CO_2$ into three carbon sugars that are then converted to sucrose and starch thus acting as food for the plants.

Hence the correct answer is option (D) Oxidation of carbon to $CO_2$.

Note: Photosynthesis is a very important phenomenon that occurs in plants and few other organisms like cyanobacteria and green algae. They help not only in production of food sources for the plant but also release oxygen into the atmosphere which is essential for all aerobic living beings.